ANSYS Fluent Tutorial Guide
ANSYS, Inc.
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January 2021
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Table of Contents
Using This Manual .................................................................................................................................... xxiii
1. What’s In This Manual ...................................................................................................................... xxiii
2. How To Use This Manual .................................................................................................................. xxiii
2.1. For the Beginner ..................................................................................................................... xxiii
2.2. For the Experienced User ........................................................................................................ xxiii
3. Typographical Conventions Used In This Manual .............................................................................. xxiii
1. Fluid Flow in an Exhaust Manifold .......................................................................................................... 1
1.1. Introduction ..................................................................................................................................... 1
1.2. Prerequisites ..................................................................................................................................... 2
1.3. Problem Description ......................................................................................................................... 2
1.4. Setup and Solution ........................................................................................................................... 2
1.4.1. Preparation .............................................................................................................................. 3
1.4.2. Meshing Workflow ................................................................................................................... 3
1.4.3. General Settings ..................................................................................................................... 15
1.4.4. Solver Settings ....................................................................................................................... 16
1.4.5. Models ................................................................................................................................... 17
1.4.6. Materials ................................................................................................................................ 18
1.4.7. Cell Zone Conditions .............................................................................................................. 19
1.4.8. Boundary Conditions ............................................................................................................. 19
1.4.9. Solution ................................................................................................................................. 23
1.5. Postprocessing ............................................................................................................................... 31
1.6. Summary ........................................................................................................................................ 44
2. Fluent Postprocessing : Exhaust Manifold ............................................................................................ 45
2.1. Introduction ................................................................................................................................... 45
2.2. Prerequisites ................................................................................................................................... 46
2.3. Problem Description ....................................................................................................................... 46
2.4. Setup and Solution ......................................................................................................................... 46
2.4.1. Preparation ............................................................................................................................ 47
2.4.2. Reading the Mesh .................................................................................................................. 47
2.4.3. Manipulating the Mesh in the Viewer ...................................................................................... 47
2.4.4. Adding Lights ........................................................................................................................ 49
2.4.5. Creating Isosurfaces ............................................................................................................... 53
2.4.6. Generating Contours .............................................................................................................. 56
2.4.7. Generating Velocity Vectors .................................................................................................... 60
2.4.8. Creating an Animation ........................................................................................................... 64
2.4.9. Creating a Scene With Multiple Graphics Features ................................................................... 69
2.4.10. Creating Exploded Views ...................................................................................................... 71
2.4.11. Animating the Display of Results in Successive Streamwise Planes ......................................... 74
2.4.12. Generating XY Plots .............................................................................................................. 77
2.4.13. Creating Annotation ............................................................................................................. 80
2.4.14. Saving Picture Files ............................................................................................................... 82
2.4.15. Generating Volume Integral Reports ..................................................................................... 82
2.5. Summary ........................................................................................................................................ 83
3. Modeling Flow Through Porous Media ................................................................................................. 85
3.1. Introduction ................................................................................................................................... 85
3.2. Prerequisites ................................................................................................................................... 86
3.3. Problem Description ....................................................................................................................... 86
3.4. Setup and Solution ......................................................................................................................... 87
3.4.1. Preparation ............................................................................................................................ 87
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3.4.2. Meshing Workflow ................................................................................................................. 87
3.4.3. General Settings ................................................................................................................... 103
3.4.4. Solver Settings ..................................................................................................................... 105
3.4.5. Models ................................................................................................................................. 106
3.4.6. Materials .............................................................................................................................. 107
3.4.7. Cell Zone Conditions ............................................................................................................ 108
3.4.8. Boundary Conditions ............................................................................................................ 112
3.4.9. Solution ............................................................................................................................... 114
3.4.10. Postprocessing ................................................................................................................... 119
3.5. Summary ...................................................................................................................................... 131
4. Modeling External Compressible Flow ............................................................................................... 133
4.1. Introduction ................................................................................................................................. 133
4.2. Prerequisites ................................................................................................................................. 133
4.3. Problem Description ..................................................................................................................... 134
4.4. Setup and Solution ....................................................................................................................... 135
4.4.1. Preparation .......................................................................................................................... 136
4.4.2. Meshing Workflow ............................................................................................................... 136
4.4.3. Mesh .................................................................................................................................... 149
4.4.4. Solver .................................................................................................................................. 151
4.4.5. Models ................................................................................................................................. 152
4.4.6. Materials .............................................................................................................................. 154
4.4.7. Boundary Conditions ............................................................................................................ 155
4.4.8. Operating Conditions ........................................................................................................... 158
4.4.9. Reference Values .................................................................................................................. 159
4.4.10. Solution ............................................................................................................................. 160
4.4.11. Postprocessing ................................................................................................................... 164
4.5. Summary ...................................................................................................................................... 177
5. Fluid Flow and Heat Transfer in a Mixing Elbow ................................................................................. 179
5.1. Introduction ................................................................................................................................. 179
5.2. Prerequisites ................................................................................................................................. 180
5.3. Problem Description ..................................................................................................................... 180
5.4. Setup and Solution ....................................................................................................................... 181
5.4.1. Preparation .......................................................................................................................... 182
5.4.2. Launching ANSYS Fluent ...................................................................................................... 182
5.4.3. Meshing Workflow ............................................................................................................... 185
5.4.4. Setting Up Domain ............................................................................................................... 195
5.4.5. Setting Up Physics ................................................................................................................ 197
5.4.6. Solving ................................................................................................................................ 209
5.4.7. Displaying the Preliminary Solution ...................................................................................... 220
5.4.8. Adapting the Mesh ............................................................................................................... 234
5.5. Summary ...................................................................................................................................... 247
6. Exhaust System: Fault-tolerant Meshing ............................................................................................ 249
6.1. Introduction ................................................................................................................................. 249
6.2. Prerequisites ................................................................................................................................. 250
6.3. Problem Description ..................................................................................................................... 250
6.4. Setup and Solution ....................................................................................................................... 250
6.4.1. Preparation .......................................................................................................................... 251
6.4.2. Geometry and Mesh ............................................................................................................. 251
6.4.3. General Settings ................................................................................................................... 273
6.4.4. Solver Settings ..................................................................................................................... 274
6.4.5. Models ................................................................................................................................. 275
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6.4.6. Materials .............................................................................................................................. 276
6.4.7. Cell Zone Conditions ............................................................................................................ 276
6.4.8. Boundary Conditions ............................................................................................................ 276
6.4.9. Solution ............................................................................................................................... 278
6.4.10. Postprocessing ................................................................................................................... 284
6.5. Summary ...................................................................................................................................... 290
7. Modeling Hypersonic Flow ................................................................................................................. 291
7.1. Introduction ................................................................................................................................. 291
7.2. Prerequisites ................................................................................................................................. 291
7.3. Problem Description ..................................................................................................................... 291
7.4. Setup and Solution ....................................................................................................................... 292
7.4.1. Preparation .......................................................................................................................... 292
7.4.2. Meshing Workflow ............................................................................................................... 293
7.4.3. Mesh .................................................................................................................................... 306
7.4.4. Solver .................................................................................................................................. 307
7.4.5. Models ................................................................................................................................. 308
7.4.6. Materials .............................................................................................................................. 310
7.4.7. Operating Conditions ........................................................................................................... 311
7.4.8. Boundary Conditions ............................................................................................................ 311
7.4.9. Solution ............................................................................................................................... 316
7.4.10. Postprocessing ................................................................................................................... 326
7.5. Summary ...................................................................................................................................... 333
8. Modeling Transient Compressible Flow .............................................................................................. 335
8.1. Introduction ................................................................................................................................. 335
8.2. Prerequisites ................................................................................................................................. 335
8.3. Problem Description ..................................................................................................................... 335
8.4. Setup and Solution ....................................................................................................................... 336
8.4.1. Preparation .......................................................................................................................... 336
8.4.2. Reading and Checking the Mesh ........................................................................................... 337
8.4.3. Solution ............................................................................................................................... 339
8.4.4. Models ................................................................................................................................. 340
8.4.5. Materials .............................................................................................................................. 341
8.4.6. Operating Conditions ........................................................................................................... 342
8.4.7. Boundary Conditions ............................................................................................................ 343
8.4.8. Solution: Steady Flow ........................................................................................................... 347
8.4.9. Enabling Time Dependence and Setting Transient Conditions ............................................... 364
8.4.10. Specifying Solution Parameters for Transient Flow and Solving ............................................ 366
8.4.11. Saving and Postprocessing Time-Dependent Data Sets ....................................................... 369
8.5. Summary ...................................................................................................................................... 382
9. Using the Frozen Rotor Method .......................................................................................................... 383
9.1. Introduction ................................................................................................................................. 383
9.2. Prerequisites ................................................................................................................................. 383
9.3. Problem Description ..................................................................................................................... 383
9.4. Setup and Solution ....................................................................................................................... 384
9.4.1. Preparation .......................................................................................................................... 385
9.4.2. Mesh .................................................................................................................................... 385
9.4.3. Models ................................................................................................................................. 385
9.4.4. Materials .............................................................................................................................. 386
9.4.5. Cell Zone Conditions ............................................................................................................ 386
9.4.6. Boundary Conditions ............................................................................................................ 387
9.4.7.Turbo Model ......................................................................................................................... 388
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9.4.8. Solution ............................................................................................................................... 390
9.4.9. Postprocessing ..................................................................................................................... 393
9.5. Summary ...................................................................................................................................... 396
9.6. Further Improvements .................................................................................................................. 396
10. Modeling Blade Row Interaction using Steady-State and Transient Simulations ............................ 397
10.1. Introduction ............................................................................................................................... 397
10.2. Prerequisites ............................................................................................................................... 397
10.3. Problem Description ................................................................................................................... 397
10.4. Setup and Solution ..................................................................................................................... 398
10.4.1. Preparation ........................................................................................................................ 399
10.4.2. Mesh .................................................................................................................................. 399
10.4.3. Solver Settings for the Steady State Mixing Plane Model ...................................................... 399
10.4.4. Models ............................................................................................................................... 400
10.4.5. Materials ............................................................................................................................ 401
10.4.6. Cell Zone Conditions for the Steady State Mixing Plane Model ............................................. 401
10.4.7. Operating Conditions ......................................................................................................... 402
10.4.8. Boundary Conditions for the Steady State Mixing Plane Model ............................................ 403
10.4.9. Solution of the Steady State Mixing Plane Model ................................................................. 413
10.4.10. Postprocessing of the Steady State Mixing Plane Model ..................................................... 421
10.4.11. Solver Settings for the Transient Pitch Scale Model ............................................................ 425
10.4.12. Reference Values .............................................................................................................. 426
10.4.13. Interface Conditions for the Transient Pitch Scale Model .................................................... 427
10.4.14. Cell Zone Conditions for the Transient Pitch Scale Model ................................................... 429
10.4.15. Boundary Conditions for the Transient Pitch Scale Model ................................................... 429
10.4.16. Solution settings for the Transient Pitch Scale Model ......................................................... 430
10.4.17. Postprocessing for the Transient Pitch Scale Model ............................................................ 435
10.5. Summary .................................................................................................................................... 440
11. Using Sliding Meshes ........................................................................................................................ 441
11.1. Introduction ............................................................................................................................... 441
11.2. Prerequisites ............................................................................................................................... 441
11.3. Problem Description ................................................................................................................... 442
11.4. Setup and Solution ..................................................................................................................... 442
11.4.1. Preparation ........................................................................................................................ 443
11.4.2. Mesh .................................................................................................................................. 443
11.4.3. General Settings ................................................................................................................. 443
11.4.4. Models ............................................................................................................................... 446
11.4.5. Materials ............................................................................................................................ 447
11.4.6. Cell Zone Conditions .......................................................................................................... 449
11.4.7. Boundary Conditions .......................................................................................................... 452
11.4.8. Operating Conditions ......................................................................................................... 458
11.4.9. Mesh Interfaces .................................................................................................................. 458
11.4.10. Solution ........................................................................................................................... 460
11.4.11. Postprocessing ................................................................................................................. 480
11.5. Summary .................................................................................................................................... 484
12. Using Overset and Dynamic Meshes ................................................................................................. 485
12.1. Prerequisites ............................................................................................................................... 485
12.2. Problem Description ................................................................................................................... 486
12.3. Preparation ................................................................................................................................. 487
12.4. Mesh .......................................................................................................................................... 487
12.5. Overset Interface Creation ........................................................................................................... 491
12.6. Steady-State Case Setup .............................................................................................................. 494
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12.6.1. General Settings ................................................................................................................. 494
12.6.2. Models ............................................................................................................................... 494
12.6.3. Materials ............................................................................................................................ 496
12.6.4. Operating Conditions ......................................................................................................... 496
12.6.5. Boundary Conditions .......................................................................................................... 496
12.6.6. Reference Values ................................................................................................................ 498
12.6.7. Solution ............................................................................................................................. 498
12.7. Unsteady Setup .......................................................................................................................... 504
12.7.1. General Settings ................................................................................................................. 504
12.7.2. Compile the UDF ................................................................................................................ 504
12.7.3. Dynamic Mesh Settings ...................................................................................................... 505
12.7.4. Report Generation for Unsteady Case ................................................................................. 507
12.7.5. Run Calculations for Unsteady Case .................................................................................... 509
12.7.6. Overset Solution Checking ................................................................................................. 510
12.7.7. Postprocessing ................................................................................................................... 510
12.7.8. Diagnosing an Overset Case ............................................................................................... 513
12.8. Summary .................................................................................................................................... 520
13. Modeling Species Transport and Gaseous Combustion ................................................................... 521
13.1. Introduction ............................................................................................................................... 521
13.2. Prerequisites ............................................................................................................................... 521
13.3. Problem Description ................................................................................................................... 522
13.4. Background ................................................................................................................................ 522
13.5. Setup and Solution ..................................................................................................................... 522
13.5.1. Preparation ........................................................................................................................ 523
13.5.2. Mesh .................................................................................................................................. 523
13.5.3. General Settings ................................................................................................................. 523
13.5.4. Models ............................................................................................................................... 526
13.5.5. Materials ............................................................................................................................ 529
13.5.6. Boundary Conditions .......................................................................................................... 532
13.5.7. Initial Reaction Solution ...................................................................................................... 538
13.5.8. Postprocessing ................................................................................................................... 542
13.5.9. NOx Prediction ................................................................................................................... 549
13.6. Summary .................................................................................................................................... 560
13.7. Further Improvements ................................................................................................................ 560
14. Using the Monte Carlo Radiation Model ........................................................................................... 563
14.1. Introduction ............................................................................................................................... 563
14.2. Prerequisites ............................................................................................................................... 563
14.3. Problem Description ................................................................................................................... 564
14.4. Setup and Solution ..................................................................................................................... 564
14.4.1. Preparation ........................................................................................................................ 565
14.4.2. Meshing Workflow .............................................................................................................. 565
14.4.3. Mesh .................................................................................................................................. 577
14.4.4. Models ............................................................................................................................... 579
14.4.5. Materials ............................................................................................................................ 581
14.4.6. Cell Zone Conditions .......................................................................................................... 583
14.4.7. Boundary Conditions .......................................................................................................... 584
14.4.8. Solution ............................................................................................................................. 586
14.4.9. Postprocessing ................................................................................................................... 588
14.5. Summary .................................................................................................................................... 592
14.6. Further Improvements ................................................................................................................ 592
15. Using the Eddy Dissipation and Steady Diffusion Flamelet Combustion Models ............................ 593
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15.1. Introduction ............................................................................................................................... 593
15.2. Prerequisites ............................................................................................................................... 593
15.3. Problem Description ................................................................................................................... 594
15.4. Setup and Solution ..................................................................................................................... 594
15.4.1. Preparation ........................................................................................................................ 595
15.4.2. Meshing Workflow .............................................................................................................. 595
15.4.3. Solver Settings ................................................................................................................... 603
15.4.4. Models ............................................................................................................................... 603
15.4.5. Boundary Conditions .......................................................................................................... 604
15.4.6. Solution ............................................................................................................................. 606
15.4.7. Postprocessing for the Eddy-Dissipation Solution ................................................................ 608
15.5. Steady Diffusion Flamelet Model Setup and Solution ................................................................... 614
15.5.1. Models ............................................................................................................................... 615
15.5.2. Boundary Conditions .......................................................................................................... 616
15.5.3. Solution ............................................................................................................................. 617
15.5.4. Postprocessing for the Steady Diffusion Flamelet Solution ................................................... 617
15.6. Summary .................................................................................................................................... 621
16. Modeling Surface Chemistry ............................................................................................................. 623
16.1. Introduction ............................................................................................................................... 623
16.2. Prerequisites ............................................................................................................................... 623
16.3. Problem Description ................................................................................................................... 624
16.4. Setup and Solution ..................................................................................................................... 625
16.4.1. Preparation ........................................................................................................................ 625
16.4.2. Reading and Checking the Mesh ......................................................................................... 625
16.4.3. Solver and Analysis Type ..................................................................................................... 627
16.4.4. Specifying the Models ........................................................................................................ 628
16.4.5. Defining Materials and Properties ....................................................................................... 630
16.4.6. Specifying Boundary Conditions ......................................................................................... 641
16.4.7. Setting the Operating Conditions ....................................................................................... 648
16.4.8. Simulating Non-Reacting Flow ............................................................................................ 649
16.4.9. Simulating Reacting Flow ................................................................................................... 651
16.4.10. Postprocessing the Solution Results .................................................................................. 657
16.5. Summary .................................................................................................................................... 664
17. Modeling Evaporating Liquid Spray ................................................................................................. 667
17.1. Introduction ............................................................................................................................... 667
17.2. Prerequisites ............................................................................................................................... 667
17.3. Problem Description ................................................................................................................... 667
17.4. Setup and Solution ..................................................................................................................... 668
17.4.1. Preparation ........................................................................................................................ 668
17.4.2. Mesh .................................................................................................................................. 669
17.4.3. Solver ................................................................................................................................. 672
17.4.4. Models ............................................................................................................................... 672
17.4.5. Materials ............................................................................................................................ 675
17.4.6. Boundary Conditions .......................................................................................................... 677
17.4.7. Initial Solution Without Droplets ......................................................................................... 683
17.4.8. Creating a Spray Injection ................................................................................................... 693
17.4.9. Solution ............................................................................................................................. 702
17.4.10. Postprocessing ................................................................................................................. 712
17.5. Summary .................................................................................................................................... 722
18. Using the VOF Model ......................................................................................................................... 723
18.1. Introduction ............................................................................................................................... 723
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18.2. Prerequisites ............................................................................................................................... 723
18.3. Problem Description ................................................................................................................... 723
18.4. Setup and Solution ..................................................................................................................... 725
18.4.1. Preparation ........................................................................................................................ 725
18.4.2. Reading and Manipulating the Mesh ................................................................................... 726
18.4.3. General Settings ................................................................................................................. 730
18.4.4. Models ............................................................................................................................... 733
18.4.5. Materials ............................................................................................................................ 734
18.4.6. Phases ................................................................................................................................ 736
18.4.7. Operating Conditions ......................................................................................................... 739
18.4.8. Boundary Conditions .......................................................................................................... 740
18.4.9. Solution ............................................................................................................................. 744
18.4.10. Postprocessing ................................................................................................................. 751
18.5. Summary .................................................................................................................................... 755
19. Modeling Cavitation .......................................................................................................................... 757
19.1. Introduction ............................................................................................................................... 757
19.2. Prerequisites ............................................................................................................................... 757
19.3. Problem Description ................................................................................................................... 757
19.4. Setup and Solution ..................................................................................................................... 758
19.4.1. Preparation ........................................................................................................................ 758
19.4.2. Reading and Checking the Mesh ......................................................................................... 759
19.4.3. Solver Settings ................................................................................................................... 760
19.4.4. Models ............................................................................................................................... 761
19.4.5. Materials ............................................................................................................................ 764
19.4.6. Phases ................................................................................................................................ 766
19.4.7. Boundary Conditions .......................................................................................................... 770
19.4.8. Operating Conditions ......................................................................................................... 775
19.4.9. Solution ............................................................................................................................. 775
19.4.10. Postprocessing ................................................................................................................. 780
19.5. Summary .................................................................................................................................... 785
20. Using the Eulerian Multiphase Model ............................................................................................... 787
20.1. Introduction ............................................................................................................................... 787
20.2. Prerequisites ............................................................................................................................... 787
20.3. Problem Description ................................................................................................................... 787
20.4. Setup and Solution ..................................................................................................................... 788
20.4.1. Preparation ........................................................................................................................ 789
20.4.2. Mesh .................................................................................................................................. 789
20.4.3. Solver Settings ................................................................................................................... 790
20.4.4. Models ............................................................................................................................... 791
20.4.5. Materials ............................................................................................................................ 792
20.4.6. Phases ................................................................................................................................ 793
20.4.7. Cell Zone Conditions .......................................................................................................... 794
20.4.8. Boundary Conditions .......................................................................................................... 795
20.4.9. Solution ............................................................................................................................. 795
20.4.10. Postprocessing ................................................................................................................. 797
20.5. Summary .................................................................................................................................... 803
21. Modeling Solidification ..................................................................................................................... 805
21.1. Introduction ............................................................................................................................... 805
21.2. Prerequisites ............................................................................................................................... 805
21.3. Problem Description ................................................................................................................... 805
21.4. Setup and Solution ..................................................................................................................... 806
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21.4.1. Preparation ........................................................................................................................ 807
21.4.2. Reading and Checking the Mesh ......................................................................................... 807
21.4.3. Specifying Solver and Analysis Type .................................................................................... 808
21.4.4. Specifying the Models ........................................................................................................ 810
21.4.5. Defining Materials .............................................................................................................. 811
21.4.6. Setting the Cell Zone Conditions ......................................................................................... 815
21.4.7. Setting the Boundary Conditions ........................................................................................ 815
21.4.8. Solution: Steady Conduction ............................................................................................... 824
21.4.9. Solution: Transient Flow and Heat Transfer ........................................................................... 835
21.5. Summary .................................................................................................................................... 846
22. Using the Eulerian Granular Multiphase Model with Heat Transfer ................................................. 847
22.1. Introduction ............................................................................................................................... 847
22.2. Prerequisites ............................................................................................................................... 847
22.3. Problem Description ................................................................................................................... 847
22.4. Setup and Solution ..................................................................................................................... 848
22.4.1. Preparation ........................................................................................................................ 849
22.4.2. Mesh .................................................................................................................................. 849
22.4.3. Solver Settings ................................................................................................................... 850
22.4.4. Models ............................................................................................................................... 851
22.4.5. UDF ................................................................................................................................... 852
22.4.6. Materials ............................................................................................................................ 853
22.4.7. Phases ................................................................................................................................ 854
22.4.8. Boundary Conditions .......................................................................................................... 858
22.4.9. Solution ............................................................................................................................. 866
22.4.10. Postprocessing ................................................................................................................. 879
22.5. Summary .................................................................................................................................... 882
22.6. References .................................................................................................................................. 882
23. Modeling One-Way Fluid-Structure Interaction (FSI) Within Fluent ................................................. 883
23.1. Introduction ............................................................................................................................... 883
23.2. Prerequisites ............................................................................................................................... 883
23.3. Problem Description ................................................................................................................... 884
23.4. Setup and Solution ..................................................................................................................... 884
23.4.1. Preparation ........................................................................................................................ 884
23.4.2. Structural Model ................................................................................................................. 886
23.4.3. Materials ............................................................................................................................ 887
23.4.4. Cell Zone Conditions .......................................................................................................... 889
23.4.5. Boundary Conditions .......................................................................................................... 890
23.4.6. Solution ............................................................................................................................. 893
23.4.7. Postprocessing ................................................................................................................... 896
23.5. Summary .................................................................................................................................... 897
24. Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent ................................................. 899
24.1. Introduction ............................................................................................................................... 899
24.2. Prerequisites ............................................................................................................................... 899
24.3. Problem Description ................................................................................................................... 900
24.4. Setup and Solution ..................................................................................................................... 900
24.4.1. Preparation ........................................................................................................................ 900
24.4.2. Solver and Analysis Type ..................................................................................................... 903
24.4.3. Structural Model ................................................................................................................. 904
24.4.4. Materials ............................................................................................................................ 905
24.4.5. Cell Zone Conditions .......................................................................................................... 906
24.4.6. Boundary Conditions .......................................................................................................... 907
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24.4.7. Dynamic Mesh Zones ......................................................................................................... 910
24.4.8. Solution Animations ........................................................................................................... 914
24.4.9. Solution ............................................................................................................................. 925
24.4.10. Postprocessing ................................................................................................................. 928
24.5. Summary .................................................................................................................................... 932
25. Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder ............................................................ 933
25.1. Introduction ............................................................................................................................... 933
25.2. Problem Description ................................................................................................................... 933
25.3. Setup and Solution ..................................................................................................................... 934
25.3.1. Step 1: Preparation ............................................................................................................. 934
25.3.2. Step 2: Define Observables ................................................................................................. 935
25.3.3. Step 3: Compute the Drag Sensitivity .................................................................................. 939
25.3.4. Step 4: Postprocess and Export Drag Sensitivity ................................................................... 943
25.3.4.1. Boundary Condition Sensitivity .................................................................................. 943
25.3.4.2. Momentum Source Sensitivity ................................................................................... 944
25.3.4.3. Shape Sensitivity ....................................................................................................... 946
25.3.4.4. Exporting Drag Sensitivity Data .................................................................................. 948
25.3.5. Step 5: Compute Lift Sensitivity ........................................................................................... 951
25.3.6. Step 6: Modify the Shape .................................................................................................... 952
25.4. Summary .................................................................................................................................... 959
26. Simulating a Single Battery Cell Using the MSMD Battery Model .................................................... 961
26.1. Introduction ............................................................................................................................... 961
26.2. Prerequisites ............................................................................................................................... 961
26.3. Problem Description ................................................................................................................... 961
26.4. Setup and Solution ..................................................................................................................... 962
26.4.1. Preparation ........................................................................................................................ 962
26.4.2. Reading and Scaling the Mesh ............................................................................................ 963
26.4.3. NTGK Battery Model Setup ................................................................................................. 963
26.4.3.1. Specifying Solver and Models ..................................................................................... 963
26.4.3.2. Defining New Materials for Cell and Tabs .................................................................... 967
26.4.3.3. Defining Cell Zone Conditions .................................................................................... 971
26.4.3.4. Defining Boundary Conditions ................................................................................... 971
26.4.3.5. Specifying Solution Settings ....................................................................................... 972
26.4.3.6. Obtaining Solution .................................................................................................... 976
26.4.4. Postprocessing ................................................................................................................... 978
26.4.5. Simulating the Battery Pulse Discharge Using the ECM Model ............................................. 991
26.4.6. Using the Reduced Order Method (ROM) ............................................................................ 992
26.4.7. External and Internal Short-Circuit Treatment ...................................................................... 993
26.4.7.1. Setting up and Solving a Short-Circuit Problem .......................................................... 993
26.4.7.2. Postprocessing .......................................................................................................... 995
26.5. Summary .................................................................................................................................. 1000
26.6. Appendix .................................................................................................................................. 1000
26.7. References ................................................................................................................................ 1002
27. Simulating a 1P3S Battery Pack Using the Battery Model .............................................................. 1003
27.1. Introduction .............................................................................................................................. 1003
27.2. Prerequisites ............................................................................................................................. 1003
27.3. Problem Description ................................................................................................................. 1003
27.4. Setup and Solution .................................................................................................................... 1004
27.4.1. Preparation ...................................................................................................................... 1004
27.4.2. Reading and Scaling the Mesh .......................................................................................... 1005
27.4.3. Battery Model Setup ......................................................................................................... 1006
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27.4.3.1. Specifying Solver and Models ................................................................................... 1006
27.4.3.2. Defining New Materials ............................................................................................ 1011
27.4.3.3. Defining Cell Zone Conditions .................................................................................. 1014
27.4.3.4. Defining Boundary Conditions ................................................................................. 1015
27.4.3.5. Specifying Solution Settings ..................................................................................... 1016
27.4.3.6. Obtaining Solution .................................................................................................. 1020
27.4.4. Postprocessing ................................................................................................................. 1022
27.5. Summary .................................................................................................................................. 1031
28. In-Flight Icing Tutorial Using Fluent Icing ....................................................................................... 1033
28.1. Fluent Airflow on the Clean NACA0012 Airfoil ........................................................................... 1033
28.1.1. Setting up a Fluent Airflow Simulation on a Clean NACA0012 Airfoil .................................. 1034
28.1.2. Conducting a Fluent Airflow Simulation on Clean NACA0012 Airfoil ................................... 1037
28.2. Fluent Airflow on the Rough NACA0012 Airfoil ........................................................................... 1042
28.3. Droplet Impingement on the NACA0012 ................................................................................... 1046
28.3.1. Monodispersed Calculation .............................................................................................. 1047
28.3.2. Langmuir-D Distribution ................................................................................................... 1052
28.3.3. Post-Processing Using Viewmerical ................................................................................... 1056
28.4. Fluent Icing Ice Accretion on the NACA0012 .............................................................................. 1065
28.5. Postprocessing an Ice Accretion Solution Using CFD-Post Macros ............................................... 1072
28.6. Multi-Shot Ice Accretion with Automatic Mesh Displacement ..................................................... 1079
28.7. Multi-Shot Ice Accretion with Automatic Mesh Displacement – Postprocessing Using CFD-Post ... 1084
28.8. FENSAP Airflow on the Clean NACA0012 Airfoil .......................................................................... 1089
28.8.1. FENSAP Airflow Solution on a Clean NACA0012 Airfoil ....................................................... 1089
28.9. FENSAP Airflow Solution on the Rough NACA0012 Airfoil ........................................................... 1093
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List of Figures
1.1. Manifold Geometry for Flow Modeling .................................................................................................... 2
1.2. Mass Flow Rate History ......................................................................................................................... 30
1.3. Residuals .............................................................................................................................................. 30
1.4. Pathlines Through the Manifold ............................................................................................................. 32
1.5. Scene Containing the Mesh and Pathlines Throughout the Manifold ...................................................... 36
1.6. Contours of Velocity Magnitude at the Outlet ........................................................................................ 39
1.7. Contours of Temperature at the mid-plane ............................................................................................ 42
1.8. Contours of Temperature on the Exhaust Manifold ................................................................................. 44
2.1. Manifold Geometry for Flow Modeling .................................................................................................. 46
2.2. Mesh Display of the Exhaust Manifold ................................................................................................... 49
2.3. Graphics Window with Default Lighting ................................................................................................ 51
2.4. Display with Additional Lighting: - Headlight Off .................................................................................... 52
2.5. Display with Additional Lighting ........................................................................................................... 53
2.6. Filled Contours of Temperature on the Mid-Plane-x and the Outlet ......................................................... 59
2.7. Filled Contours of Temperature for the Surface of the Manifold .............................................................. 60
2.8. Velocity Vectors in the Mid-Plane of the Manifold ................................................................................... 62
2.9. Velocity Vectors mid-plane in the z-direction ......................................................................................... 64
2.10. Filled Temperature Contours on the mid-plane-x, clip-z-inner and outlet-plane Surfaces ....................... 66
2.11. Filled Temperature Contours on the Mid-Plane, Inner-Clip, and Outlet-Plane Surfaces ........................... 68
2.12. Temperature Contours and Velocity Vectors Scene ............................................................................... 71
2.13. Exploded Scene Display of Temperature, Velocity, and Pathlines ........................................................... 74
2.14. Temperature Along a Solid Portion of the Manifold .............................................................................. 80
2.15. A Display with Annotation ................................................................................................................... 81
3.1. Catalytic Converter Geometry for Flow Modeling ................................................................................... 86
3.2. The Imported CAD Geometry for the Catalytic Converter ....................................................................... 90
3.3. Mesh for the Catalytic Converter Geometry in Fluent (Solver Mode) ..................................................... 105
3.4. Mass Flow Rate History ........................................................................................................................ 119
3.5. Velocity Vectors Through the Interior ................................................................................................... 127
3.6. Contours of Static Pressure Through the Interior .................................................................................. 129
3.7. Contours of Velocity Magnitude on the z=185, z=230, z=280, z=330, and z=375 Surfaces ...................... 131
4.1. Problem Specification ......................................................................................................................... 135
4.2. The Imported CAD Geometry for the Wing .......................................................................................... 139
4.3. The Entire Mesh .................................................................................................................................. 150
4.4. Magnified View of the Mesh Around the Wing ..................................................................................... 151
4.5. Contour Plot of y+ Distribution ............................................................................................................ 165
4.6. Contour Plot of Pressure ...................................................................................................................... 167
4.7. Improved Contour Plot of Pressure ...................................................................................................... 169
4.8. Contour Plot of Mach Number ............................................................................................................. 171
4.9. Contour Plot of x Component of Velocity ............................................................................................. 173
4.10. Plot of Velocity Vectors Downstream of the Shock .............................................................................. 175
4.11. XY Plot of x Wall Shear Stress ............................................................................................................. 177
5.1. Problem Specification ......................................................................................................................... 181
5.2. Convergence History of the Mass-Weighted Average Temperature ....................................................... 217
5.3. Residuals ............................................................................................................................................ 218
5.4. Predicted Velocity Distribution after the Initial Calculation ................................................................... 222
5.5. Predicted Temperature Distribution after the Initial Calculation ............................................................ 224
5.6. Velocity Vectors Colored by Velocity Magnitude ................................................................................... 226
5.7. Resized Velocity Vectors ...................................................................................................................... 227
5.8. Magnified View of Resized Velocity Vectors .......................................................................................... 228
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5.9. Outlet Temperature Profile for the Initial Solution ................................................................................ 231
5.10. Contours of the Dynamic Head Custom Field Function ....................................................................... 233
5.11. Cells Marked for Adaption ................................................................................................................. 237
5.12. Alternative Display of Cells Marked for Adaption ................................................................................ 239
5.13. The Adapted Mesh ............................................................................................................................ 241
5.14. The Complete Residual History .......................................................................................................... 242
5.15. Convergence History of Mass-Weighted Average Temperature ........................................................... 242
5.16. Filled Contours of Temperature Using the Adapted Mesh ................................................................... 243
5.17. Outlet Temperature Profile for the Adapted Coupled Solver Solution .................................................. 244
5.18. Outlet Temperature Profiles for the Two Solutions .............................................................................. 247
6.1. Exhaust System Geometry for Flow Modeling ...................................................................................... 250
6.2. Manifold CAD Geometry for Flow Modeling ......................................................................................... 253
6.3. Residuals ............................................................................................................................................ 283
6.4. Mass Balance History ........................................................................................................................... 283
6.5. Pathlines Through the Manifold ........................................................................................................... 285
6.6. Contours of Velocity Magnitude Through the Manifold ........................................................................ 287
6.7. Scene Containing the Mesh and Contours Throughout the Manifold .................................................... 290
7.1. Problem Specification ......................................................................................................................... 292
7.2. The Imported CAD Geometry for the Capsule ...................................................................................... 295
7.3. View of the Mesh Around the Capsule ................................................................................................. 307
8.1. Problem Specification ......................................................................................................................... 336
8.2. 2D Nozzle Mesh Display with Mirroring ............................................................................................... 339
8.3. Mass Flow Rate History ........................................................................................................................ 357
8.4. 2D Nozzle Mesh after Adaption ........................................................................................................... 359
8.5. Contours of Static Pressure (Steady Flow) ............................................................................................. 361
8.6. Velocity Vectors Showing Recirculation (Steady Flow) .......................................................................... 363
8.7. Mass Flow Rate History (Transient Flow) .............................................................................................. 369
8.8. Pressure Contours at t=0.017136 s ....................................................................................................... 373
8.9. Mach Number Contours at t=0.017136 s .............................................................................................. 375
8.10. Pressure Contours at t=0.017993 s ..................................................................................................... 378
8.11. Pressure Contours at t=0.019135 s ..................................................................................................... 378
8.12. Mach Number Contours at t=0.017993 s ............................................................................................ 379
8.13. Mach Number Contours at t=0.019135 s ............................................................................................ 379
8.14. Velocity Vectors at t=0.018849 s ......................................................................................................... 382
9.1. Case Geometry ................................................................................................................................... 384
9.2. Convergence History of the Pump Head ............................................................................................. 393
9.3. Contours of Velocity Magnitude at the Outlet ...................................................................................... 394
9.4. Contours of Static Pressure on the Walls ............................................................................................... 395
9.5. Contours of Static Pressure .................................................................................................................. 396
10.1. Case Geometry ................................................................................................................................. 398
10.2. Pressure Ratio ................................................................................................................................... 420
10.3. Outlet Mass Flow Rate ....................................................................................................................... 420
10.4. Efficiency .......................................................................................................................................... 421
10.5. Contours of Velocity Magnitiue .......................................................................................................... 423
10.6. Contours of Static Pressure ................................................................................................................ 424
10.7. Contours of Static Temperature ......................................................................................................... 425
10.8. Pressure Ratio ................................................................................................................................... 434
10.9. Outlet Mass Flow Rate ....................................................................................................................... 434
10.10. Efficiency ........................................................................................................................................ 435
10.11. Contours of Entropy ........................................................................................................................ 436
10.12. Contours of Velocity Magnitiue ........................................................................................................ 438
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10.13. Contours of Static Pressure .............................................................................................................. 439
10.14. Contours of Static Temperature ....................................................................................................... 440
11.1. Rotor-Stator Problem Description ...................................................................................................... 442
11.2. Rotor-Stator Display .......................................................................................................................... 444
11.3. Residual History for the First Revolution of the Rotor .......................................................................... 470
11.4. Mass Flow Rate at the Inlet During the First Revolution ...................................................................... 471
11.5. Mass Flow Rate at the Outlet During the First Revolution .................................................................... 471
11.6. Static Pressure at the Interface During the First Revolution ................................................................. 472
11.7. Mass Flow Rate at the Inlet During the Next 3 Revolutions ................................................................. 475
11.8. Mass Flow Rate at the Outlet During the Next 3 Revolutions ............................................................... 475
11.9. Static Pressure at the Interface During the Next 3 Revolutions ............................................................ 476
11.10. Static Pressure at a Point on The Stator Interface During the Final Revolution .................................... 480
11.11. FFT of Static Pressure at the Stator ................................................................................................... 482
11.12. Mean Static Pressure on the Outer Shroud of the Axial Compressor .................................................. 484
12.1. Schematic of Problem ....................................................................................................................... 486
12.2. Close View of Bay Area ...................................................................................................................... 487
12.3. Cell Marking on component .............................................................................................................. 517
12.4. Cell Marking on fluid-background ..................................................................................................... 518
12.5. Dead Cells in the Component ............................................................................................................ 519
12.6. Dead Cells in the Background ............................................................................................................ 520
13.1. Combustion of Methane Gas in a Turbulent Diffusion Flame Furnace .................................................. 522
13.2. The Quadrilateral Mesh for the Combustor Model .............................................................................. 525
13.3. Contours of Temperature ................................................................................................................... 543
13.4. Velocity Vectors ................................................................................................................................. 545
13.5. Contours of CH4 Mass Fraction .......................................................................................................... 546
13.6. Contours of O2 Mass Fraction ............................................................................................................ 546
13.7. Contours of CO2 Mass Fraction .......................................................................................................... 547
13.8. Contours of H2O Mass Fraction .......................................................................................................... 547
13.9. Contours of NO Mass Fraction — Prompt and Thermal NOx Formation ............................................... 555
13.10. Contours of NO Mass Fraction—Thermal NOx Formation ................................................................. 556
13.11. Contours of NO Mass Fraction—Prompt NOx Formation .................................................................. 558
13.12. Contours of NO ppm — Prompt NOx Formation ............................................................................... 560
14.1. Case Geometry ................................................................................................................................. 564
14.2. The Imported CAD Geometry for the Headlamp ................................................................................. 567
14.3. Graphics Display of Headlamp Mesh .................................................................................................. 579
14.4. Contour of Temperature on Inner Bezel .............................................................................................. 590
14.5. Contour of Radiation Intensity Normalized Standard Deviation on Inner Bezel .................................... 592
15.1. Can Combustor Geometry ................................................................................................................. 594
15.2. Scaled Residuals ................................................................................................................................ 607
15.3. Convergence History of Mass-Weighted Average CO2 on the Outlet ................................................... 608
15.4. Contours of CO2 Mass Fraction .......................................................................................................... 612
15.5. Contours of O2 Mass Fraction ............................................................................................................ 613
15.6. Contours of Static Temperature on the Combustor Walls .................................................................... 614
15.7. Contours of Mean Mixture Fraction .................................................................................................... 618
15.8. Contours of CO2 Mass Fraction .......................................................................................................... 619
15.9. Convergence History of Mass-Weighted Average CO2 on the Outlet ................................................... 621
16.1. Schematic of the Reactor Configuration ............................................................................................. 624
16.2. Mesh Display .................................................................................................................................... 627
16.3. Contours of Surface Deposition Rate of Ga ......................................................................................... 655
16.4. Scaled Residuals ................................................................................................................................ 656
16.5. Temperature Contours Near wall-4 .................................................................................................... 660
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16.6. Contours of Surface Deposition Rate of ga ......................................................................................... 660
16.7. Contours of Surface Coverage of ga_s ................................................................................................ 662
16.8. Plot of Surface Deposition Rate of Ga ................................................................................................. 664
17.1. Problem Specification ....................................................................................................................... 668
17.2. Air-Blast Atomizer Mesh Display ........................................................................................................ 672
17.3. Scaled Residuals ................................................................................................................................ 687
17.4. Velocity Magnitude at Mid-Point of Atomizer Section ......................................................................... 690
17.5. Pathlines of Air in the Swirling Annular Stream ................................................................................... 693
17.6. Convergence History of Mass Fraction of ch3oh on Fluid .................................................................... 710
17.7. Convergence History of DPM Mass Source on Fluid ............................................................................ 710
17.8. Convergence History of Total Mass in Domain .................................................................................... 711
17.9. Convergence History of Evaporated Particle Mass .............................................................................. 711
17.10. Particle Tracks for the Spray Injection ............................................................................................... 713
17.11. Contours of DPM Temperature ......................................................................................................... 715
17.12. Contours of DPM Sauter Diameter ................................................................................................... 716
17.13. Vectors of DPM Mean Velocity Colored by DPM Velocity Magnitude .................................................. 718
17.14. Full Atomizer Display with Surface of Constant Methanol Mass Fraction ........................................... 721
17.15. Atomizer Display with Surface of Constant Methanol Mass Fraction Enhanced .................................. 722
18.1. Schematic of the Problem ................................................................................................................. 724
18.2. Default Display of the Nozzle Mesh .................................................................................................... 726
18.3. The Quadrilateral Mesh ..................................................................................................................... 727
18.4. Mesh Display of the Nozzle Mirrored and Upright .............................................................................. 730
18.5. Contours of Water Volume Fraction After 6 μs .................................................................................... 753
18.6. Contours of Water Volume Fraction After 12 μs ................................................................................... 754
18.7. Contours of Water Volume Fraction After 18 μs ................................................................................... 754
18.8. Contours of Water Volume Fraction After 24 μs ................................................................................... 755
18.9. Contours of Water Volume Fraction After 30 μs ................................................................................... 755
19.1. Problem Schematic ........................................................................................................................... 758
19.2. The Mesh in the Orifice ...................................................................................................................... 760
19.3. Contours of Static Pressure ................................................................................................................ 782
19.4. Mirrored View of Contours of Static Pressure ...................................................................................... 783
19.5. Contours of Turbulent Kinetic Energy ................................................................................................. 784
19.6. Contours of Vapor Volume Fraction .................................................................................................... 785
20.1. Problem Schematic ........................................................................................................................... 788
20.2. Mesh Display of the Mixing Tank ........................................................................................................ 790
20.3. Residual History ................................................................................................................................ 797
20.4. Contours of Air Volume Fraction on the XZ plane ............................................................................... 799
20.5. Contours of Air Volume Fraction on the z=0.08 plane ......................................................................... 800
20.6. Vectors of Water Velocity Magnitude on the XZ plane ......................................................................... 801
20.7. Vectors of Air Velocity Magnitude on the XZ plane ............................................................................. 802
21.1. Solidification in Czochralski Model .................................................................................................... 806
21.2. Mesh Display .................................................................................................................................... 808
21.3. Contours of Temperature for the Steady Conduction Solution ............................................................ 833
21.4. Contours of Temperature (Mushy Zone) for the Steady Conduction Solution ...................................... 835
21.5. Contours of Temperature at t=0.2 s .................................................................................................... 841
21.6. Contours of Stream Function at t=0.2 s .............................................................................................. 842
21.7. Contours of Liquid Fraction at t=0.2 s ................................................................................................. 843
21.8. Contours of Temperature at t=5 s ....................................................................................................... 844
21.9. Contours of Stream Function at t=5 s ................................................................................................. 845
21.10. Contours of Liquid Fraction at t=5 s ................................................................................................. 846
22.1. Problem Schematic ........................................................................................................................... 848
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22.2. Mesh Display of the Fluidized Bed ..................................................................................................... 850
22.3. Initial Volume Fraction of Granular Phase (solids) ............................................................................... 877
22.4. Plot of Mixture-Averaged Heat Transfer Coefficient in the Cell Next to the Heated Wall Versus Time ..... 879
22.5. Contours of Static Pressure ................................................................................................................ 881
22.6. Contours of Volume Fraction of Solids ................................................................................................ 882
23.1. Problem Schematic ........................................................................................................................... 884
23.2. Velocity Magnitude on the Symmetry Plane ....................................................................................... 886
23.3. Contours of Total Displacement ......................................................................................................... 897
24.1. Problem Schematic ........................................................................................................................... 900
24.2. Steady-State Velocity Magnitude ....................................................................................................... 902
24.3. Duct with Mirroring .......................................................................................................................... 903
24.4.The Vertex Average Displacement of the Flap's Point Surface .............................................................. 928
24.5. Contours of Velocity Magnitude ........................................................................................................ 930
24.6. Contours of Total Displacement ......................................................................................................... 931
24.7. The Mesh of the Displaced Flap ......................................................................................................... 932
25.1. Mesh Close to the Cylinder Surface .................................................................................................... 935
25.2. Contours of Velocity Magnitude ........................................................................................................ 935
25.3. Adjoint Observables Dialog Box ........................................................................................................ 936
25.4. Manage Adjoint Observables Dialog Box ........................................................................................... 936
25.5. Create New Observable Dialog Box .................................................................................................... 937
25.6. Manage Observables Dialog Box ....................................................................................................... 938
25.7. Adjoint Observables Dialog Box ........................................................................................................ 939
25.8. Adjoint Solution Controls Dialog Box ................................................................................................. 940
25.9. Adjoint Residual Monitors Dialog Box ................................................................................................ 942
25.10. Run Adjoint Calculation Dialog Box .................................................................................................. 942
25.11. Residuals for the Converged Solution .............................................................................................. 943
25.12. Adjoint Reporting Dialog Box .......................................................................................................... 944
25.13. Contours Dialog Box When Plotting Adjoint Fields ........................................................................... 945
25.14. Adjoint Sensitivity to Body Force X-Component Contours ................................................................ 946
25.15. Vectors Dialog Box .......................................................................................................................... 947
25.16. Shape Sensitivity Colored by Sensitivity to Mass Sources (Cell Values) ............................................... 948
25.17. The Design Tool Dialog Box ............................................................................................................. 949
25.18. Morphing Region Around Cylinder .................................................................................................. 950
25.19. The Design Tool Dialog Box Objectives Tab ...................................................................................... 951
25.20. Morphing Preview of Cylinder ......................................................................................................... 957
25.21. Mesh After Deformation .................................................................................................................. 958
26.1. Schematic of the Battery Cell Problem ............................................................................................... 962
26.2. Model Options .................................................................................................................................. 964
26.3. Conductive Zones ............................................................................................................................. 965
26.4. Electric Contacts ............................................................................................................................... 966
26.5. Residual History of the Simulation ..................................................................................................... 977
26.6. Report Plot of Discharge Curve at 1 C ................................................................................................ 977
26.7. History of Maximum Temperature in the Domain ............................................................................... 978
26.8. Contour Plot of Phase Potential for the Positive Electrode .................................................................. 980
26.9. Contour Plot of Phase Potential for the Negative Electrode ................................................................. 982
26.10. Contour Plot of Phase Potential for Passive Zones ............................................................................. 984
26.11. Contour Plot of Temperature ........................................................................................................... 986
26.12. Vector Plot of Current Density .......................................................................................................... 988
26.13. NTGK Model: Discharge Curves ........................................................................................................ 990
26.14. NTGK Model: Maximum Temperature in the Domain ........................................................................ 990
26.15. Battery Pulse Discharge ................................................................................................................... 992
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26.16. Internal Short Circuit Region Marked for Patching ............................................................................ 993
26.17. The Vector Plots of Current at the Positive Current Collectors ............................................................ 997
26.18. The Vector Plots of Current at the Negative Current Collectors .......................................................... 998
26.19. Contour Plot of Temperature ........................................................................................................... 999
27.1. Schematic of the Battery Pack Problem ............................................................................................ 1004
27.2. Model Options ................................................................................................................................ 1007
27.3. Conductive Zones ........................................................................................................................... 1009
27.4. Electric Contacts ............................................................................................................................. 1010
27.5. Residual History of the Simulation ................................................................................................... 1021
27.6. Surface Report Plot of Discharge Curve at 200W .............................................................................. 1021
27.7. Volume Report Plot of Maximum Temperature in the Domain .......................................................... 1022
27.8. Vector Plot of Current Density .......................................................................................................... 1025
27.9. Contour Plot of Temperature ........................................................................................................... 1027
27.10. Ohmic Heat Generation Rate ......................................................................................................... 1029
27.11. Total Heat Generation Rate ............................................................................................................ 1031
28.1. NACA0012 Structured C-Mesh Overview and Close-Up .................................................................... 1034
28.2. Scaled Residuals .............................................................................................................................. 1039
28.3. Convergence of Lift and Drag Coefficients of the Clean Airfoil .......................................................... 1040
28.4. The Residual Values ......................................................................................................................... 1040
28.5. Convective Heat Flux over the Clean NACA0012 Airfoil ..................................................................... 1041
28.6. Scaled Residuals .............................................................................................................................. 1044
28.7. Convergence of Lift and Drag Coefficients of the Rough Airfoil ......................................................... 1045
28.8. The Residual Values ......................................................................................................................... 1046
28.9. Convective Heat Flux Over the Rough NACA0012 Airfoil ................................................................... 1046
28.10. Convergence of Residuals: Momentum, LWC and Average Residuals ............................................... 1049
28.11. Convergence of Total Beta and Change in Total Beta Curves ........................................................... 1050
28.12. Collection Efficiency of Monodispersed Droplets over a NACA0012 ................................................ 1051
28.13. LWC of Monodispersed Droplets Around a NACA0012 .................................................................... 1052
28.14. Collection Efficiency of Droplets with Langmuir-D Distribution over a NACA0012 ........................... 1054
28.15. LWC of Droplets with Langmuir-D Distribution Around a NACA0012 ............................................... 1055
28.16. LWC of a Langmuir D Droplet Cloud over a NACA0012 at an AoA of 4 Degrees, Showing the Shadow
Zone (Blue Region) ................................................................................................................................. 1058
28.17. Collection Efficiency of a Langmuir D Droplet Cloud on the Surface of the Airfoil at an AoA of 4 Degrees ...................................................................................................................................................... 1058
28.18. Collection Efficiency of a Langmuir D Droplet Cloud on the Surface of the Airfoil at an AoA of 4 Degrees ...................................................................................................................................................... 1060
28.19. Collection Efficiency on the Surface of the Airfoil at an AoA of 4 Degrees, Langmuir D Droplet Solutions ....................................................................................................................................................... 1062
28.20. Collection Efficiency on the Surface, Langmuir D vs. Monodisperse ................................................. 1064
28.21. LWC Distribution and Shadow Zones for 44.4 Micron Droplets (Left) and 6.2 Micron Droplets
(Right) .................................................................................................................................................... 1065
28.22. Mass Conservation Table Printed in the Log File of Fluent Icing ....................................................... 1067
28.23. Ice View in Viewmerical Showing Shaded + Wireframe, -25 °C ......................................................... 1068
28.24. Ice View in Viewmerical Showing Metallic + Smooth, , -7.5 °C .......................................................... 1069
28.25. Ice Shapes at -25, -10, and -7.5 C ..................................................................................................... 1070
28.26. Film Height Variation over the Ice at -25, -10, and -7.5 C .................................................................. 1072
28.27. Ice View with CFD-Post, Ice Cover ................................................................................................... 1075
28.28. Ice View in CFD-Post, Ice Cover with Display Mesh .......................................................................... 1076
28.29. Ice View in CFD-Post, Instantaneous Ice Growth over Ice Cover Surface ........................................... 1077
28.30. 2D-Plot in CFD-Post, Clean Wall Surface and Ice Cover Surface ........................................................ 1078
28.31. 2D-Plot in CFD-Post, Water Film Distribution ................................................................................... 1079
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28.32. 3-Shots Ice Shape at -7.5 C ............................................................................................................. 1082
28.33. Ice Shapes at -7.5 C, Obtained Using One Shot and Three Shots Computations ................................ 1083
28.34. Ice View in CFD-Post, Final Ice Shape .............................................................................................. 1085
28.35. Ice View in CFD-Post, Instantaneous Ice Growth over Ice Cover Surface, Final Ice Shape ................... 1086
28.36. 2D-Plot in CFD-Post, Ice Shapes of the Multishot Simulation ........................................................... 1088
28.37. NACA0012 Structured C-Mesh Overview and Close-Up .................................................................. 1089
28.38. Scaled Residuals ............................................................................................................................ 1091
28.39. Convergence of Lift and Drag Coefficients of the Rough Airfoil ....................................................... 1092
28.40. The Residual Values ....................................................................................................................... 1093
28.41. Convective Heat Flux over the Clean NACA0012 Airfoil ................................................................... 1093
28.42. Scaled Residuals ............................................................................................................................ 1095
28.43. Convergence of Lift and Drag Coefficients of the Rough Airfoil ....................................................... 1096
28.44. The Residual Values ....................................................................................................................... 1097
28.45. Convective Heat Flux over the NACA0012 ...................................................................................... 1097
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List of Tables
1. Mini Flow Chart Symbol Descriptions ..................................................................................................... xxiv
3.1. Values for the Principle Direction Vectors ............................................................................................. 111
3.2. Values for the Viscous and Inertial Resistance ....................................................................................... 112
12.1. Meaning of Values ............................................................................................................................. 515
16.1. Selected Species ............................................................................................................................... 632
16.2. Selected Site and Solid Species .......................................................................................................... 635
16.3. Reaction Parameters ......................................................................................................................... 636
16.4. Properties of Species ......................................................................................................................... 639
16.5. Properties of Species ......................................................................................................................... 640
18.1. Ink Chamber Dimensions .................................................................................................................. 724
28.1. Simulation Flight Conditions ........................................................................................................... 1035
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Using This Manual
This preface is divided into the following sections:
1. What’s In This Manual
2. How To Use This Manual
3.Typographical Conventions Used In This Manual
1. What’s In This Manual
The ANSYS Fluent Tutorial Guide contains a number of tutorials that teach you how to use ANSYS Fluent to solve different types of problems. In each tutorial, features related to problem setup and postprocessing are demonstrated.
2. How To Use This Manual
Depending on your familiarity with computational fluid dynamics and the ANSYS Fluent software, you
can use this tutorial guide in a variety of ways.
2.1. For the Beginner
If you are a beginning user of ANSYS Fluent you should first read and solve Tutorial 1, in order to familiarize yourself with the interface and with basic setup and solution procedures. You may then
want to try a tutorial that demonstrates features that you are going to use in your application.
You may want to refer to other tutorials for instructions on using specific features, such as custom
field functions, mesh scaling, and so on, even if the problem solved in the tutorial is not of particular
interest to you.
2.2. For the Experienced User
If you are an experienced ANSYS Fluent user, you can read and/or solve the tutorial(s) that demonstrate
features that you are going to use in your application.
You may want to refer to other tutorials for instructions on using specific features, such as custom
field functions, mesh scaling, and so on, even if the problem solved in the tutorial is not of particular
interest to you.
3. Typographical Conventions Used In This Manual
Several typographical conventions are used in this manual’s text to help you find commands in the
user interface.
• Different type styles are used to indicate graphical user interface items and text interface items. For
example:
Iso-Surface dialog box
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Using This Manual
surface/iso-surface text command
• The text interface type style is also used when illustrating exactly what appears on the screen to
distinguish it from the narrative text. In this context, user inputs are typically shown in boldface. For
example,
solve/initialize/set-fmg-initialization
Customize your FMG initialization:
set the number of multigrid levels [5]
set FMG parameters on levels ..
residual reduction on level 1 is: [0.001]
number of cycles on level 1 is: [10] 100
residual reduction on level 2 is: [0.001]
number of cycles on level 2 is: [50] 100
• Mini flow charts are used to guide you through the ribbon or the tree, leading you to a specific option,
dialog box, or task page. The following tables list the meaning of each symbol in the mini flow charts.
Table 1: Mini Flow Chart Symbol Descriptions
Symbol
Indicated Action
Look at the ribbon
Look at the tree
Double-click to open task page
Select from task page
Right-click the preceding item
For example,
Setting Up Domain → Mesh → Transform → Translate...
indicates selecting the Setting Up Domain ribbon tab, clicking Transform (in the Mesh group box)
and selecting Translate..., as indicated in the figure below:
And
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Typographical Conventions Used In This Manual
Setup → Models → Viscous
Model → Realizable k-epsilon
indicates expanding the Setup and Models branches, right-clicking Viscous, and selecting Realizable
k-epsilon from the Model sub-menu, as shown in the following figure:
And
Setup →
Boundary Conditions →
velocity-inlet-5
indicates opening the task page as shown below:
In this manual, mini flow charts usually accompany a description of a dialog box or command, or a
screen illustration showing how to use the dialog box or command. They show you how to quickly
access a command or dialog box without having to search the surrounding material.
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• In-text references to File ribbon tab selections can be indicated using a "/". For example
File/Write/Case... indicates clicking the File ribbon tab and selecting Case... from the Write submenu
(which opens the Select File dialog box).
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Chapter 1: Fluid Flow in an Exhaust Manifold
This tutorial is divided into the following sections:
1.1. Introduction
1.2. Prerequisites
1.3. Problem Description
1.4. Setup and Solution
1.5. Postprocessing
1.6. Summary
1.1. Introduction
Licensing Capability:
This tutorial is fully supported at all licensing levels.
This tutorial illustrates the setup and solution of a three-dimensional turbulent fluid flow and heat
transfer problem in a manifold. The manifold configuration is encountered in the automotive industry.
It is often important to predict the flow field and temperature field in the area of the mixing region in
order to properly design the junction.
This tutorial demonstrates how to do the following in ANSYS Fluent:
• Use the Watertight Geometry guided workflow to:
– Import a CAD geometry
– Generate a surface mesh
– Cap inlets and outlets
– Extract a fluid region
– Generate a volume mesh
• Set up appropriate physics and boundary conditions.
• Calculate a solution.
• Review the results of the simulation.
Related video that demonstrates steps for setting up, solving, and postprocessing the solution results
for a turbulent flow within a manifold:
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1.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
1.3. Problem Description
The manifold modeled here is shown in Figure 1.1: Manifold Geometry for Flow Modeling (p. 2). Hot
air flows through the three inlets at 925 K and the same inlet velocity of 10 m/s, and then exits through
the outlet. Convective heat transfer takes place between the fluid and the manifold.
Figure 1.1: Manifold Geometry for Flow Modeling
1.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
1.4.1. Preparation
1.4.2. Meshing Workflow
1.4.3. General Settings
1.4.4. Solver Settings
1.4.5. Models
1.4.6. Materials
1.4.7. Cell Zone Conditions
1.4.8. Boundary Conditions
1.4.9. Solution
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Setup and Solution
1.4.1. Preparation
To prepare for running this tutorial:
1.
Download the exhaust_manifold.zip file here.
2.
Unzip manifold.zip to your working directory.
The SpaceClaim CAD file manifold.scdoc can be found in the folder. In addition, the manifold.pmdb file is available for use on the Linux platform.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Meshing in the top-left selection list to start Fluent in Meshing Mode.
5.
Enable Double Precision under Options.
6.
Set Meshing Processes and Solver Processes to 4 under Parallel (Local Machine).
1.4.2. Meshing Workflow
1. Start the meshing workflow.
a. In the Workflow tab, select the Watertight Geometry workflow.
b. Review the tasks of the workflow.
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Each task is designated with an icon indicating its state (for example, as complete, incomplete, etc. All tasks are initially incomplete and you proceed through the workflow completing all tasks. Additional tasks are also available for the workflow.
2. Import the CAD geometry (manifold.scdoc).
a. Select the Import Geometry task.
b. For File Format, keep the default setting of CAD.
c. For Units, keep the default setting as mm.
d. For File Name, enter the path and file name for the CAD geometry that you want to import
(manifold.scdoc).
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Setup and Solution
Note:
The workflow only supports *.scdoc (SpaceClaim), Workbench (.agdb), and the
intermediary *.pmdb file formats.
e. Select Import Geometry.
This will update the task, display the geometry in the graphics window, and allow you to proceed
onto the next task in the workflow.
Note:
Alternatively, you can use the ... button next to File Name to locate the CAD geometry file, after which, the Import Geometry task automatically updates, displaying
the geometry in the graphics window, and the workflow automatically progresses
to the next task.
Throughout the workflow, you are able to return to a task and change its settings using either the
Edit button, or the Revert and Edit button.
3. Add local sizing.
a. In the Add Local Sizing task, you are prompted as to whether or not you would like to add
local sizing controls to the faceted geometry.
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b. For the purposes of this tutorial, you can keep the default setting of no.
c. Click Update to complete this task and proceed to the next task in the workflow.
4. Generate the surface mesh.
a. In the Generate the Surface Mesh task, you can set various properties of the surface mesh
for the faceted geometry.
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Setup and Solution
b. For the purposes of this tutorial, you can keep the default settings.
Note:
The red boxes displayed on the geometry in the graphics window are a graphical
representation of size settings. These boxes change size as the values change, and
they can be hidden by using the Clear Preview button.
c. Click Generate the Surface Mesh to complete this task and proceed to the next task in the
workflow.
5. Describe the geometry.
When you select the Describe Geometry task, you are prompted with questions relating to the
nature of the imported geometry.
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a. Since a fluid region is extracted from the solid model and capping surfaces are added,
the default settings are appropriate.
b. Click Describe Geometry to complete this task and proceed to the next task in the
workflow.
6. Cover any openings in your geometry.
Select the Enclose Fluid Regions (Capping) task where you can cover or cap any openings in
your geometry in order to later extract the enclosed fluid region.
a. Create a cap for the inlets.
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Setup and Solution
i.
In the Name field, assign a name for the capping surface (for example, inlet) to be
assigned to all of the manifold's inlets.
ii. For the Zone Type, keep the default setting of velocity-inlet.
iii. For the Select By field, keep the default setting of label.
iv. In the list of labels, select in1, in2, and in3 for the openings that you want to cover.
For occasions when the list of items is long, you can use the Filter Text option and use
an expression such as in* to show only items starting with "in". Alternatively, you can
use the Use Wildcard option to list and pres-select matching items. See Filtering Lists and
Using Wildcards for more information.
The graphics window indicates the selected items.
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v. Click Create Cap(s) to complete this task and proceed to the next task in the workflow.
b. Create a cap for the outlet.
i.
In the Name field, assign a name for the capping surface (for example, outlet) to
be assigned to the manifold's outlet.
ii. For the Zone Type, change the setting to pressure-outlet.
iii. For the Select By field, keep the default setting of label.
iv. In the list of labels, select out1 for the outlet that you want to cover.
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v. Click Create Cap(s) to complete this task.
Now, all of the openings in the geometry are covered.
7. Create the fluid region.
a. Select the Create Regions task, where you can determine the number of fluid regions that
need to be extracted. ANSYS Fluent attempts to determine the number of fluid regions to
extract automatically.
b. For the Estimated Number of Fluid Regions, keep the default selection of 1.
c. Click Create Regions.
8. Update your regions.
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Fluid Flow in an Exhaust Manifold
a. Select the Update Regions task, where you can review the names and types of the various
regions that have been generated from your imported geometry, and change them as needed.
b. Keep the default settings, and click Update Regions.
Aside from fluid regions and solid regions, you can also have voids within your geometry that are
designated as dead regions. As you can see, there are four dead regions that correspond to the
four bolt holes near the outlet, a solid region and a fluid region.
Once the regions have been updated, the fluid region is displayed by default in the graphics window.
You can use the Draw Regions button to display other options, such as drawing just the solid region,
just the dead regions, or all regions.
9. Add boundary layers.
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Setup and Solution
a. Select the Add Boundary Layers task, where you can set properties of the boundary layer
mesh.
b. Keep the default settings, and click Add Boundary Layers.
10. Generate the volume mesh.
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Fluid Flow in an Exhaust Manifold
a. Select the Generate the Volume Mesh task, where you can set properties of the volume mesh.
b. Keep the default settings, and click Generate the Volume Mesh.
ANSYS Fluent will apply your settings and proceed to generate a volume mesh for the manifold
geometry. Once complete, the mesh is displayed in the graphics window and a clipping plane is
automatically inserted with a layer of cells drawn so that you can quickly see the details of the
volume mesh.
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Setup and Solution
11. Check the mesh.
Mesh → Check
12. Save the mesh file (manifold.msh.gz).
File → Write → Mesh...
13. Switch to Solution mode.
Now that a high-quality mesh has been generated using ANSYS Fluent in meshing mode, you can
now switch to solver mode to complete the set up of the simulation.
We have just checked the mesh, so select Yes when prompted to switch to solution mode.
1.4.3. General Settings
In the Mesh group box of the Domain ribbon tab, set the units for length..
Domain → Mesh → Units...
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This opens the Set Units dialog box.
1. Select length under Quantities.
2. Select mm under Units.
3. Close the Set Units dialog box.
1.4.4. Solver Settings
In the Solver group box of the Physics ribbon tab, retain the default selection of the steady pressurebased solver.
Physics → Solver
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Setup and Solution
1.4.5. Models
1. Set up your models for the CFD simulation using the Models group box of the Physics ribbon
tab.
Note:
You can also use the Models task page, which can be accessed from the tree by expanding Setup and double-clicking the Models tree item.
2. Enable heat transfer by activating the energy equation.
Setup → Models → Energy On
3. Retain the default k-ω SST turbulence model.
You will use the default settings for the k-ω SST turbulence model, so you can enable it directly from
the tree by right-clicking the Viscous node and choosing SST k-omega from the context menu.
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Setup → Models → Viscous
Model → SST k-omega
1.4.6. Materials
Change the default material of Aluminum to cast iron.
1. Create solid material properties for Cast Iron.
Setup → Materials → Solid → Aluminum
Edit...
a. Change the name of the material to be cast-iron.
b. Clear the Chemical Formula field.
c. Change the Density to 7150 kg/m3.
d. Change the Cp to 460 j/kg-k.
e. Change the Thermal Conductivity to 50 w/m-k.
f.
Click Change/Create and overwrite the Aluminum material.
g. Click Yes to replace the Aluminum material.
h. Close the Create/Edit Materials dialog box.
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Setup and Solution
1.4.7. Cell Zone Conditions
Ordinarily, you would set up the cell zone conditions for the CFD simulation using the Zones group
box of the Physics ribbon tab.
The properties of air for the fluid zone and cast-iron for the solid zone will be used.
1.4.8. Boundary Conditions
1. Set the velocity, turbulence, and thermal boundary conditions for the first inlet (inlet).
Setup → Boundary Conditions → Inlet → inlet
Edit...
a. Enter 10 m/s for Velocity Magnitude.
b. In the Turbulence group box, select Intensity and Hydraulic Diameter from the Specification
Method drop-down list.
c. Enter 10 % for the Turbulent Intensity.
d. Enter 40 mm for the Hydraulic Diameter.
e. Click the Thermal tab
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f.
Enter 925 [K]
g. Click Apply and close the Velocity Inlet dialog box.
2. Apply the same conditions to the other inlets (inlet1, and inlet2).
a. Select inlet from the Boundary Conditions node of the Outline View, right-click and select
Copy from the context menu.
This opens the Copy Conditions dialog box.
b. Select inlet 1 and inlet2 from the To Boundary Zones list.
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Setup and Solution
c. Click Copy, click OK in the confirmation prompt, and close the Copy Conditions dialog box.
3. Set the boundary conditions at the outlet (outlet).
Setup → Boundary Conditions → Outlet → outlet
Edit...
a. Retain the default setting of 0 for Gauge Pressure.
b. In the Turbulence group box, select Intensity and Hydraulic Diameter from the Specification
Method drop-down list.
c. Retain the default value of 10% for the Backflow Turbulent Intensity.
d. Enter 40 mm for the Backflow Hydraulic Diameter.
e. Click Apply and close the Pressure Outlet dialog box.
4. Set the wall heat transfer boundary conditions.
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Fluid Flow in an Exhaust Manifold
Setup → Boundary Conditions → Wall → solid_up:1:69
Edit...
a. Select Convection under Thermal Conditions.
b. Enter 10 for the Heat Transfer Coefficient.
c. Enter 300 for the Free Stream Temperature.
d. Click Apply and close the Wall dialog box.
5. Apply the same conditions to the other walls (in1, in2, in3, and out1).
a. Select solid_up:1:69 from the Boundary Conditions node of the Outline View, right-click
and select Copy from the context menu.
This opens the Copy Conditions dialog box.
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Setup and Solution
b. Select in1, in2, in3, and out1 from the To Boundary Zones list.
c. Click Copy, click OK in the confirmation prompt, and close the Copy Conditions dialog box.
6. Retain the remaining default (wall and interior) boundary conditions.
1.4.9. Solution
1. Specify the discretization schemes.
In the Solution ribbon tab, click Methods... (Solution group box).
Solution → Solution → Methods...
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Fluid Flow in an Exhaust Manifold
Retain the default settings.
2. Create a surface report definition of the velocity at the outlet (outlet).
Solution → Reports → Definitions → New → Surface Report → Facet Maximum...
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Setup and Solution
Note:
You can also access the Surface Report Definition dialog box by right-clicking Report
Definitions in the tree (under Solution) and selecting New/Surface Report/Facet
Maximum... from the menu that opens.
a. Enter point-vel for the Name of the report definition.
b. Enable Report File, Report Plot, and Print to Console in the Create group box.
During a solution run, ANSYS Fluent will write solution convergence data in a report file, plot the
solution convergence history in a graphics window, and print the value of the report definition to
the console.
c. Select Velocity... and Velocity Magnitude from the Field Variable drop-down lists.
d. Select outlet from the Surfaces selection list.
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Fluid Flow in an Exhaust Manifold
e. Click OK to save the surface report definition and close the Surface Report Definition dialog
box.
The new surface report definition point-vel will appear under the Solution/Report Definitions
tree item. ANSYS Fluent also automatically creates the following items:
• point-vel-rfile (under the Solution/Monitors/Report Files tree branch)
• point-vel-rplot (under the Solution/Monitors/Report Plots tree branch)
3. Monitor the mass flow rate at the inlets.
Solution → Reports → Definitions → New → Flux Report → Mass Flow Rate...
a. Enter mass-in for the Name of the report definition.
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Setup and Solution
b. Select Mass Flow Rate under Options.
c. Select in1, in2, in3, as well as inlet, inlet1, inlet2 from the Boundaries selection list.
d. Enable Report File, Report Plot, and Print to Console in the Create group box.
e. Click OK to save the surface report definition and close the Flux Report Definition dialog
box.
The new surface report definition mass-in will appear under the Solution/Report Definitions
tree item. ANSYS Fluent also automatically creates the following items:
• mass-in-rfile (under the Solution/Monitors/Report Files tree branch)
• mass-in-rplot (under the Solution/Monitors/Report Plots tree branch)
4. Monitor the total mass flow rate through the entire domain.
Perform the same procedure as described above, naming the report mass-tot, and selecting all
boundaries.
5. Monitor the mass balance.
Use expressions to create a report definition for the mass balance using existing report definitions.
Solution → Reports → Definitions → New → Expression...
This opens the Expression Report Definition dialog box.
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Fluid Flow in an Exhaust Manifold
a. Enter mass-bal for the Name of the expression.
b. Select mass-tot from the Report Definitions drop-down list on the right.
c. Type the / operand.
d. Select mass-in from the Report Definitions drop-down list on the right.
e. Enable Report File, Report Plot, and Print to Console in the Create group box.
f.
Click OK to save the expression definition.
6. Initialize the flow field using the Initialization group box of the Solution ribbon tab.
Solution → Initialization
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Setup and Solution
a. Select Standard from the Method list.
b. Click Initialize.
7. Save the case file (manifold_solution.cas.h5).
File → Write → Case...
8. Start the calculation by adjusting the time scale factor to 5 and requesting 100 iterations in the
Solution ribbon tab (Run Calculation group box).
Solution → Run Calculation
a. Change the Time Scale Factor to 5.
b. Enter 100 for No. of Iterations.
c. Click Calculate to begin the iterations.
As the solution progresses, the mass flow rate graph flattens out, as seen in Figure 1.2: Mass Flow
Rate History (p. 30).
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Fluid Flow in an Exhaust Manifold
Figure 1.2: Mass Flow Rate History
d. Similarly, the residuals history will be plotted in the Scaled Residuals tab in the graphics
window (Figure 1.3: Residuals (p. 30)).
Figure 1.3: Residuals
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Postprocessing
9. Save the case and data files (manifold_solution.cas.h5 and manifold_solution.dat.h5).
File → Write → Case & Data...
1.5. Postprocessing
1. Display path lines highlighting the flow field (Figure 1.4: Pathlines Through the Manifold (p. 32)).
Results → Graphics → Pathlines → New...
a. Keep the default of pathlines-1 for the Name.
b. Select Particle Variables... and Time from the Color by drop-down lists.
c. Set the Path Skip value to 5.
d. Select Accuracy Control from the Options list.
e. Select inlet, inlet1, and inlet2 from the Release from Surfaces list.
f.
Click Save/Display and close the Pathlines dialog box.
The new pathlines-1 definition appears under the Results/Graphics/Pathlines tree branch. To edit
your surface definition, right-click it and select Edit... from the menu that opens.
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Fluid Flow in an Exhaust Manifold
Figure 1.4: Pathlines Through the Manifold
2. Create two clipped surfaces through the manifold geometry.
Results → Surface → Create → Iso-Clip...
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Postprocessing
a. Create Surface 1
i.
Enter clip-x-coordinate for Name.
ii. Select Mesh... and X-Coordinate from the Clip to Values of drop-down lists.
iii. Select solid_up:1:69 from the Clip Surface list.
iv. Click Compute.
v. Keep the Min value at its minimum setting, and adjust the Max value to be at its halfway
point.
vi. Click Create.
The new clip-x-coordinate definition appears under the Results/Surfaces tree branch. To edit
your surface definition, right-click it and select Edit... from the menu that opens.
b. Create Surface 2
i.
Enter clip-z-coordinate for Name.
ii. Select Mesh... and Z-Coordinate from the Clip to Values of drop-down lists.
iii. Select solid_up:1:69 from the Clip Surface list.
iv. Click Compute.
v. Keep the Min value at its minimum setting, and adjust the Max value to be at -44.0 .
vi. Click Create and close the Iso-Clip dialog box.
The new clip-z-coordinate definition appears under the Results/Surfaces tree branch. To edit
your surface definition, right-click it and select Edit... from the menu that opens.
3. Create a scene containing the mesh and the path lines.
Results → Scene
New...
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Fluid Flow in an Exhaust Manifold
a. Keep the default scene-1 for the Name.
b. Enable the pathlines-1 graphics object.
c. Create a new mesh object to add to the scene.
i.
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Click New Object and select Mesh to open the Mesh Display dialog box.
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Postprocessing
ii. Ensure that Edges is selected under the Options list.
iii. Select clip-x-coordinate under the Surfaces list.
iv. Click Save/Display and close the Mesh Display dialog box.
The new mesh-1 definition appears under the Results/Graphics/Mesh tree branch. The new
object also appears in the Scene dialog box.
d. In the Scene dialog box, set the Transparency of mesh-1 to 50.
e. Click Save & Display and close the Scene dialog box.
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Fluid Flow in an Exhaust Manifold
Figure 1.5: Scene Containing the Mesh and Pathlines Throughout the Manifold
4. Create and define contours of velocity magnitude at the outlet along with the mesh.
Results → Graphics → Contours → New...
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Postprocessing
a. Enter contour-velocity for the Name.
b. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
c. Select outlet from the Surfaces list.
d. Disable Node Values under Options.
e. Enable Draw Mesh under Options.
This displays the Mesh Display dialog box.
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Fluid Flow in an Exhaust Manifold
In the Mesh Display dialog box, deselect all surfaces, select the out1 surface, click Display and
close the dialog.
f.
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Click Save/Display and close the Contours dialog box.
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Postprocessing
Figure 1.6: Contours of Velocity Magnitude at the Outlet
5. Create an iso-surface through the manifold geometry.
Results → Surface → Create → Iso-Surface...
a. Enter mid-plane-z for Name.
b. Select Mesh... and Z-Coordinate from the Surface of Constant drop-down lists.
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Fluid Flow in an Exhaust Manifold
c. Select fluid1 and solid_up from the From Zones... list.
d. Click Compute.
The Min and Max fields display the Z extents of the domain.
e. Enter -44 for the Iso-Values.
f.
Click Create and close the Iso-Surface dialog box.
6. Create and define a contour of temperature along the mid-plane.
Results → Graphics → Contours → New...
a. Enter contour-temperature for the Name.
b. Select Temperature... and Static Temperature from the Contours of drop-down lists.
c. Select inlet, inlet1, inlet2, mid-plane-z, outlet, and out1 from the Surfaces list.
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Postprocessing
d. Enable Draw Mesh under Options.
In the Mesh Display dialog box, deselect all surfaces, select the clip-z-coordinate surface, click
Display and close the dialog.
e. Click Save/Display and close the Contours dialog box.
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Fluid Flow in an Exhaust Manifold
Figure 1.7: Contours of Temperature at the mid-plane
7. Create and define a contour of temperature for the manifold geometry.
Results → Graphics → Contours → New...
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Postprocessing
a. Enter contour-temperature-manifold for the Name.
b. Select Temperature... and Static Temperature from the Contours of drop-down lists.
c. Select the Wall group from the Surfaces list.
Click
to deselect all surfaces. Click
surfaces by type, as shown above.
and select Surface Type under Group By to list the
d. Click Save/Display and close the Contours dialog box.
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Fluid Flow in an Exhaust Manifold
Figure 1.8: Contours of Temperature on the Exhaust Manifold
8. Save the case and data files (manifold_solution.cas.h5 and manifold_solution.dat.h5).
File → Write → Case & Data...
You will use these case and data files in Fluent Postprocessing : Exhaust Manifold (p. 45).
1.6. Summary
In this tutorial, you learned how to import a CAD geometry, generate a volume mesh, and set up, solve,
and postprocess a CFD problem involving air flow and heat transfer through a manifold all within a
single ANSYS Fluent interface.
Related video that demonstrates steps for setting up, solving, and postprocessing the solution results
for a turbulent flow within a manifold:
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Chapter 2: Fluent Postprocessing : Exhaust Manifold
This tutorial is divided into the following sections:
2.1. Introduction
2.2. Prerequisites
2.3. Problem Description
2.4. Setup and Solution
2.5. Summary
2.1. Introduction
Licensing Capability:
This tutorial is fully supported at all licensing levels.
This tutorial demonstrates the postprocessing capabilities of Fluent using a 3D model of an exhaust
manifold with high temperature flows passing through. The flow through the manifold is turbulent and
involves conjugate heat transfer.
The heat transfer involves conduction in the manifold and conduction and convection in the exhaust
fluid. The physics of conjugate heat transfer such as this are common in many engineering applications,
including the design of vehicle engines.
In this tutorial, you will read the case and data files that you created in performing the "Fluid Flow in
an Exhaust Manifold" tutorial and perform a number of postprocessing exercises.
This tutorial demonstrates how to do the following:
• Add lights to the display at multiple locations.
• Create surfaces for the display of 3D data.
• Display filled contours of temperature on several surfaces.
• Display velocity vectors.
• Create animations.
• Create a scene.
• Display results on successive slices of the domain.
• Display pathlines.
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Fluent Postprocessing : Exhaust Manifold
• Plot quantitative results.
• Overlay and explode a display.
• Annotate the display.
2.2. Prerequisites
This tutorial is written with the assumption that you have completed the Fluid Flow in an Exhaust
Manifold (p. 1) tutorial found in this manual and that you are familiar with the ANSYS Fluent tree and
ribbon structure. Some steps in the setup and solution procedure will not be shown explicitly.
2.3. Problem Description
The problem considered is shown schematically in Figure 2.1: Manifold Geometry for Flow Modeling (p. 46). The configuration consists of three inlets and one outlet. Hot exhaust gases are pushed
through each inlet and mix before leaving through the outlet. Conjugate heat transfer takes place
between the manifold and the surrounding ambient air.
As shown in the figure, air at 10 m/s is pushed through each inlet at a gas temperature of 900 K. The
outlet has a static pressure of 0 Pa.
Figure 2.1: Manifold Geometry for Flow Modeling
2.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
2.4.1. Preparation
2.4.2. Reading the Mesh
2.4.3. Manipulating the Mesh in the Viewer
2.4.4. Adding Lights
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Setup and Solution
2.4.5. Creating Isosurfaces
2.4.6. Generating Contours
2.4.7. Generating Velocity Vectors
2.4.8. Creating an Animation
2.4.9. Creating a Scene With Multiple Graphics Features
2.4.10. Creating Exploded Views
2.4.11. Animating the Display of Results in Successive Streamwise Planes
2.4.12. Generating XY Plots
2.4.13. Creating Annotation
2.4.14. Saving Picture Files
2.4.15. Generating Volume Integral Reports
2.4.1. Preparation
To prepare for running this tutorial:
1.
Navigate to the working directory where you completed the "Fluid Flow in an Exhaust Manifold"
tutorial.
2.
Use the Fluent Launcher to start ANSYS Fluent.
3.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
4.
Select 3D under Dimension.
5.
Enable Double Precision under Options.
6.
Set Solver Processes to 4 under Parallel (Local Machine).
2.4.2. Reading the Mesh
1. Read in the case and data files manifold_solution.cas.h5 and manifold_solution.dat.h5.
File → Read → Case & Data...
When you select the case file, Fluent will read the data file automatically.
2.4.3. Manipulating the Mesh in the Viewer
1. Display the mesh surfaces.
Domain → Mesh → Display...
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Fluent Postprocessing : Exhaust Manifold
a. Select the Edges option and retain the default Faces option in the Options group box.
b. Deselect all surfaces an then select all the wall surfaces by selecting the Wall surface type.
Click
to deselect all surfaces. Click
surfaces by type, as shown above.
and select Surface Type under Group By to list the
c. Click the Colors... button to open the Mesh Colors dialog box.
i.
Select Color by ID in the Options group box.
ii. Click Reset Colors to reset the mesh colors to the default settings and close the Mesh
Colors dialog box.
d. Click Display.
2. Rotate and adjust the magnification of the view.
Use the left mouse button to rotate the view. Use the middle mouse button to adjust the magnification
until you obtain an enlarged display of the exhaust manifold, as shown in Figure 2.2: Mesh Display of
the Exhaust Manifold (p. 49).
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Setup and Solution
Figure 2.2: Mesh Display of the Exhaust Manifold
Extra:
You can click the right mouse button on one of the mesh boundaries displayed in the
graphics window and its surface group, ID, and name will be displayed in the console.
This feature is especially useful when you have several zones of the same type and you
want to distinguish between them.
3. Display the mesh faces.
Domain → Mesh → Display...
a. Disable Edges in the Options group box.
b. Click Display and close the Mesh Display dialog box.
2.4.4. Adding Lights
1. Add lighting effects.
The default light settings add a white light at the position (1, 1, 1). The default light is defined in the
Lights dialog box by the Light ID 0 with Direction vectors (X, Y, Z) as (1, 1, 1).
View → Display → Lights...
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Fluent Postprocessing : Exhaust Manifold
a. Make sure that the Light On option is enabled in the Lighting Attributes group box.
b. Retain the selection of Automatic from the Lighting Method drop-down list.
Flat is the most basic lighting whereas Gouraud gives better color gradation. Note that Gouraud
rounds off corners, and so should be used with caution on highly angular geometries.
c. Click Apply and close the Display Options dialog box.
Shading will be added to the surface mesh display (Figure 2.3: Graphics Window with Default
Lighting (p. 51)).
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Setup and Solution
Figure 2.3: Graphics Window with Default Lighting
2. Add lights in two directions, (-1, 1, 1) and (-1, 1, -1).
View → Graphics → Lights...
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Fluent Postprocessing : Exhaust Manifold
You can also open the Lights dialog box by clicking the Lights... button in the Display Options dialog
box.
a. Set Light ID to 1.
b. Enable Light On.
c. Enter -1, 1, and 1 for X, Y, and Z respectively in the Direction group box.
d. Retain the selections of Automatic in the Lighting Method and Headlight On drop-down
lists.
e. Click Apply.
The Headlight On option provides constant lighting effect from a light source directly in front of
the model, in the direction of the view. You can turn off the headlight by selecting Off in the
Headlight On drop-down list (the results of this action are shown in Figure 2.4: Display with Additional Lighting: - Headlight Off (p. 52)).
Figure 2.4: Display with Additional Lighting: - Headlight Off
f.
Similarly, add a second light (Light ID= 2 with Light On enabled) with a Direction of (-1, 1,
-1). Click Apply.
The result will be more softly shaded display (Figure 2.5: Display with Additional Lighting (p. 53)).
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Setup and Solution
Figure 2.5: Display with Additional Lighting
g. Close the Lights dialog box.
Extra:
You can use the left mouse button to rotate the ball in the Active Lights window to gain
a perspective view on the relative locations of the lights that are currently active, and see
the shading effect on the ball at the center.
You can also change the color of one or more of the lights by selecting the color from the
Color drop-down list or by moving the Red, Green, and Blue sliders.
2.4.5. Creating Isosurfaces
To display results in a 3D model, you will need surfaces on which the data can be displayed. Fluent creates
surfaces for all boundary zones automatically.
You can define additional surfaces for viewing the results, such as a plane in Cartesian space. In this exercise,
you will create a plane cutting through the middle of the manifold, and at the outlet. You can use these
surfaces to display the temperature and velocity fields.
1. Create iso-surfaces of constant coordinates.
Results → Surface → Create → Iso-Surface...
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Fluent Postprocessing : Exhaust Manifold
a. Enter outlet-plane for New Surface Name.
Tip:
When you are creating multiple postprocessing surfaces, it can be helpful to group
surfaces by type for viewing in lists (Click
and select Surface Type under Group
By). All iso-surfaces will be grouped together.
b. Select Mesh... and Y-Coordinate from the Surface of Constant drop-down lists.
c. Click Compute.
The Min and Max fields display the Y extents of the domain.
d. Enter -125.0188 for the Iso-Values.
e. Click Create.
2.
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Results → Surface → Create → Iso-Surface...
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Setup and Solution
a. Enter mid-plane-x for New Surface Name.
b. Select Mesh... and X-Coordinate from the Surface of Constant drop-down lists.
c. Click Compute.
The Min and Max fields display the Y extents of the domain.
d. Enter -174 for the Iso-Values.
e. Click Create and close the Iso-Surface dialog box.
3. Create clipped surfaces through the inner manifold geometry.
Results → Surface → Create → Iso-Clip...
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Fluent Postprocessing : Exhaust Manifold
a. Enter clip-z-inner for Name.
b. Select Mesh... and Z-Coordinate from the Clip to Values of drop-down lists.
c. Select solid_up:1:69:673 from the Clip Surface list. Note the number may be different due
to mesh generation
d. Click Compute.
e. Enter -44 for the Min value and leave the Max value at its maximum.
f.
Click Create and close the Iso-Clip dialog box.
The new clip-z-inner definition appears under the Results/Surfaces tree branch. To edit your
surface definition, right-click it and select Edit... from the menu that opens.
2.4.6. Generating Contours
1. Display filled contours of temperature on the mid-plane and the outlet (Figure 2.6: Filled Contours
of Temperature on the Mid-Plane-x and the Outlet (p. 59)). Access the contour plot that was
defined in the simulation tutorial for this case.
Results → Graphics → Contours → contour-temperature
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Edit...
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Setup and Solution
a. Click
to deselect all surfaces.
b. Click
type).
and select Surface Type under Group By (if surfaces are not already grouped by
c. Select mid-plane-x and outlet-plane (under Iso-Surface in the Surfaces selection list.)
d. Enable Draw Mesh under Options.
This displays the Mesh Display dialog box.
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Fluent Postprocessing : Exhaust Manifold
In the Mesh Display dialog box, deselect all surfaces and select the clip-x-coordinate surface.
e. Enable Edges option in the Options group box.
f.
Click Display and close the Mesh Display dialog box.
g. Click Save/Display and close the Contours dialogue box.
h. Rotate and adjust the magnification of the view using the left and middle mouse buttons, respectively, to obtain the view as shown in Figure 2.6: Filled Contours of Temperature on the
Mid-Plane-x and the Outlet (p. 59).
Tip:
If the model disappears from the graphics window at any time, or if you are having
difficulty manipulating it with the mouse, do one of the following:
• Click the Fit to Window button in the graphics toolbar.
• Open the Views dialog box by right-clicking Graphics in the tree (under
Results) and selecting Views... from the menu that opens, and then use
the Default button to reset the view. You could also click Camera... in this
dialog box to open the Camera Parameters dialog box, where you could
select orthographic from the Projection drop-down list to reduce the
likelihood of zooming through the geometry.
• Press the Ctrl + L to revert to a previous view.
The inlet streams don't mix in the manifold as shown by the inlet streams not mixing together.
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Setup and Solution
Figure 2.6: Filled Contours of Temperature on the Mid-Plane-x and the Outlet
In Figure 2.6: Filled Contours of Temperature on the Mid-Plane-x and the Outlet (p. 59), the high temperatures in the exhaust stream drastically increase the temperature of the cast iron manifold. You
can also display other quantities such as velocity magnitude or pressure using the Contours dialog
box.
2. Display filled contours of temperature for the surface of the manifold(Figure 2.7: Filled Contours
of Temperature for the Surface of the Manifold (p. 60)).
Results → Graphics → Contours → contour-temperature-manifold
Edit...
a. Deselect Global Range.
b. Click Save/Display and close the Contours dialogue box.
c. Click the Fit to Window button in the graphics toolbar.
d. The surface of the manifold heats up to over 700 K from from an initial temperature of 300 K (Figure 2.7: Filled Contours of Temperature for the Surface of the Manifold (p. 60)).
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Fluent Postprocessing : Exhaust Manifold
Figure 2.7: Filled Contours of Temperature for the Surface of the Manifold
Tip:
You can increase/decrease the size of the colormap by dragging the corners of the box
that appears when you hover over the colormap.
2.4.7. Generating Velocity Vectors
Velocity vectors provide an excellent visualization of the flow through the manifold, depicting details of
the flow structure.
1. Display velocity vectors on the mid-plane through the manifold (Figure 2.8: Velocity Vectors in the
Mid-Plane of the Manifold (p. 62)).
Results → Graphics → Vectors → New...
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Setup and Solution
a. Enter velocity-vector for Vector Name.
b. Confirm that Velocity is selected under Vectors of and that Color by is set to Velocity... and
Velocity Magnitude.
c. Ensure Global Range, Auto Range, and Auto Scale are the only enabled Options.
d. Enter 1 for Scale.
e. Click
x.
f.
to deselect all surfaces from the Surfaces selection list and then select mid-plane-
Click Save/Display and close the Vectors dialog box.
g. Orient the view to display the vectors.
2. Rotate and adjust the magnification of the view to match (Figure 2.8: Velocity Vectors in the MidPlane of the Manifold (p. 62)).
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Fluent Postprocessing : Exhaust Manifold
Figure 2.8: Velocity Vectors in the Mid-Plane of the Manifold
3. Plot velocity vectors along the mid z-direction plane manifold coloured by temperature (Figure 2.9: Velocity Vectors mid-plane in the z-direction (p. 64)).
Results → Graphics → Vectors → New...
a. Enter velocity-vector-2 for Vector Name.
b. Enable Draw Mesh in the Options group box to open the Mesh Display dialog box.
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Setup and Solution
i.
Ensure that Faces is enabled and that Edges is disabled in the Options group box.
ii. Deselect all surfaces and select clip-z-coordinate from the Surfaces selection list.
iii. Click the Colors... button to open the Mesh Colors dialog box.
A. Select Color by Type in the Options group box.
B. Select surface from the Types selection list.
C. Select light-blue from the Colors selection list and close the Mesh Colors dialog box.
iv. Click Display and close the Mesh Display dialog box.
c. Select arrow from the Style drop-down list.
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Fluent Postprocessing : Exhaust Manifold
d. Enter 0.5 for Scale.
e. Deselect all surfaces.
f.
Select mid-plane-z from the Surfaces selection list.
g. Click Save/Display and close the Vectors dialog box.
h. Rotate the view and increase the magnification to obtain the view as shown in Figure 2.9: Velocity Vectors mid-plane in the z-direction (p. 64).
Figure 2.9: Velocity Vectors mid-plane in the z-direction
2.4.8. Creating an Animation
Using Fluent, you can animate the solution. For information on animating the solution, see Modeling
Transient Compressible Flow (p. 335). In this tutorial, you will animate between static views of the graphics
window.
You will display the surface temperature distribution on the inner part of the manifold along with the
temperatures of the outlet flow and mid-plane flow. You will also create the key frames and view the
transition between the key frames, dynamically, using the animation feature.
1. Display filled contours of surface temperature on the mid-plane, inner-clip, and outlet-plane.
(Figure 2.10: Filled Temperature Contours on the mid-plane-x, clip-z-inner and outlet-plane Surfaces (p. 66)).
Results → Graphics → Contours → contour-temperature
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Edit...
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Setup and Solution
a. Select Banded from the Coloring group box.
b. Retain the selection of Temperature... and Static Temperature from the Contours of dropdown lists.
c. Deselect all surfaces.
d. Select clip-z-inner, mid-plane-x, and outlet-plane from the Surfaces selection list.
e. Click Save/Display and close the Contours dialog box.
f.
Reorient the display as needed to obtain the view shown in Figure 2.10: Filled Temperature
Contours on the mid-plane-x, clip-z-inner and outlet-plane Surfaces (p. 66).
Figure 2.10: Filled Temperature Contours on the mid-plane-x, clip-z-inner and outlet-plane Surfaces (p. 66) shows the high temperature exhaust heating the walls of the manifold.
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Figure 2.10: Filled Temperature Contours on the mid-plane-x, clip-z-inner and outlet-plane
Surfaces
2. Create the key frames by changing the point of view.
Results → Animation → Scene Animation...
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You will use the current display (Figure 2.10: Filled Temperature Contours on the mid-plane-x, clip-zinner and outlet-plane Surfaces (p. 66)) as the starting view for the animation (Frame = ).
a. Click Add in the Key Frames group box to create the first frame for your animation.
This will store the current display as Key-1.
b. Magnify the view to focus on the outlet region.
c. Enter 100 for Frame in the Key Frames group box.
d. Click Add to create the one-hundredth frame for your animation.
This will store the new display as Key-100.
The magnified view will be the one-hundredth key frame of the animation, with intermediate displays
(2 through 99) to be filled in during the animation.
e. Rotate the view and adjust the magnification so that the backside of the manifold is visible
from an angle (Figure 2.11: Filled Temperature Contours on the Mid-Plane, Inner-Clip, and
Outlet-Plane Surfaces (p. 68)).
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Figure 2.11: Filled Temperature Contours on the Mid-Plane, Inner-Clip, and Outlet-Plane
Surfaces
f.
Enter 200 for Frame.
g. Click Add to create the two-hundredth frame for your animation.
This will store the new display as Key-200.
Note:
You can check the display view of any of your saved key frames by selecting it in
the Keys list.
3. View the scene animation by clicking the play button (
) in the Playback group box.
While effective animation is best conducted on high-end graphics workstations, you can view scene
animations on any workstation. If the graphics display speed is slow, the animation playback will take
some time and will appear choppy, with the redrawing very obvious. On fast graphics workstations,
the animation will appear smooth and continuous and will provide an excellent visualization of the
display from a variety of spatial orientations. On many machines, you can improve the smoothness
of the animation by enabling the Double Buffering option in the Display Options dialog box.
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To produce a slower animation, increase the number of frames between the key frames. The more
sparsely you place your key frames, the more transition frames Fluent creates between the key frames
and therefore stretching out your animation.
Note:
You can also make use of animation tools of Fluent for transient cases as demonstrated
in Modeling Transient Compressible Flow (p. 335).
Extra:
You can change the Playback Mode if you want to auto repeat or auto reverse the
animation. When you are in either of these modes, you can click the stop button (
to stop the continuous animation.
)
4. Close the Animate dialog box.
2.4.9. Creating a Scene With Multiple Graphics Features
Scenes allow you to display multiple graphics plots in a single window.
1. Create a scene displaying contours and vector plots in a single window.
a. Edit contour-temperature to use the clip-z-inner and outlet-plane as the display surface.
Click Save/Display.
b. Edit velocity-vector to use the mid-plane-z as the display surface and reduce the Scale to 1.
Click Save & Display.
c. Open the previously created scene scene-1.
Results → Scene → scene-1
Edit...
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d. Deselect any previously selected graphics objects.
e. Select contour-temperature and velocity-vector.
f.
In the Scene dialog box, set the Transparency for contour-temperature to 30.
g. Click Save & Display to create the scene and display it in the graphics window, and close the
Scene dialog box.
h. Drag the velocity vector colormap to the left of the graphics window and drag the temperature
colormap to the bottom of the graphics window and modify the orientation and zoom of the
scene to match Figure 2.12: Temperature Contours and Velocity Vectors Scene (p. 71).
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i.
Figure 2.12: Temperature Contours and Velocity Vectors Scene
2.4.10. Creating Exploded Views
The Scene Description dialog box stores each display that you request and allows you to manipulate the
displayed items individually. This capability can be used to generate exploded views, in which results are
translated or rotated out of the physical domain for enhanced display. As shown in the Scene Description
dialog box, you can experiment with this capability by displaying side-by-side velocity vectors, pathlines,
and temperature contours.
1. Create a Scene comprised of various graphical features.
a. Edit velocity-vector to use the clip-z-inner as the display surface and reduce the Scale to 1.
Click Save & Display.
b. Open the Scene dialog box.
Results → Scene
New...
c. Enable the features pathlines-1, velocity-vector, and contour-temperature.
d. Click Save & Display and close the Scene dialog box.
2. Transform the features to form an exploded view.
View → Graphics → Compose...
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a. Select both temperature contour plots in the Names list.
b. Click Display... in the Geometry Attributes group box and disable the Nodes option.
c. Click Apply and close the Display Properties dialog box.
d. Click Transform... in the Geometry Attributes options box.
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e. Enter 135 for Y in the Translate group box.
f.
Click Apply and close the Transformations dialog box.
g. In the Scene Description dialog box, deselect all names and select velocity_vector.
h. Click Transform..., and in the Transformations dialog box, enter 100 for Z under the Translate
heading.
i.
Click Apply and close both the Transformations dialog box and the Scene Description dialog
box.
j.
Click, drag and drop the color maps as shown.
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Figure 2.13: Exploded Scene Display of Temperature, Velocity, and Pathlines
2.4.11. Animating the Display of Results in Successive Streamwise Planes
You may want to march through the flow domain, displaying a particular variable on successive slices of
the domain. While this task could be accomplished manually, plotting each plane in turn, or using the
Scene Description and Animate dialog boxes, here you will use the Sweep Surface dialog box to facilitate
the process. To illustrate the display of results on successive slices of the domain, you will plot contours of
temperature on planes along the z-axis.
1. Delete the vectors and temperature contours from the display.
Click the Close Tab button ( ) to clear the graphics window (located on the upper right-hand
side of the graphics window tab).
2. Generate contours of temperature and sweep them through the domain along the X axis.
Results → Animation → Sweep Surface...
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a. Change X to be 0 and Z to be 1.
b. Click Compute.
c. Retain the default value of -0.1018232 m for Initial Value in the Animation group box.
d. Retain 0.01343616 m for Final Value.
Warning:
The units for the initial and final values are in meters, regardless of the length
units being used in the model. Here, the initial and final values are set to the
Min Value and Max Value, to generate an animation through the entire domain.
e. Enter 200 for Frames.
f.
Select Contours from the Display Type selection list to open the Contours dialog box.
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i.
Enable Filled in the Options group box.
ii. Select Temperature... and Static Temperature from the Contours of drop-down lists.
iii. Deselect all surfaces and select clip-x-coordinate from the Surfaces drop-down list.
iv. Click OK to close the Contours dialog box.
g. Click Animate and close the Sweep Surface dialog box.
You will see the temperature contour plot displayed at 200 successive streamwise planes. Fluent will
automatically interpolate the contoured data on the streamwise planes between the specified end
points. Especially on high-end graphics workstations, this can be an effective way to study how a flow
variable changes throughout the domain.
Note:
You can also make use of animation tools of Fluent for transient cases as demonstrated
in Modeling Transient Compressible Flow (p. 335).
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2.4.12. Generating XY Plots
XY plotting can be used to display quantitative results of your CFD simulations. Here, you will complete
the review of the manifold heat transfer simulation by plotting the temperature variation through a solid
portion of the manifold.
1. Define the rake along which to plot results.
Results → Surface → Create → Line/Rake...
a. Enter rake-solid for New Surface Name.
b. Select rake from the Type drop-down list.
c. Enter 100 for the Number of Points option.
d. Enter the coordinates of the rake using a starting coordinate of (-145, -105, -44) and an
ending coordinate of (-120, -105, -44) in the End Points group box.
These coordinates define a line through a solid portion of the manifold located slightly above the
outlet.
e. Click Create and close the Line/Rake Surface dialog box.
2. Plot the temperature distribution along the rake through a solid region. (Figure 2.14: Temperature
Along a Solid Portion of the Manifold (p. 80)).
Results → Plots → XY Plot → New...
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a. Enter xy-plot for XY Plot Name.
b. Retain the default Plot Direction of (1, 0, 0).
c. Select Temperature... and Static Temperature from the Y Axis Function drop-down lists.
d. Select rake-solid from the Surfaces selection list.
This will plot temperature vs. the X coordinate along the selected rake (rake-solid).
e. Click the Axes... button to open the Axes - Solution XY Plot dialog box.
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i.
Retain the selection of X in the Axis list.
ii. Select general in the Type group box.
iii. Set Precision to 3.
iv. Click Apply and repeat for Y.
v. Click Apply and close the Axes - Solution XY Plot dialog box.
f.
Click Save/Plot and close the Solution XY Plot dialog box.
The temperature distribution (Figure 2.14: Temperature Along a Solid Portion of the Manifold (p. 80))
shows that the solid portion of the manifold saw similar temperatures through the thickness.
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Figure 2.14: Temperature Along a Solid Portion of the Manifold
2.4.13. Creating Annotation
You can annotate the display with the text of your choice.
View → Graphics → Annotate...
1. Enter the text describing the plot (for example, Temperature in a Solid Portion of
the Manifold) in the Annotation Text field.
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2. Select 20 from the Size drop-down list in the Font Specification group box.
3. Click Add.
A Working dialog box will appear telling you to select the desired location of the text using the mouseprobe button.
4. Click the right mouse button in the graphics window where you want the text to appear, and you
will see the text displayed at the selected location (Figure 2.15: A Display with Annotation (p. 81)).
Extra:
If you want to move the text to a new location on the screen, select the text in the
Names selection list, click Delete Text, and click Add once again, defining a new position with the mouse.
Note:
Depending on the size of the graphics window and the picture file format you choose,
the font size of the annotation text you see on the screen may be different from the
font size in a picture file of that graphics window. The annotation text font size is absolute, while the rest of the items in the graphics window are scaled to the proportions
of the picture file.
Figure 2.15: A Display with Annotation
5. Close the Annotate dialog box.
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6. Save the case file (manifold_solution.cas.h5).
File → Write → Case...
2.4.14. Saving Picture Files
You can save picture files of the graphics window in many different formats, including PostScript, encapsulated PostScript, TIFF, PNG, PPM, JPEG, VRML and window dumps. Here, the procedure for saving a color
PostScript file is shown.
Click the Save Picture icon-
in the toolbar to open the Save Picture dialog box.
1. Select JPEG from the Format list.
2. Retain the default selection of Color from the Coloring list.
3. Click the Save... button to open the Select File dialog box.
a. Enter a name for Hardcopy File.
b. Click OK to close the Select File dialog box.
4. Close the Save Picture dialog box.
2.4.15. Generating Volume Integral Reports
Reports of volume integrals can be used to determine the volume of a particular fluid region (that is, a
fluid zone), the sum of quantities, or the maximum and minimum values of particular variables. Here we
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Summary
will use the volume integral reports to determine the mass of the air in the manifold and the maximum
temperature of the manifold.
Results → Reports → Volume Integrals...
1. Select Mass from the Report Type list.
2. Select fluid1 from the Cell Zones selection list.
3. Click Compute to calculate the total mass of the air in the manifold.
The mass of the air in the fluid1 cell zone is displayed.
4. Select Maximum in the Report Type group box.
5. Select Temperature... and Static Temperature from the Field Variable drop-down lists.
6. Select solid_up from the Cell Zones selection list.
The maximum temperature in the solid_up cell zone is displayed.
7. Repeat the previous operation to determine the minimum temperature in the solid_up cell zone.
The maximum and minimum temperatures are an important characteristic of exhaust manifold design.
2.5. Summary
This tutorial demonstrated the use of many of the extensive postprocessing features available in Fluent.
For more information on these and related features, see reporting alphanumeric data and displaying
graphics in the Fluent User's Guide.
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Chapter 3: Modeling Flow Through Porous Media
This tutorial is divided into the following sections:
3.1. Introduction
3.2. Prerequisites
3.3. Problem Description
3.4. Setup and Solution
3.5. Summary
3.1. Introduction
Licensing Capability:
This tutorial is fully supported at all licensing levels.
Many industrial applications such as filters, catalyst beds, and packing, involve modeling the flow through
porous media. This tutorial illustrates how to set up and solve a problem involving gas flow through
porous media.
The industrial problem solved here involves gas flow through a catalytic converter. Catalytic converters
are commonly used to purify emissions from gasoline and diesel engines by converting environmentally
hazardous exhaust emissions to acceptable substances. Examples of such emissions include carbon
monoxide (CO), nitrogen oxides (NOx), and unburned hydrocarbon fuels. These exhaust gas emissions
are forced through a substrate, which is a ceramic structure coated with a metal catalyst such as platinum
or palladium.
The nature of the exhaust gas flow is a very important factor in determining the performance of the
catalytic converter. Of particular importance is the pressure gradient and velocity distribution through
the substrate. Hence, CFD analysis is useful for designing efficient catalytic converters. By modeling the
exhaust gas flow, the pressure drop and the uniformity of flow through the substrate can be determined.
In this tutorial, ANSYS Fluent is used to model the flow of nitrogen gas through a catalytic converter
geometry, so that the flow field structure may be analyzed.
This tutorial demonstrates how to do the following in ANSYS Fluent:
• Use the Watertight Geometry guided workflow to:
– Import a CAD geometry
– Generate a surface mesh
– Cap inlets and outlets
– Extract a fluid region
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– Generate a volume mesh
• Set up a porous zone for the substrates with appropriate resistances.
• Calculate a solution for gas flow through the catalytic converter using the pressure-based solver.
• Plot pressure and velocity distribution on specified planes of the geometry.
For more information about using the guided workflows, see Working With Fluent Guided Workflows
in the Fluent User's Guide.
3.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
3.3. Problem Description
The catalytic converter modeled here is shown in Figure 3.1: Catalytic Converter Geometry for Flow
Modeling (p. 86). The nitrogen flows through the inlet with a uniform velocity of 125 m/s and 800K,
passes through a pair of ceramic monolith substrates with square-shaped channels, and then exits
through the outlet.
Figure 3.1: Catalytic Converter Geometry for Flow Modeling
While the flow in the inlet and outlet sections is turbulent, the flow through the substrates is laminar
and is characterized by inertial and viscous loss coefficients along the inlet axis. The substrates are impermeable in other directions. This characteristic is modeled using loss coefficients that are three orders
of magnitude higher than in the main flow direction.
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3.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
3.4.1. Preparation
3.4.2. Meshing Workflow
3.4.3. General Settings
3.4.4. Solver Settings
3.4.5. Models
3.4.6. Materials
3.4.7. Cell Zone Conditions
3.4.8. Boundary Conditions
3.4.9. Solution
3.4.10. Postprocessing
3.4.1. Preparation
To prepare for running this tutorial:
1.
Download the catalytic_converter.zip file here.
2.
Unzip catalytic_converter.zip to your working directory.
The SpaceClaim CAD file catalytic_converter.scdoc can be found in the folder. In addition,
the catalytic_converter.pmdb file is available for use on the Linux platform.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Meshing in the top-left selection list to start Fluent in Meshing Mode.
5.
Enable Double Precision under Options.
6.
Set Meshing Processes and Solver Processes to 4 under Parallel (Local Machine).
3.4.2. Meshing Workflow
1. Start the meshing workflow.
a. In the Workflow tab, select the Watertight Geometry workflow.
b. Review the tasks of the workflow.
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Each task is designated with an icon indicating its state (for example, as complete, incomplete, etc. For more information, see Understanding Task States in the Fluent User's Guide).
All tasks are initially incomplete and you proceed through the workflow completing all
tasks. Additional tasks are also available for the workflow. For more information, see
Customizing Workflows in the Fluent User's Guide.
2. Import the CAD geometry (catalytic_converter.scdoc).
a. Select the Import Geometry task.
b. For File Format, keep the default setting of CAD.
c. For Units, keep the default setting as mm.
d. For File Name, enter the path and file name for the CAD geometry that you want to import
(catalytic_converter.scdoc).
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Note:
The workflow only supports *.scdoc (SpaceClaim) and the intermediary *.pmdb
file formats.
e. Select Import Geometry.
This will update the task, display the geometry in the graphics window (Figure 3.2: The Imported
CAD Geometry for the Catalytic Converter (p. 90)), and allow you to proceed onto the next task in
the workflow.
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Figure 3.2: The Imported CAD Geometry for the Catalytic Converter
Note:
Alternatively, you can use the ... button next to File Name to locate the CAD geometry file, after which, the Import Geometry task automatically updates, displaying
the geometry in the graphics window, and the workflow automatically progresses
to the next task.
Throughout the workflow, you are able to return to a task and change its settings using either the
Edit button, or the Revert and Edit button. For more information, see Editing Tasks in the Fluent
User's Guide.
3. Add local sizing.
a. In the Add Local Sizing task, you are prompted as to whether or not you would like to add
local sizing controls to the faceted geometry.
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In this tutorial, we will add local sizing in and around the sensor, since that is an area where we
require a more refined mesh. Later, we will apply settings for a coarser surface mesh elsewhere.
b. At the prompt for adding local sizing, select yes.
c. Enter sensor for the Name of the size control.
d. Specify Curvature for the Size Control Type.
e. Specify 0.1 for the Local Min Size.
f.
Specify 1.2 for the Max Size
g. Select the faces in and around the sensor in the list, specifically, sensing_element-65solid, sensor_innertube-67-solid, and sensor_protectiontube-66-solid1.
For occasions when the list of items is long, you can use the Filter Text option and use an expression
such as in* to show only items starting with "in". Alternatively, you can use the Use Wildcard
option to list and pres-select matching items. See Filtering Lists and Using Wildcards for more information.
Select the Use Wildcard option and enter sens* in the text field to filter out the other labels
and automatically select the desired labels.
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h. Click Add Local Sizing to complete this task and proceed to the next task in the workflow.
4. Generate the surface mesh.
a. In the Generate the Surface Mesh task, you can set various properties of the surface mesh
for the faceted geometry.
b. Specify 1.5 for the Minimum Size.
Note:
The red boxes displayed on the geometry in the graphics window are a graphical
representation of size settings. These boxes change size as the values change, and
they can be hidden by using the Clear Preview button.
c. Select Advanced Options to expose additional settings.
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d. Specify no for the Invoke Zone Separation by Angle? option.
e. Specify 0.95 for the Quality Improve Skewness Limit.
f.
Click Generate the Surface Mesh to complete this task and proceed to the next task in the
workflow.
5. Describe the geometry.
When you select the Describe Geometry task, you are prompted with questions relating to the
nature of the imported geometry.
a. Select The geometry consists of both fluid and solid regions and/or voids option under
Geometry Type, since this model contains both fluid and solids, and potential voids.
b. Select Yes for the Will you cap openings and extract fluid regions? prompt, since we
plan on adding capping surfaces and extracting a fluid.
c. Select Yes for the Change all fluid-fluid boundary types from 'wall' to 'internal'?
prompt, since we are modeling flow through the entire geometry, and any interior wall
boundaries between potential fluid regions should be interior boundaries to allow the
flow to pass.
Remember that there are two regions within the catalytic converter that will ultimately represent
porous regions.- surrounded by other non-porous fluid regions For now, we will consider all
of these internal regions as fluid regions and change them accordingly in the ANSYS Fluent
solver.
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d. Keep the rest of the default settings for this task.
e. Click Describe Geometry to complete this task and proceed to the next task in the
workflow.
6. Cover any openings in your geometry.
Select the Enclose Fluid Regions (Capping) task, where you can cover, or cap, any openings in
your geometry in order to later extract the enclosed fluid region.
a. Create a cap for the inlet.
i.
Enter inlet for the Name of the capping surface to be assigned to the manifold's
inlet.
ii. For the Zone Type, keep the default setting of velocity-inlet.
iii. In the list of labels, select in1 for the opening that you want to cover (or right-click
the surface of the inlet in the graphics window).
The graphics window indicates the selected items.
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iv. Click Create Cap(s) to complete this task and proceed to the next task in the workflow.
Once completed, this particular task will return you to a fresh task in order to assign
additional capping surfaces, if necessary. We will proceed to assign a cap for the remaining opening and assign it to be an outlet.
b. Create a cap for the outlet.
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i.
Enter outlet for the Name of the capping surface to be assigned to the manifold's
outlet.
ii. For the Zone Type, change the setting to pressure-outlet.
iii. In the list of labels, select out1 for the outlet that you want to cover (or right-click the
surface of the inlet in the graphics window).
iv. Click Create Cap(s) to complete this task.
Now, all of the openings in the geometry are covered.
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7. Confirm and update the boundaries.
a. Select the Update Boundaries task, where you can inspect the mesh boundaries and confirm
and change any designated boundaries accordingly. ANSYS Fluent attempts to determine the
correct arrangement of boundaries automatically.
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b. All the proposed boundaries are correct, so click Update Boundaries. and proceed to the next
task.
8. Create the fluid region.
a. Select the Create Regions task, where you can determine the number of fluid regions that
need to be extracted. ANSYS Fluent attempts to determine the number of fluid regions to
extract automatically.
b. For the Estimated Number of Fluid Regions, enter a value of 3.
We anticipate that there will be fluid regions located at the inlet, the outlet, and the fluid region
between the substrates.
c. Click Create Regions.
The extracted fluid regions are displayed in the graphics window.
9. Update your regions.
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a. Select the Update Regions task, where you can review and change the tabulated names and
types of the various regions that have been generated from your imported geometry, and
change them as needed.
We can see that the three fluid regions are defined, however, the two regions of the individual
substrates are identified as solid regions. We can change their designations here in this task, and
provide them with useful names.
b. Change the two substrate solid regions to be fluid regions, and rename them, in the table.
i.
Under Region Name, locate the honeycomb.solid1 region, double-click and rename
the region to fluid:substrate:1.
ii. For that specific region, under Region Type, select fluid from the drop-down menu.
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c. Repeat the procedure for the honeycomb_af0-solid1 region, renaming it to fluid:substrate:2.
d. Click Update Regions to update your settings.
10. Add boundary layers.
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Setup and Solution
a. Select the Add Boundary Layers task, where you can set properties of the boundary layer
mesh.
For the Add Boundary Layers task, ensure yes is selected at the prompt as to whether or not
you want to define boundary layer settings. In this task, you can define specific details for
capturing the boundary layer in and around your geometry.
b. Keep the default settings, and click Add Boundary Layers.
11. Generate the volume mesh.
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a. Select the Generate the Volume Mesh task, where you can set properties of the volume mesh
itself.
b. Keep the default settings, and click Generate the Volume Mesh.
ANSYS Fluent will apply your settings and proceed to generate a volume mesh for the manifold
geometry. Once complete, the mesh is displayed in the graphics window and a clipping plane is
automatically inserted with a layer of cells drawn so that you can quickly see the details of the
volume mesh.
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Setup and Solution
12. Check the mesh.
Mesh → Check
13. Save the mesh file (catalytic_converter.msh.gz).
File → Write → Mesh...
14. Switch to Solution mode.
Now that a high-quality mesh has been generated using ANSYS Fluent in meshing mode, you can
now switch to solver mode to complete the set up of the simulation.
We have just checked the mesh, so select Yes when prompted to switch to solution mode.
3.4.3. General Settings
In the Mesh group box of the Domain ribbon tab, set the units for length..
Domain → Mesh → Units...
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This opens the Set Units dialog box.
1. Select length under Quantities.
2. Select mm under Units.
3. Close the Set Units dialog box.
4. Examine the mesh.
Rotate the view and zoom in to get the display shown in Figure 3.3: Mesh for the Catalytic Converter
Geometry in Fluent (Solver Mode) (p. 105).
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Setup and Solution
Figure 3.3: Mesh for the Catalytic Converter Geometry in Fluent (Solver Mode)
3.4.4. Solver Settings
Retain the default solver settings.
Physics → Solver
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3.4.5. Models
1. Allow temperatures to be considered in the calculations by enabling the energy model.
You can enable the calculation of temperatures directly from the tree by right-clicking the Energy
node and choosing On from the context menu.
Setup → Models → Energy
On
2. Retain the default k-ω SST turbulence model.
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You will use the default settings for the k-ω SST turbulence model, so you can enable it directly from
the tree by right-clicking the Viscous node and choosing SST k-omega from the context menu.
Setup → Models → Viscous
Model → SST k-omega
3.4.6. Materials
Add nitrogen to the list of fluid materials by copying it from the Fluent Database of materials.
Physics → Materials → Create/Edit...
a. Click the Fluent Database... button to open the Fluent Database Materials dialog box.
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i.
Select nitrogen (n2) in the Fluent Fluid Materials selection list.
ii. Click Copy to copy the information for nitrogen to your list of fluid materials.
iii. Close the Fluent Database Materials dialog box.
b. Click Change/Create and close the Create/Edit Materials dialog box.
3.4.7. Cell Zone Conditions
1. Set the cell zone conditions for the first fluid zone (fluid:0).
Setup → Cell Zone Conditions → Fluid → fluid:0
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a. Select nitrogen from the Material Name drop-down list.
b. Click Apply and close the Fluid dialog box.
2. Perform the same operation for the other fluid zones (fluid:1 and fluid:3).
3. Set the cell zone conditions for the first substrate (fluid:substrate:1).
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a. Select nitrogen from the Material Name drop-down list.
b. Enable Porous Zone to activate the porous zone model.
c. Enable Laminar Zone to solve the flow in the porous zone without turbulence.
d. Click the Porous Zone tab.
i.
Make sure that the principal direction vectors are set as shown in Table 3.1: Values for the
Principle Direction Vectors (p. 111).
ANSYS Fluent automatically calculates the third (Z direction) vector based on your inputs for
the first two vectors. The direction vectors determine which axis the viscous and inertial resistance
coefficients act upon.
Table 3.1: Values for the Principle Direction Vectors
Axis
Direction-1 Vector
Direction-2 Vector
X
0
0
Y
0
1
Z
1
0
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ii. For the viscous and inertial resistance directions, enter the values in Table 3.2: Values for
the Viscous and Inertial Resistance (p. 112) Viscous Resistance and Inertial Resistance.
Direction-1 and Direction-2 are set to arbitrary large numbers. These values are several orders
of magnitude greater than that of the Direction-3 flow and will make any radial flow insignificant.
Scroll down to access the fields that are not initially visible.
Table 3.2: Values for the Viscous and Inertial Resistance
Direction
Viscous Resistance (1/m2)
Inertial Resistance (1/m)
Direction-1
1e+06
1000
Direction-2
1e+06
1000
Direction-3
1e+03
1000
e. Click Apply and close the Fluid dialog box.
4. Repeat these steps for the other substrate (fluid:substrate:2).
3.4.8. Boundary Conditions
1. Set the velocity and turbulence boundary conditions at the inlet (inlet).
Setup → Boundary Conditions → Inlet → inlet
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a. Enter 125 m/s for Velocity Magnitude.
b. In the Turbulence group box, select Intensity and Hydraulic Diameter from the Specification
Method drop-down list.
c. Enter 5% for the Turbulent Intensity.
d. Enter 500mm for the Hydraulic Diameter.
e. Click the Thermal tab and enter 800 K for the Temperature of the incoming fluid.
f.
Click Apply and close the Velocity Inlet dialog box.
2. Set the boundary conditions at the outlet (outlet).
Setup → Boundary Conditions → Outlet → outlet
Edit...
a. Retain the default setting of 0 for Gauge Pressure.
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b. In the Turbulence group box, select Intensity and Hydraulic Diameter from the Specification
Method drop-down list.
c. Retain the default value of 5% for the Backflow Turbulent Intensity.
d. Enter 500 mm for the Backflow Hydraulic Diameter.
e. Click the Thermal tab and enter 800 K for the Backflow Total Temperature of the outgoing
fluid.
f.
Click Apply and close the Pressure Outlet dialog box.
3. Retain the remaining default (wall and interior) boundary conditions.
3.4.9. Solution
1. Specify the discretization schemes.
Solution → Solution → Methods...
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Retain the default settings.
2. Enable the plotting of the mass flow rate at the outlet.
Solution → Reports → Definitions → New → Surface Report → Mass Flow Rate
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a. Enter surf-mon-1 for the Name of the surface report definition.
b. In the Create group box, enable Report File, Report Plot and Print to Console.
c. Select Outlet in the Surfaces selection list.
d. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
3. Initialize the solution.
Solution → Initialization
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Setup and Solution
a. Select Standard under Method.
Warning:
Standard is the recommended initialization method for porous media simulations.
The default Hybrid method does not account for the porous media properties, and
depending on boundary conditions, may produce an unrealistic initial velocity field.
For porous media simulations, the Hybrid method should only be used when the
Maintain Constant Velocity Magnitude option is enabled in the Hybrid Initialization dialog box.
b. Click Options... to open the Solution Initialization task page, which provides access to further
settings.
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a. Select inlet from the Compute from drop-down list in the Solution Initialization task
page.
b. Retain the default settings for standard initialization method.
c. Click Initialize.
4. Save the case file (catalytic_converter.cas.h5).
File → Write → Case...
5. Start the calculation.
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Setup and Solution
Solution → Run Calculation → Run Calculation...
a. Enter 150 for No. of Iterations.
b. Click Calculate to begin the iterations.
The mass flow rate graph flattens out, as seen in Figure 3.4: Mass Flow Rate History (p. 119). Since
the mass flow rate has stabilized after 150 iterations, the solution can be said to have reached
convergence.
Figure 3.4: Mass Flow Rate History
6. Save the case and data files (catalytic_converter.cas.h5 and catalytic_converter.dat.h5).
File → Write → Case & Data...
3.4.10. Postprocessing
1. Display the wall surfaces.
Results → Graphics → Mesh... → New...
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a. Deselect all items in the Surfaces selection list, and make sure that only Wall category of
surfaces is selected.
b. Click Display and close the Mesh Display dialog box.
2. Set the lighting for the display.
View → Display → Options...
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a. Disable Double Buffering in the Rendering group box.
b. Make sure Lights On is enabled in the Lighting Attributes group box.
c. Retain the selection of Automatic from the Lighting drop-down list.
d. Click Apply and close the Display Options dialog box.
3. Set the transparency for the wall surfaces.
View → Graphics → Compose...
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a. Select all surfaces in the Names selection list.
b. Click the Display... button in the Geometry Attributes group box to open the Display
Properties dialog box.
i.
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Disable Edges, Perimeter Edges, and Nodes in the Visibility group box.
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ii. Make sure that the Red, Green, and Blue sliders are set to the maximum position (that is,
255).
iii. Set the Transparency slider to 70.
iv. Click Apply and close the Display Properties dialog box.
c. Click Apply and close the Scene Description dialog box.
4. Create a surface passing through the geometry for postprocessing purposes.
Results → Surface → Create → Plane...
a. Enter y=-425 as the New Surface Name.
b. Select ZX Plane from the Method drop-down list.
c. Enter -425 for Y.
d. Click Create.
5. Create cross-sectional planes at locations throughout the domain: in the inlet prior to the first
substrate, within the first substrate, in the fluid zone between the substrates, within the second
substrate, and just after the second substrate in the outlet.
Results → Surface → Create → Plane...
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a. Enter z=185 as the New Surface Name.
b. Select XY Plane from the Method drop-down list.
c. Enter 185 for Z.
d. Click Create.
e. Repeat these steps for the remaining surfaces at z=230, z=280, z=330, and z=375, and close
the Plane Surface dialog box.
6. Display velocity vectors on the y=-425 surface (Figure 3.5: Velocity Vectors Through the Interior (p. 127)).
Results → Graphics → Vectors → New...
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Setup and Solution
a. Enter vector-vel for Vector Name.
b. Disable Global Range under Options.
c. Enable Draw Mesh in the Options group box to open the Mesh Display dialog box.
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i.
Make sure that Wall is selected in the Surfaces selection list.
ii. Click Display and close the Mesh Display dialog box.
d. Assign a value of 0.05 for Scale.
e. Select y=-425 in the Surfaces selection list.
f.
Click Save/Display and close the Vectors dialog box.
g. Repeat the procedure in step 3 to set the transparency for the wall surfaces.
h. Rotate the view and adjust the magnification to get the display shown in Figure 3.5: Velocity
Vectors Through the Interior (p. 127).
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Setup and Solution
Figure 3.5: Velocity Vectors Through the Interior
The flow pattern shows that the flow enters the catalytic converter as a jet, with recirculation on
either side of the jet. As it passes through the porous substrates, it decelerates and straightens out,
and exhibits a more uniform velocity distribution. This allows the metal catalyst present in the
substrates to be more effective.
7. Display filled contours of static pressure on the interior plane (Figure 3.6: Contours of Static Pressure
Through the Interior (p. 129)).
Results → Graphics → Contours → New...
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Modeling Flow Through Porous Media
a. Enter contour-pressure for Contour Name.
b. Make sure that Filled, Node Values, and Boundary Values are enabled in the Options group
box.
c. Enable Draw Mesh to open the Mesh Display dialog box.
a. Make sure that Wall is selected in the Surfaces selection list.
b. Click Display and close the Mesh Display dialog box.
d. Make sure that Pressure... and Static Pressure are selected from the Contours of drop-down
lists.
e. Select y=-425 in the Surfaces selection list.
f.
Click Save/Display and close the Contours dialog box.
The pressure changes rapidly in the middle section, where the fluid velocity changes as it passes through
the porous substrates. The pressure drop can be high, due to the inertial and viscous resistance of the
porous media.
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Setup and Solution
Figure 3.6: Contours of Static Pressure Through the Interior
8. Display filled contours of the velocity magnitude on the z=185, z=230, z=280, z=330, and z=375
surfaces (Figure 3.7: Contours of Velocity Magnitude on the z=185, z=230, z=280, z=330, and z=375
Surfaces (p. 131)).
Results → Graphics → Contours → New...
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Modeling Flow Through Porous Media
a. Enter contour-vel-mag for Contour Name.
b. Make sure that Filled, Node Values, and Boundary Values are enabled in the Options group
box.
c. Disable Global Range in the Options group box.
d. Enable Draw Mesh to open the Mesh Display dialog box.
a. Make sure that Wall is selected in the Surfaces selection list.
b. Click Display and close the Mesh Display dialog box.
e. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
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Summary
f.
Select z=185, z=230, z=280, z=330, and z=375 in the Surfaces selection list, and deselect all
others.
g. Click Save/Display and close the Contours dialog box.
Figure 3.7: Contours of Velocity Magnitude on the z=185, z=230, z=280, z=330, and z=375
Surfaces
The velocity profile becomes more uniform as the fluid passes through the porous media. The velocity
is higher at the center (the area in red) just before the nitrogen enters the substrates and then decreases
as it passes through and exits the second substrate. The area in green, which corresponds to a moderate
velocity, increases in extent.
9. Save the case and data file.
File → Write → Case & Data...
3.5. Summary
In this tutorial, you learned how to set up and solve a problem involving gas flow through porous media
in ANSYS Fluent. You also learned how to perform appropriate postprocessing. Flow non-uniformities
were easily identified through images of velocity vectors and pressure contours.
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Chapter 4: Modeling External Compressible Flow
This tutorial is divided into the following sections:
4.1. Introduction
4.2. Prerequisites
4.3. Problem Description
4.4. Setup and Solution
4.5. Summary
4.1. Introduction
Licensing Capability:
This tutorial is fully supported at all licensing levels.
The purpose of this tutorial is to compute the turbulent flow past a transonic wing at a nonzero angle
of attack. You will use the k-ω SST turbulence model.
This tutorial demonstrates how to do the following:
• Creation of capsule mesh using Watertight Geometry workflow.
• Model compressible flow (using the ideal gas law for density).
• Set boundary conditions for external aerodynamics.
• Use the k-ω SST turbulence model.
• Calculate a solution using the pressure-based coupled solver with the pseudo transient option.
• Check the near-wall mesh resolution by plotting the distribution of
.
Related video that demonstrates steps for setting up, solving, and postprocessing the solution results
for a turbulent flow within a manifold:
4.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
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Modeling External Compressible Flow
4.3. Problem Description
The problem considers the flow around a wing at an angle of attack α=3.06° and a free stream Mach
number of 0.8395 (M∞=0.8395). The flow is transonic, and has a shock near the mid-chord (x/c 0.20) on
the upper (suction) side. The wing has a mean aerodynamic chord length of 0.64607 m, a span of
1.1963 m, an aspect ratio of 3.8, and a taper ratio of 0.562. The geometry of the wing is shown in Figure 4.1: Problem Specification (p. 135).
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Setup and Solution
Figure 4.1: Problem Specification
4.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
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Modeling External Compressible Flow
4.4.1. Preparation
4.4.2. Meshing Workflow
4.4.3. Mesh
4.4.4. Solver
4.4.5. Models
4.4.6. Materials
4.4.7. Boundary Conditions
4.4.8. Operating Conditions
4.4.9. Reference Values
4.4.10. Solution
4.4.11. Postprocessing
4.4.1. Preparation
To prepare for running this tutorial:
1.
Download the external_compressible.zip file here.
2.
Unzip external_compressible.zip to your working directory.
The SpaceClaim CAD file wing.scdoc can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Meshing in the top-left selection list to start Fluent in Meshing Mode.
5.
Enable Double Precision under Options.
6.
Set Meshing Processes and Solver Processes to 4 under Parallel (Local Machine).
4.4.2. Meshing Workflow
1. Start the meshing workflow.
a. In the Workflow tab, select the Watertight Geometry workflow.
b. Review the tasks of the workflow.
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Setup and Solution
Each task is designated with an icon indicating its state (for example, as complete, incomplete, etc. For more information, see Understanding Task States in the Fluent User's Guide).
All tasks are initially incomplete and you proceed through the workflow completing all
tasks. Additional tasks are also available for the workflow. For more information, see
Customizing Workflows in the Fluent User's Guide.
2. Import the CAD geometry (wing.scdoc).
a. Select the Import Geometry task.
b. For Units, keep the default setting as mm.
c. For File Name, enter the path and file name for the CAD geometry that you want to import
(wing.scdoc).
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Modeling External Compressible Flow
Note:
The workflow only supports *.scdoc (SpaceClaim), Workbench (.agdb), and the
intermediary *.pmdb file formats.
d. Click Import Geometry.
This will update the task, display the geometry in the graphics window (Figure 3.2: The Imported
CAD Geometry for the Catalytic Converter (p. 90)), and allow you to proceed onto the next task in
the workflow.
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Setup and Solution
Figure 4.2: The Imported CAD Geometry for the Wing
The wing geometry has been encased in a half-spherical, half-cylindrical volume with 25m of space
in all directions.
Note:
Alternatively, you can use the ... button next to File Name to locate the CAD geometry file, after which, the Import Geometry task automatically updates, displaying
the geometry in the graphics window, and the workflow automatically progresses
to the next task.
Throughout the workflow, you are able to return to a task and change its settings using either the
Edit button, or the Revert and Edit button.
3. Add local sizing.
a. In the Add Local Sizing task, you are prompted as to whether or not you would like to add
local sizing controls to the faceted geometry.
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In this tutorial, we will add local sizing around the wing and a region past the trailing edge, since
they are areas where we require a more refined mesh. Later, we will apply settings for a coarser
surface mesh elsewhere.
i.
At the prompt for adding local sizing, select yes.
ii. Enter wing-facesize for the Name of the size control.
iii. Retain Face Size for the Size Control Type.
iv. Specify 10 for the Target Mesh Size.
v. Select wing_bottom and wing_top under Face Zone Labels.
b. Click Add Local Sizing task, you are prompted as to whether or not you would like to add
local sizing controls to the faceted geometry.
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Setup and Solution
You can now see the wing task in the workflow, which can be selected to change its settings. The
Add Local Sizing task can still be used to add more local sizing controls to the geometry.
i.
At the prompt for adding local sizing, select yes.
ii. Enter wing-edge-facesize for the Name of the size control.
iii. Retain Face Size for the Size Control Type.
iv. Specify 2 for the Target Mesh Size.
v. Select wing_edge under Face Zone Labels.
c. Click Add Local Sizing.
You can now see the wing task in the workflow, which can be selected to change its settings. The
Add Local Sizing task can still be used to add more local sizing controls to the geometry.
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i.
Enter wing-boi for the Name of the size control.
ii. Select Body Of Influence for the Size Control Type.
iii. Specify 5 for the Target Mesh Size.
iv. Select wing-boi under Face Zone Labels.
v. Click Add Local Sizing to complete this task and proceed to the next task in the workflow.
4. Generate the surface mesh.
a. In the Generate the Surface Mesh task, you can set various properties of the surface mesh
for the faceted geometry.
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Setup and Solution
b. Specify 2 for the Minimum Size.
c. Specify 1000 for the Maximum Size.
Note:
The red boxes displayed on the geometry in the graphics window are a graphical
representation of size settings. These boxes change size as the values change, and
they can be hidden by using the Clear Preview button.
d. Click Generate the Surface Mesh to complete this task and proceed to the next task in the
workflow.
5. Describe the geometry.
When you select the Describe Geometry task, you are prompted with questions relating to the
nature of the imported geometry.
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a. Select The geometry consists of only fluid regions with no voids option under Geometry Type, since this model contains only the fluid region.
b. Keep the rest of the default settings for this task.
c. Click Describe Geometry to complete this task and proceed to the next task in the
workflow.
6. Confirm and update the boundaries.
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Setup and Solution
a. Select the Update Boundaries task, where you can inspect the mesh boundaries and confirm
and change any designated boundaries accordingly. ANSYS Fluent attempts to determine the
correct arrangement of boundaries automatically.
b. All the proposed boundaries are correct, so click Update Boundaries. and proceed to the next
task.
7. Update your regions.
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a. Select the Update Regions task, where you can review and change the tabulated names and
types of the various regions that have been generated from your imported geometry, and
change them as needed.
We can see that the only defined region is the fluid region.
b. The proposed region type is correct, so click Update Regions to update your settings.
8. Add boundary layers.
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Setup and Solution
a. Select the Add Boundary Layers task, where you can set properties of the boundary layer
mesh.
For the Add Boundary Layers task, ensure yes is selected at the prompt as to whether or not
you want to define boundary layer settings. In this task, you can define specific details for
capturing the boundary layer in and around your geometry.
b. Specify 12 for Number of Layers.
Many boundary layers are desired to model a well resolved flow near the wall.
c. Click Add Boundary Layers.
9. Generating the volume mesh.
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a. Select the Generate the Volume Mesh task, where you can set properties of the volume mesh
itself.
b. Select the poly-hexcore for Fill With.
c. Specify 512 for Max Cell Length.
d. Enable Advanced Options to expose additional options that are required for this task.
Select yes for Check Self Proximity.
e. Click Generate the Volume Mesh.
ANSYS Fluent will apply your settings and proceed to generate a volume mesh for the wing geometry.. The mesh is displayed in the graphics window and a clipping plane is automatically inserted
with a layer of cells drawn so that you can quickly see the details of the volume mesh.
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Setup and Solution
10. Check the mesh.
Mesh → Check
11. Save the mesh file (wing.msh.gz).
File → Write → Mesh...
12. Switch to Solution mode.
Now that a mesh has been generated using ANSYS Fluent in meshing mode, you can now switch
to solver mode to complete the set up of the simulation. Note that to obtain more accurate
solutions a higher quality mesh should be used.
We have just checked the mesh, so select Yes when prompted to switch to solution mode.
4.4.3. Mesh
1. Examine the mesh (Figure 4.3: The Entire Mesh (p. 150) and Figure 4.4: Magnified View of the Mesh
Around the Wing (p. 151)).
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Figure 4.3: The Entire Mesh
To examine the cells of the mesh around the wing, display the mesh with edges enabled and the
far-field boundary disabled.
Domain → Mesh → Display...
a. Enable Edges in the Options group box.
b. Ensure All is selected in the Edge Type group box.
c. Deselect pressure-farfield from the Surfaces selection list.
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Setup and Solution
d. Click Display and close the Mesh Display dialog box.
e. Zoom in on the region around the wing, as shown in Figure 4.4: Magnified View of the Mesh
Around the Wing (p. 151).
Figure 4.4: Magnified View of the Mesh Around the Wing
The cells near the surface have a relativlely higher resolution and high aspect ratios, to account for
the flow around the wing.
Extra:
You can use the right mouse button to probe for mesh information in the graphics
window. If you click the right mouse button on any node in the mesh, information will
be displayed in the ANSYS Fluent console about the associated zone, including the
name of the zone. This feature is especially useful when you have several zones of the
same type and you want to distinguish between them quickly.
4.4.4. Solver
1. Set the solver settings.
Setup →
General
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a. Retain the default selection of Pressure-Based from the Type list.
The pressure-based solver with the Coupled option for the pressure-velocity coupling is a good
alternative to density-based solvers of ANSYS Fluent when dealing with applications involving highspeed aerodynamics with shocks. Selection of the coupled algorithm is made in the Solution
Methods task page in the Solution step.
4.4.5. Models
1. Select the k-ω SST turbulence model.
Physics → Models → Viscous...
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a. Retain the default selection of k-omega (2 eqn) in the Model list.
b. Retain the default selection of SST in the k-omega Model list.
c. Click OK to close the Viscous Model dialog box.
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4.4.6. Materials
The default Fluid Material is air, which is the working fluid in this problem. The default settings need to
be modified to account for compressibility and variations of the thermophysical properties with temperature.
1. Set the properties for air, the default fluid material.
Setup → Materials → Fluid → air
Edit...
a. Select ideal-gas from the Density drop-down list.
The Energy Equation will be enabled.
b. Select sutherland from the Viscosity drop-down list to open the Sutherland Law dialog box.
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i.
Retain the default selection of Three Coefficient Method in the Methods list.
ii. Click OK to close the Sutherland Law dialog box.
The Sutherland law for viscosity is well suited for high-speed compressible flows.
c. Click Change/Create to save these settings.
d. Close the Create/Edit Materials dialog box.
While Density and Viscosity have been made temperature-dependent, Cp (Specific Heat) and Thermal
Conductivity have been left constant. For high-speed compressible flows, thermal dependency of the
physical properties is generally recommended. For simplicity, Thermal Conductivity and Cp (Specific
Heat) are assumed to be constant in this tutorial.
4.4.7. Boundary Conditions
Setup →
Boundary Conditions
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1. Set the boundary conditions for pressure_farfield.
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Setup and Solution
Setup →
Boundary Conditions →
pressure_farfield → Edit...
a. Retain the default value of 0 Pa for Gauge Pressure.
Note:
The gauge pressure in ANSYS Fluent is always relative to the operating pressure,
which is defined in a separate input (see below).
b. Enter 0.8395 for Mach Number.
c. Enter 0.998574 and 0.053382 for the X-Component of Flow Direction and Z-Component
of Flow Direction, respectively.
These values are determined by the 3.06° angle of attack: cos 3.06° 0.998574 and sin 3.06° 0.053382
d. Retain Turbulent Viscosity Ratio from the Specification Method drop-down list in the Turbulence group box.
e. Retain the default value of 5% for Turbulent Intensity and 10 for Turbulent Viscosity Ratio.
The viscosity ratio should be between 1 and 10 for external flows.
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f.
Click the Thermal tab and enter 255.56 K for Temperature.
g. Click Apply and close the Pressure Far-Field dialog box.
4.4.8. Operating Conditions
1. Set the operating pressure.
Setup →
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Boundary Conditions → Operating Conditions...
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Setup and Solution
The Operating Conditions dialog box can also be accessed from the Cell Zone Conditions task page.
a. Enter 80600 Pa for Operating Pressure.
The operating pressure should be set to a meaningful mean value in order to avoid round-off errors.
The absolute pressure must be greater than zero for compressible flows. If you want to specify
boundary conditions in terms of absolute pressure, you can make the operating pressure zero.
b. Click OK to close the Operating Conditions dialog box.
For information about setting the operating pressure, see the Fluent User's Guide.
4.4.9. Reference Values
1. Set the reference values that are used to compute the pressure coefficient.
Setup →
Reference Values
The reference values are used to non-dimensionalize physical quantities used for postprocessing. The
dimensionless pressure coefficient will be used in future steps.
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a. Select pressure_farfield from the Compute from drop-down list.
ANSYS Fluent will update the Reference Values based on the boundary conditions at the far-field
boundary.
4.4.10. Solution
1. Set the solution parameters.
Solution → Solution → Methods...
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Retain the default settings.
2. Enable residual plotting during the calculation.
Solution → Reports → Residuals...
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a. Ensure that Plot is enabled in the Options group box and click OK to close the Residual
Monitors dialog box.
3. Initialize the solution.
Solution →
Initialization
a. Retain the default selection of Hybrid Initialization from the Initialization Methods group
box.
b. Click Initialize to initialize the solution.
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Setup and Solution
4. Save the case files (wing.cas.h5).
File → Write → Case...
5. Start the calculation by requesting 150 iterations.
Solution → Run Calculation → Run Calculation...
a. Enter 5 for the Time Scale Factor.
The Timescale Factor allows you to further manipulate the computed Time Step calculated by ANSYS
Fluent. Larger time steps can lead to faster convergence. However, if the time step is too large it
can lead to solution instability.
b. Enter 150 for Number of Iterations.
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c. Click Calculate.
6. Save the case and data files (wing.cas.h5 and wing.dat.h5).
File → Write → Case & Data...
4.4.11. Postprocessing
1. Plot the
distribution on the wing (Figure 4.5: Contour Plot of y+ Distribution (p. 165)).
Results → Graphics → Contours → New...
a. Enter contour-yplus for Contour Name.
b. Disable Node Values in the Options group box.
c. Select Turbulence... and Wall Yplus from the Contours of drop-down lists.
d. Select wing_bottom, wing_edge, and wing_top from the Surfaces selection list.
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e. Click Save/Display and close the Contours dialog box.
Note:
The values of
are dependent on the resolution of the mesh and the Reynolds number
of the flow, and are defined only in wall-adjacent cells. The value of
in the wall-adjacent cells dictates how wall shear stress is calculated.
The equation for
is
(4.1)
where is the distance from the wall to the cell center,
is the density of the air, and
is the wall shear stress.
is the molecular viscosity,
For this tutorial, the relatively coarse mesh was prepared with a target max value of
~100, as indicated in Figure 4.5: Contour Plot of y+ Distribution (p. 165).
Figure 4.5: Contour Plot of y+ Distribution
2. Plot the pressure distribution on the wing (Figure 4.6: Contour Plot of Pressure (p. 167) and Figure 4.7: Improved Contour Plot of Pressure (p. 169)).
Results → Graphics → Contours → New...
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a. Enter contour-pressure for Contour Name.
b. Enable Banded in the Coloring group box.
c. Select Pressure... and Static Pressure from the Contours of drop-down lists.
d. Select fluid_symmetry, wing_bottom, wing_edge, and wing_top from the Surfaces
selection list.
e. Click Save/Display.
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Figure 4.6: Contour Plot of Pressure
f.
To improve the visibility of the contour, click Colormap Options... to open the Colormap
dialog box.
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i.
Select bgr-pink from the Currently Defined drop-down list in the Colormap
group box.
ii. Click Apply and close the Colormap dialog box.
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Figure 4.7: Improved Contour Plot of Pressure
3. Create a plane near the shock region.
Results → Surface → Create → Plane...
a. Enter plane-zx for New Surface Name.
b. Select ZX Plane from the Method drop-down lists.
c. Enter 1.11 m for Y.
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This value corresponds to the y-coordinate at around the shock region near the tip of the wing.
Alternatively, you can click Select with Mouse to select a point from the graphics window.
d. Click Create and close the Plane Surface dialog box.
4. Plot the Mach number distribution on the wing near the shock region (Figure 4.8: Contour Plot of
Mach Number (p. 171)).
Results → Graphics → Contours → New...
a. Enter contour-mach for Contour Name.
b. Enable Banded in the Coloring group box.
c. Select Velocity... and Mach Number from the Contours of drop-down list.
d. Select plane-zx from the From Surface selection list.
e. Click Save/Display and close the Contours dialog box.
f.
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Zoom in on the region around the wing, as shown in Figure 4.8: Contour Plot of Mach Number (p. 171).
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Setup and Solution
Figure 4.8: Contour Plot of Mach Number
Note the discontinuity, in this case a shock, on the upper surface of the wing in Figure 4.8: Contour
Plot of Mach Number (p. 171) at about x/c 0.20.
5. Display filled contours of the
of Velocity (p. 173)).
component of velocity (Figure 4.9: Contour Plot of x Component
Results → Graphics → Contours → New...
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a. Enter contour-x-vel for Contour Name.
b. Ensure Filled is enabled in the Options group box.
c. Enable Banded in the Coloring group box.
d. Select Velocity... and X Velocity from the Contours of drop-down lists.
e. Select plane-zx from the From Surface selection list.
f.
Click Save/Display and close the Contours dialog box.
Note the flow reversal downstream of the shock in Figure 4.9: Contour Plot of x Component of Velocity (p. 173).
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Figure 4.9: Contour Plot of x Component of Velocity
6. Plot velocity vectors (Figure 4.10: Plot of Velocity Vectors Downstream of the Shock (p. 175)).
Results → Graphics → Vectors → New...
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a. Enter vector-vel for Vector Name.
b. Enter 0.05 for Scale.
c. Select Velocity... and X Velocity from the Color by drop-down lists.
d. Select plane-zx from the From Surface selection list.
e. Click Save/Display and close the Vectors dialog box.
f.
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Zoom in on the flow above the upper surface at a point downstream of the shock, as shown
in Figure 4.10: Plot of Velocity Vectors Downstream of the Shock (p. 175).
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Setup and Solution
Figure 4.10: Plot of Velocity Vectors Downstream of the Shock
Flow reversal is clearly visible in Figure 4.10: Plot of Velocity Vectors Downstream of the Shock (p. 175).
7. Create iso-surfaces near the shock region.
Results → Surface → Create → Iso-Surface...
a. Enter iso-y-bottom for New Surface Name.
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b. Select Mesh... and Y-Coordinate from the Surface of Constant drop-down lists.
c. Select wing_bottom from the From Surface selection list.
d. Click Compute and enter 1.11 m for Iso-Values.
This value corresponds to the y-coordinate at the shock region near the tip of the wing.
e. Click Create.
f.
Similarly, create a surface iso-y-top from the wing_top surface.
g. Close the Plane Surface dialog box.
8. Plot the component of wall shear stress on the wing near the shock region (Figure 4.11: XY Plot
of x Wall Shear Stress (p. 177)).
Results → Plots → XY Plot → New...
a. Enter xy-x-shear-stress for XY Plot Name.
b. Select Wall Fluxes... and X-Wall Shear Stress from the Y Axis Function drop-down lists.
c. Select iso-y-bottom and iso-y-top from the Surfaces selection list.
d. Click Save/Plot and close the Solution XY Plot dialog box.
As shown in Figure 4.11: XY Plot of x Wall Shear Stress (p. 177), the large, adverse pressure gradient induced by the shock causes the boundary layer to separate. The point of separation is where the wall
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Summary
shear stress vanishes. Flow reversal is indicated here by negative values of the x component of the wall
shear stress.
Figure 4.11: XY Plot of x Wall Shear Stress
9. Save the case file (wing.cas.h5).
File → Write → Case...
4.5. Summary
This tutorial demonstrated how to set up and solve an external aerodynamics problem using polyhexcore meshing, the pressure-based coupled solver with pseudo transient under-relaxation and the
k-ω SST turbulence model.
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Chapter 5: Fluid Flow and Heat Transfer in a Mixing
Elbow
This tutorial is divided into the following sections:
5.1. Introduction
5.2. Prerequisites
5.3. Problem Description
5.4. Setup and Solution
5.5. Summary
5.1. Introduction
This tutorial illustrates the setup and solution of a three-dimensional turbulent fluid flow and heat
transfer problem in a mixing elbow. The mixing elbow configuration is encountered in piping systems
in power plants and process industries. It is often important to predict the flow field and temperature
field in the area of the mixing region in order to properly design the junction.
This tutorial demonstrates how to do the following:
• Use the Watertight Geometry guided workflow to:
– Import a CAD geometry
– Generate a surface mesh
– Decribe the geometry
– Generate a volume mesh
• Launch ANSYS Fluent.
• Read an existing mesh file into ANSYS Fluent.
• Use mixed units to define the geometry and fluid properties.
• Set material properties and boundary conditions for a turbulent forced-convection problem.
• Create a surface report definition and use it as a convergence criterion.
• Calculate a solution using the pressure-based solver.
• Visually examine the flow and temperature fields using the postprocessing tools available in ANSYS
Fluent.
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• Change the solver method to coupled in order to increase the convergence speed.
• Adapt the mesh based on the temperature gradient to further improve the prediction of the temperature field.
5.2. Prerequisites
This tutorial assumes that you have little or no experience with ANSYS Fluent, and so each step will be
explicitly described.
5.3. Problem Description
The problem to be considered is shown schematically in Figure 5.1: Problem Specification (p. 181). A
cold fluid at 20° C flows into the pipe through a large inlet, and mixes with a warmer fluid at 40° C that
enters through a smaller inlet located at the elbow. The pipe dimensions are in inches and the fluid
properties and boundary conditions are given in SI units. The Reynolds number for the flow at the larger
inlet is 50,800, so a turbulent flow model will be required.
Note:
Since the geometry of the mixing elbow is symmetric, only half of the elbow must be modeled
in ANSYS Fluent.
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Setup and Solution
Figure 5.1: Problem Specification
5.4. Setup and Solution
To help you quickly identify graphical user interface items at a glance and guide you through the steps
of setting up and running your simulation, the ANSYS Fluent Tutorial Guide uses several type styles and
mini flow charts. See Typographical Conventions Used In This Manual (p. xxiii) for detailed information.
The following sections describe the setup and solution steps for running this tutorial in serial:
5.4.1. Preparation
5.4.2. Launching ANSYS Fluent
5.4.3. Meshing Workflow
5.4.4. Setting Up Domain
5.4.5. Setting Up Physics
5.4.6. Solving
5.4.7. Displaying the Preliminary Solution
5.4.8. Adapting the Mesh
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5.4.1. Preparation
1.
Download the introduction.zip file here.
2.
Unzip introduction.zip to your working directory.
3.
The SpaceClaim CAD file elbow.scdoc can be found in the folder. In addition, the elbow.pmdb
file is available for use on the Linux platform.
Note:
ANSYS Fluent tutorials are prepared using ANSYS Fluent on a Windows system. The screen
shots and graphic images in the tutorials may be slightly different than the appearance
on your system, depending on the operating system and/or graphics card.
5.4.2. Launching ANSYS Fluent
1. From the Windows Start menu, select Start > ANSYS 2021 R1 > Fluid Dynamics > Fluent 2021
R1 to start Fluent Launcher.
Fluent Launcher allows you to decide which version of ANSYS Fluent you will use, based on your
geometry and on your processing capabilities.
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Setup and Solution
2. Ensure that the proper options are enabled.
a. Ensure that the Double Precision option is selected.
b. Ensure that the Display Mesh After Reading option is enabled.
c. Set Processes to 4 under the Parallel (local Machine).
Note:
Fluent will retain your preferences for future sessions.
3. Set the working folder to the one created when you unzipped introduction.zip.
a. Click the Show More Options button to reveal additional options.
b. Enter the path to your working folder for Working Directory by double-clicking the text box
and typing.
Alternatively, you can click the browse button (
) next to the Working Directory text box
and browse to the directory, using the Browse For Folder dialog box.
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4. Click OK to launch ANSYS Fluent.
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Setup and Solution
5.4.3. Meshing Workflow
1. Start the meshing workflow.
a. In the Workflow tab, select the Watertight Geometry workflow.
b. Review the tasks of the workflow.
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Each task is designated with an icon indicating its state (for example, as complete, incomplete, etc. All tasks are initially incomplete and you proceed through the workflow completing all tasks. Additional tasks are also available for the workflow.
2. Import the CAD geometry (elbow.scdoc).
a. Select the Import Geometry task.
b. For Units, select in from the drop-down list.
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Setup and Solution
c. For File Name, enter the path and file name for the CAD geometry that you want to import
(elbow.scdoc).
Note:
The workflow only supports *.scdoc (SpaceClaim), Workbench (.agdb), and the
intermediary *.pmdb file formats.
d. Select Import Geometry.
This will update the task, display the geometry in the graphics window, and allow you to proceed
onto the next task in the workflow.
Note:
Alternatively, you can use the ... button next to File Name to locate the CAD geometry file, after which, the Import Geometry task automatically updates, displaying
the geometry in the graphics window, and the workflow automatically progresses
to the next task.
Throughout the workflow, you are able to return to a task and change its settings using either the
Edit button, or the Revert and Edit button.
3. Add local sizing.
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a. In the Add Local Sizing task, you are prompted as to whether or not you would like to add
local sizing controls to the faceted geometry.
b. For the purposes of this tutorial, you can keep the default setting of no.
c. Click Update to complete this task and proceed to the next task in the workflow.
4. Generate the surface mesh.
a. In the Generate the Surface Mesh task, you can set various properties of the surface mesh
for the faceted geometry.
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Setup and Solution
b. Specify 0.3 for Maximum Size.
Note:
The red boxes displayed on the geometry in the graphics window are a graphical
representation of size settings. These boxes change size as the values change, and
they can be hidden by using the Clear Preview button.
c. Click Generate the Surface Mesh to complete this task and proceed to the next task in the
workflow.
5. Describe the geometry.
When you select the Describe Geometry task, you are prompted with questions relating to the
nature of the imported geometry.
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a. Since the geometry defined the fluid region. Select The geometry consists of only fluid
regions with no voids for Geometry Type.
b. Click Describe Geometry to complete this task and proceed to the next task in the
workflow.
6. Update Boundaries Task
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a. For the Select Type field, select label.
b. For the wall-inlet boundary, change the Boundary Type field to wall.
c. Click Update Boundaries to complete this task and proceed to the next task in the workflow.
7. Update your regions.
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a. Select the Update Regions task, where you can review the names and types of the various
regions that have been generated from your imported geometry, and change them as needed.
b. Keep the default settings, and click Update Regions.
8. Add Boundary Layers.
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a. Select the Add Boundary Layers task, where you can set properties of the boundary layer
mesh.
b. Keep the default settings, and click Add Boundary Layers.
9. Generate the volume mesh.
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a. Select the Generate the Volume Mesh task, where you can set properties of the volume mesh.
b. Select the poly-hexcore for Fill With.
c. Specify 0.2614419 for Max Cell Length
d. Click Generate the Volume Mesh.
ANSYS Fluent will apply your settings and proceed to generate a volume mesh for the manifold
geometry. Once complete, the mesh is displayed in the graphics window and a clipping plane is
automatically inserted with a layer of cells drawn so that you can quickly see the details of the
volume mesh.
10. Check the mesh.
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Mesh → Check
11. Save the mesh file (elbow.msh.gz).
File → Write → Mesh...
12. Switch to Solution mode.
Now that a high-quality mesh has been generated using ANSYS Fluent in meshing mode, you can
now switch to solver mode to complete the set up of the simulation.
We have just checked the mesh, so select Yes when prompted to switch to solution mode.
5.4.4. Setting Up Domain
In this step, you will perform the mesh-related activities using the Domain ribbon tab (Mesh group
box).
1. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will report the results of the mesh check in the console.
Domain Extents:
x-coordinate: min (m) = -2.000000e-01, max (m) = 2.000000e-01
y-coordinate: min (m) = -2.250000e-01, max (m) = 2.000000e-01
z-coordinate: min (m) = 0.000000e+00, max (m) = 4.992264e-02
Volume statistics:
minimum volume (m3): 1.725403e-10
maximum volume (m3): 5.887684e-07
total volume (m3): 2.500657e-03
Face area statistics:
minimum face area (m2): 3.116238e-08
maximum face area (m2): 7.873458e-05
Checking mesh....................................
Done.
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The mesh check will list the minimum and maximum x, y, and z values from the mesh in the default
SI unit of meters. It will also report a number of other mesh features that are checked. Any errors
in the mesh will be reported at this time. Ensure that the minimum volume is not negative, since
ANSYS Fluent cannot begin a calculation when this is the case.
Note:
The minimum and maximum values may vary slightly when running on different platforms.
2. Set the working units for the mesh.
Domain → Mesh → Scale...
a. Select in from the View Length Unit In drop-down list to set inches as the working unit for
length.
b. Confirm that the domain extents are as shown in the previous dialog box.
c. Close the Scale Mesh dialog box.
The working unit for length has now been set to inches.
Note:
Because the default SI units will be used for everything except length, there is no need
to change any other units in this problem. The choice of inches for the unit of length
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has been made by the actions you have just taken. If you want a different working unit
for length, other than inches (for example, millimeters), click Units... in the Domain
ribbon tab (Mesh group box) and make the appropriate change in the Set Units dialog
box.
5.4.5. Setting Up Physics
In the steps that follow, you will select a solver and specify physical models, material properties, and
zone conditions for your simulation using the Physics ribbon tab.
1. In the Solver group box of the Physics ribbon tab, retain the default selection of the steady
pressure-based solver.
Physics → Solver → General
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2. Set up your models for the CFD simulation using the Models group box of the Physics ribbon
tab.
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Note:
You can also use the Models task page, which can be accessed from the tree by expanding Setup and double-clicking the Models tree item.
a. Enable heat transfer by activating the energy equation.
In the Physics ribbon tab, enable Energy (Models group box).
Physics → Models → Energy
Note:
You can also double-click the Setup/Models/Energy tree item and enable the energy
equation in the Energy dialog box.
b. Enable the -
turbulence model.
Physics → Models → Viscous...
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i.
Retain the default selection of k-omega from the Model list.
ii. Retain the default selection of SST in the k-omega Model group box.
iii. Click OK to accept all the other default settings and close the Viscous Model dialog box.
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Note that the Viscous... label in the ribbon is displayed in blue to indicate that the Viscous
model is enabled. Also Energy and Viscous appear as enabled under the Setup/Models
tree branch.
Note:
While the ribbon is the primary tool for setting up and solving your problem,
the tree is a dynamic representation of your case. The models, materials, conditions, and other settings that you have specified in your problem will appear in
the tree. Many of the frequently used ribbon items are also available via the
right-click functionality of the tree.
3. Set up the materials for the CFD simulation using the Materials group box of the Physics ribbon
tab.
Create a new material called water using the Create/Edit Materials dialog box.
a. In the Physics ribbon tab, click Create/Edit... (Materials group box).
Physics → Materials → Create/Edit...
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b. Click the Fluent Database... button to access pre-defined materials.
c. Select water-liquid (h2o < l >) from the Fluent Fluid Materials selection list and click Copy,
then close the Fluent Database Materials dialog box.
d. Ensure that there are now two materials (water-liquid and air) defined locally by examining
the Fluent Fluid Materials drop-down list.
Both the materials will also be listed under Fluid in the Materials task page and under the Materials tree branch.
e. Close the Create/Edit Materials dialog box.
4. Set up the cell zone conditions for the fluid zone (fluid) using the Zones group box of the Physics
ribbon tab.
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a. In the Physics tab, click Cell Zones (Zones group box).
Physics → Zones → Cell Zones
This opens the Cell Zone Conditions task page.
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b. Double-click fluid in the Zone list to open the Fluid dialog box.
Note:
You can also double-click the Setup/Cell Zone Conditions/fluid tree item in order
to open the corresponding dialog box.
c. Select water-liquid from the Material Name drop-down list.
d. Click Apply and close the Fluid dialog box.
5. Set up the boundary conditions for the inlets, outlet, and walls for your CFD analysis using the
Zones group box of the Physics ribbon tab.
a. In the Physics tab, click Boundaries (Zones group box).
Physics → Zones → Boundaries
This opens the Boundary Conditions task page where the boundaries defined in your simulation are displayed in the Zone selection list.
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Note:
To display boundary zones grouped by zone type (as shown previously), click the
Toggle Tree View button (
) in the upper right corner of the Boundary Conditions task page and select Zone Type under Group By.
Here the zones have names that were previously given during the meshing process. It is good
practice to give boundaries meaningful names in a meshing application to help when you set
up the model. You can also change boundary names in Fluent by simply editing the boundary
and making revisions in the Zone Name text box.
b. Set the boundary conditions at the cold inlet (cold-inlet).
Tip:
If you are unsure of which inlet zone corresponds to the cold inlet, you can
probe the mesh display using the right mouse button or the probe toolbar
button (
) as described previously in this tutorial. The information will be
displayed in the ANSYS Fluent console, and the zone you probed will be automatically selected from the Zone selection list in the Boundary Conditions
task page.
i.
Double-click cold-inlet to open the Velocity Inlet dialog box.
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ii. Retain the default selection of Magnitude, Normal to Boundary from the Velocity Specification Method drop-down list.
iii. Enter 0.4 [m/s] for Velocity Magnitude.
iv. In the Turbulence group box, select Intensity and Hydraulic Diameter from the Specification Method drop-down list.
v. Retain the default value of 5 [%] for Turbulent Intensity.
vi. Enter 4 [inches] for Hydraulic Diameter.
The hydraulic diameter
where
is defined as:
is the cross-sectional area and
is the wetted perimeter.
vii. Click the Thermal tab.
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viii.Enter 293.15 [K] for Temperature.
ix. Click Apply and close the Velocity Inlet dialog box.
Note:
You can also access the Velocity Inlet dialog box by double-clicking the
Setup/Boundary Conditions/cold-inlet tree item.
c. In a similar manner, set the boundary conditions at the hot inlet (hot-inlet), using the values
in the following table:
Setting
Value
Velocity Specification Method
Magnitude, Normal to Boundary
Velocity Magnitude
1.2 [m/s]
Specification Method
Intensity and Hydraulic Diameter
Turbulent Intensity
5 [%]
Hydraulic Diameter
1 [inch]
Temperature
313.15 [K]
d. Double-click outlet in the Zone selection list and set the boundary conditions at the outlet,
as shown in the following figure.
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Note:
• You do not need to set a backflow temperature in this case (in the Thermal tab)
because the material properties are not functions of temperature. If they were,
a flow-weighted average of the inlet conditions would be a good starting value.
• ANSYS Fluent will use the backflow conditions only if the fluid is flowing into the
computational domain through the outlet. Since backflow might occur at some
point during the solution procedure, you should set reasonable backflow conditions to prevent convergence from being adversely affected.
e. For the wall of the elbow (wall-elbow) and the wall of the hot inlet (wall-inlet), retain the
default value of 0 W/m2 for Heat Flux in the Thermal tab.
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5.4.6. Solving
In the steps that follow, you will set up and run the calculation using the Solution ribbon tab.
Note:
You can also use the task pages listed under the Solution tree branch to perform solutionrelated activities.
1. Select a solver scheme.
a. In the Solution ribbon tab, click Methods... (Solution group box).
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Solution → Solution → Methods...
Retain the default settings.
2. Enable the plotting of residuals during the calculation.
a. In the Solution ribbon tab, click Residuals... (Reports group box).
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Solution → Reports → Residuals...
Note:
You can also access the Residual Monitors dialog box by double-clicking the
Solution/Monitors/Residual tree item.
b. Ensure that Plot is enabled in the Options group box.
c. Retain the default value of 0.001 for the Absolute Criteria of continuity.
d. Click OK to close the Residual Monitors dialog box.
Note:
By default, the residuals of all of the equations solved for the physical models enabled
for your case will be monitored and checked by ANSYS Fluent as a means to determine
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the convergence of the solution. It is a good practice to also create and plot a surface
report definition that can help evaluate whether the solution is truly converged. You
will do this in the next step.
3. Create a surface report definition of average temperature at the outlet (outlet).
Solution → Reports → Definitions → New → Surface Report → Mass-Weighted Average...
Note:
You can also access the Surface Report Definition dialog box by right-clicking Report
Definitions in the tree (under Solution) and selecting New/Surface Report/MassWeighted Average... from the menu that opens.
a. Enter outlet-temp-avg for the Name of the report definition.
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b. Enable Report File, Report Plot, and Print to Console in the Create group box.
During a solution run, ANSYS Fluent will write solution convergence data in a report file, plot the
solution convergence history in a graphics window, and print the value of the report definition to
the console.
c. Set Frequency to 3 by clicking the up-arrow button.
This setting instructs ANSYS Fluent to update the plot of the surface report, write data to a file, and
print data in the console after every 3 iterations during the solution.
d. Select Temperature... and Static Temperature from the Field Variable drop-down lists.
e. Select outlet from the Surfaces selection list.
f.
Click OK to save the surface report definition and close the Surface Report Definition dialog
box.
The new surface report definition outlet-temp-avg will appear under the Solution/Report
Definitions tree item. ANSYS Fluent also automatically creates the following items:
• outlet-temp-avg-rfile (under the Solution/Monitors/Report Files tree branch)
• outlet-temp-avg-rplot (under the Solution/Monitors/Report Plots tree branch)
4. Examine the report file settings of the created report definition (outlet-temp-avg-rfile).
Solution → Monitors → Report Files → outlet-temp-avg-rfile
Edit...
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The Edit Report File dialog box is automatically populated with data from the outlet-temp-avg
report definition.
a. Verify that outlet-temp-avg is in the Selected Report Definitions list.
If you had created multiple report definitions, the additional ones would be listed under Available
Report Definitions , and you could use the Add>> and <<Remove buttons to manage which
were written in this particular report definition file.
b. (optional) Edit the name and location of the resulting file as necessary using the File Name
field or Browse... button.
c. Click OK to close the Edit Report File dialog box.
5. Create a convergence condition for outlet-temp-avg.
Solution → Reports → Convergence...
a. Click the Add button.
b. Enter con-outlet-temp-avg for Conditions.
c. Select outlet-temp-avg from the Report Definition drop-down list.
d. Enter 1e-5 for Stop Criterion.
e. Enter 20 for Ignore Iterations Before.
f.
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Enter 15 for Use Iterations.
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g. Enable Print.
h. Set Every Iteration to 3.
i.
Click OK to save the convergence condition settings and close the Convergence Conditions
dialog box.
These settings will cause Fluent to consider the solution converged when the surface report definition
value for each of the previous 15 iterations is within 0.001% of the current value. Convergence of the
values will be checked every 3 iterations. The first 20 iterations will be ignored, allowing for any initial
solution dynamics to settle out. Note that the value printed to the console is the deviation between
the current and previous iteration values only.
6. Initialize the flow field using the Initialization group box of the Solution ribbon tab.
Solution → Initialization
a. Retain the default selection of Hybrid from the Method list.
b. Click Initialize.
7. Save the case file (elbow1.cas.h5).
File → Write → Case...
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a. (optional) Indicate the folder in which you would like the file to be saved.
By default, the file will be saved in the folder from which you read in elbow.msh (that is, the
introduction folder). You can indicate a different folder by browsing to it or by creating a new
folder.
b. Enter elbow1.cas.h5 for Case File.
c. Ensure that the default Write Binary Files option is enabled, so that a binary file will be written.
d. Click OK to save the case file and close the Select File dialog box.
8. Start the calculation by requesting 150 iterations in the Solution ribbon tab (Run Calculation
group box).
Solution → Run Calculation
a. Enter 150 for No. of Iterations.
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b. Click Calculate.
Note:
By starting the calculation, you are also starting to save the surface report data at
the rate specified in the Surface Report Definition dialog box. If a file already exists
in your working directory with the name you specified in the Edit Report File dialog
box, then a Question dialog box will open, asking if you would like to append the
new data to the existing file. Click No in the Question dialog box, and then click
OK in the Warning dialog box that follows to overwrite the existing file.
As the calculation progresses, the surface report history will be plotted in the outlet-tempavg-rplot tab in the graphics window (Figure 5.2: Convergence History of the Mass-Weighted
Average Temperature (p. 217)).
Figure 5.2: Convergence History of the Mass-Weighted Average Temperature
Similarly, the residuals history will be plotted in the Scaled Residuals tab in the graphics
window (Figure 5.3: Residuals (p. 218)).
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Figure 5.3: Residuals
Note:
You can monitor the two convergence plots simultaneously by right-clicking a tab
in the graphics window and selecting SubWindow View from the menu that opens.
To return to a tabbed graphics window view, right-click a graphics window title
area and select Tabbed View.
Since the residual values vary slightly by platform, the plot that appears on your screen may
not be exactly the same as the one shown here.
The solution will be stopped by ANSYS Fluent when any of the following occur:
• the surface report definition converges to within the tolerance specified in the Convergence Conditions dialog box
• the residual monitors converge to within the tolerances specified in the Residual
Monitors dialog box
• the number of iterations you requested in the Run Calculation task page has been
reached
In this case, the solution is stopped when the convergence criterion on outlet temperature is
satisfied. The exact number of iterations for convergence will vary, depending on the platform
being used. An Information dialog box will open to alert you that the calculation is complete.
Click OK in the Information dialog box to proceed.
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9. Examine the plots for convergence (Figure 5.2: Convergence History of the Mass-Weighted Average
Temperature (p. 217) and Figure 5.3: Residuals (p. 218)).
Note:
There are no universal metrics for judging convergence. Residual definitions that are
useful for one class of problem are sometimes misleading for other classes of problems.
Therefore it is a good idea to judge convergence not only by examining residual levels,
but also by monitoring relevant integrated quantities and checking for mass and energy
balances.
There are three indicators that convergence has been reached:
• The residuals have decreased to a sufficient degree.
The solution has converged when the Convergence Criterion for each variable has
been reached. The default criterion is that each residual will be reduced to a value
of less than 10–3, except the energy residual, for which the default criterion is 10–6.
• The solution no longer changes with more iterations.
Sometimes the residuals may not fall below the convergence criterion set in the case
setup. However, monitoring the representative flow variables through iterations may
show that the residuals have stagnated and do not change with further iterations.
This could also be considered as convergence.
• The overall mass, momentum, energy, and scalar balances are obtained.
You can examine the overall mass, momentum, energy and scalar balances in the
Flux Reports dialog box. The net imbalance should be less than 0.2 % of the net
flux through the domain when the solution has converged. In the next step you will
check to see if the mass balance indicates convergence.
10. Examine the mass flux report for convergence using the Results ribbon tab.
Results → Reports → Fluxes...
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a. Ensure that Mass Flow Rate is selected from the Options list.
b. Select cold-inlet, hot-inlet, and outlet from the Boundaries selection list.
c. Click Compute.
The individual and net results of the computation will be displayed in the Results and Net Results
boxes, respectively, in the Flux Reports dialog box, as well as in the console.
The sum of the flux for the inlets should be very close to the sum of the flux for the outlets. The net
results show that the imbalance in this case is well below the 0.2% criterion suggested previously.
d. Close the Flux Reports dialog box.
11. Save the data file (elbow1.dat.h5).
File → Write → Data...
In later steps of this tutorial you will save additional case and data files with different suffixes.
5.4.7. Displaying the Preliminary Solution
In the steps that follow, you will visualize various aspects of the flow for the preliminary solution using
the Results ribbon tab.
1. Display filled contours of velocity magnitude on the symmetry plane (Figure 5.4: Predicted Velocity
Distribution after the Initial Calculation (p. 222)).
Results → Graphics → Contours → New...
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a. Enter contour-vel for Contour Name.
b. Ensure that Filled is enabled in the Options group box.
c. Ensure that Node Values and Boundary Values are enabled in the Options group box.
d. Select Banded in the Coloring group box.
e. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
f.
Select symmetry-xyplane from the Surfaces selection list.
g. Click Save/Display to display the contours in the active graphics window. Clicking the blue
z-axis arrow in the axis triad will orient the view with the z-axis, and clicking the Fit to Window
icon (
) will cause the object to fit exactly and be centered in the window.
Note:
If you cannot see the velocity contour display, select the appropriate tab in the
graphics window.
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h. Close the Contours dialog box.
View → Display
Disable the Headlight and Lighting options.
Figure 5.4: Predicted Velocity Distribution after the Initial Calculation
Extra:
When you probe a point in the displayed domain with the right mouse button or the
probe tool, the level of the corresponding contour is highlighted in the colormap in
the graphics window, and is also reported in the console.
2. Create and display a definition for temperature contours on the symmetry plane (Figure 5.5: Predicted Temperature Distribution after the Initial Calculation (p. 224)).
Results → Graphics → Contours → New...
You can create contour definitions and save them for later use.
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a. Enter contour-temp for Contour Name.
b. Select Temperature... and Static Temperature from the Contours of drop-down lists.
c. Select symmetry-xyplane from the Surfaces selection list.
d. Click Save/Display and close the Contours dialog box.
The new contour-temp definition appears under the Results/Graphics/Contours tree branch.
To edit your contour definition, right-click it and select Edit... from the menu that opens.
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Figure 5.5: Predicted Temperature Distribution after the Initial Calculation
3. Display velocity vectors on the symmetry plane (Figure 5.8: Magnified View of Resized Velocity
Vectors (p. 228)).
Results → Graphics → Vectors → New...
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a. Enter vector-vel for Vector Name.
b. Select arrow from the Style drop-down box.
c. Select symmetry-xyplane from the Surfaces selection list.
d. Click Save/Display to plot the velocity vectors.
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Figure 5.6: Velocity Vectors Colored by Velocity Magnitude
The Auto Scale option is enabled by default in the Options group box. This scaling sometimes
creates vectors that are too small or too large in the majority of the domain. You can improve
the clarity by adjusting the Scale and Skip settings, thereby changing the size and number
of the vectors when they are displayed.
e. Enter 4 for Scale.
f.
Set Skip to 2.
g. Click Save/Display again to redisplay the vectors.
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Figure 5.7: Resized Velocity Vectors
h. Close the Vectors dialog box.
i.
Zoom in on the vectors in the display.
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Figure 5.8: Magnified View of Resized Velocity Vectors
j.
Zoom out to the original view.
Clicking the Fit to Window icon,
the window.
, will cause the object to fit exactly and be centered in
4. Create a line at the centerline of the outlet. For this task, you will use the Surface group box of
the Results tab.
Results → Surface → Create → Iso-Surface...
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a. Enter z=0_outlet for New Surface Name.
b. Select Mesh... and Z-Coordinate from the Surface of Constant drop-down lists.
c. Click Compute to obtain the extent of the mesh in the z-direction.
The range of values in the z-direction is displayed in the Min and Max fields.
d. Retain the default value of 0 inches for Iso-Values.
e. Select outlet from the From Surface selection list.
f.
Click Create.
The new line surface representing the intersection of the plane z=0 and the surface outlet
is created, and its name z=0_outlet appears in the From Surface selection list.
Note:
• After the line surface z=0_outlet is created, a new entry will automatically be
generated for New Surface Name, in case you would like to create another surface.
• If you want to delete or otherwise manipulate any surfaces, click Manage... to
open the Surfaces dialog box.
g. Close the Iso-Surface dialog box.
5. Display and save an XY plot of the temperature profile across the centerline of the outlet for the
initial solution (Figure 5.9: Outlet Temperature Profile for the Initial Solution (p. 231)).
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Results → Plots → XY Plot → New...
a. Enter xy-outlet-temp for XY Plot Name.
b. Select Temperature... and Static Temperature from the Y Axis Function drop-down lists.
c. Select the z=0_outlet surface you just created from the Surfaces selection list.
d. Click Save/Plot.
e. Enable Write to File in the Options group box.
The button that was originally labeled Save/Plot will change to Write....
f.
Click Write....
i.
In the Select File dialog box, enter outlet_temp1.xy for XY File.
ii. Click OK to save the temperature data and close the Select File dialog box.
g. Close the Solution XY Plot dialog box.
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Figure 5.9: Outlet Temperature Profile for the Initial Solution
6. Define a custom field function for the dynamic head formula (
).
User Defined → Field Functions → Custom...
a. Select Density... and Density from the Field Functions drop-down lists, and click the Select
button to add density to the Definition field.
b. Click the X button to add the multiplication symbol to the Definition field.
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c. Select Velocity... and Velocity Magnitude from the Field Functions drop-down lists, and
click the Select button to add |V| to the Definition field.
d. Click y^x to raise the last entry in the Definition field to a power, and click 2 for the power.
e. Click the / button to add the division symbol to the Definition field, and then click 2.
f.
Enter dynamic-head for New Function Name.
g. Click Define and close the Custom Field Function Calculator dialog box.
The dynamic-head tree item will appear under the Parameters & Customization/Custom
Field Functions tree branch.
7. Display filled contours of the custom field function (Figure 5.10: Contours of the Dynamic Head
Custom Field Function (p. 233)).
Results → Graphics → Contours → New...
a. Enter contour-dynamic-head for Contour Name.
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b. Select Banded in the Coloring group box.
c. Select Custom Field Functions... and dynamic-head from the Contours of drop-down lists.
Tip:
Custom Field Functions... is at the top of the upper Contours of drop-down
list.
d. Select symmetry-xyplane from the Surfaces selection list.
e. Click Save/Display and close the Contours dialog box.
Figure 5.10: Contours of the Dynamic Head Custom Field Function
Note:
You may need to change the view by zooming out after the last vector display, if you
have not already done so.
8. Save the settings for the custom field function by writing the case and data files (elbow1.cas.h5
and elbow1.dat.h5).
File → Write → Case & Data...
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a. Ensure that elbow1.cas.h5 is entered for Case/Data File.
Note:
When you write the case and data file at the same time, it does not matter whether
you specify the file name with a .cas or .dat extension, as both will be saved.
b. Click OK to save the files and close the Select File dialog box.
c. Click OK to overwrite the files that you had saved earlier.
5.4.8. Adapting the Mesh
For the first run of this tutorial, you have solved the elbow problem using a fairly coarse mesh. The
elbow solution can be improved further by refining the mesh to better resolve the flow details. ANSYS
Fluent provides a built-in capability to easily adapt (locally refine) the mesh according to solution
gradients. In the following steps you will adapt the mesh based on the temperature gradients in the
current solution and compare the results with the previous results.
1. Define Cell Registers to Adapt the mesh in the regions of high temperature gradient.
Solution → Cell Registers
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a. Select Cells More Than from the Type drop-down list.
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b. Select Curvature from the Derivative Option drop-down list.
c. Select Temperature... and Static Temperature from the Curvature of drop-down list.
d. Click Compute.
ANSYS Fluent will update the Min and Max values to show the minimum and maximum temperature gradient.
e. Enter a value of 0.0015 for the Cells having value more than.
A general rule is to use about 10% of the maximum gradient when setting the value for refinement.
f.
Click Save and close the Field Variable Register daialog box.
2. Setup mesh adaption using the Cell Registers. For this task, you will use the Adapt group box
in the Domain ribbon tab.
Domain → Adapt → Refine / Coarsen...
a. Select the previously defined curvature_0 cell register from the Refinement Criterion dropdown lists.
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ANSYS Fluent will not coarsen beyond the original mesh for a 3D mesh. Hence, it is not necessary
to select the Coarsening Criterion in this instance.
b. Click Adapt.
c. Click Display.
ANSYS Fluent will display the cells marked for adaption in the graphics window (Figure 5.11: Cells
Marked for Adaption (p. 237)).
Figure 5.11: Cells Marked for Adaption
Extra
You can change the way ANSYS Fluent displays cells marked for adaption (Figure 5.12: Alternative Display of Cells Marked for Adaption (p. 239)) by performing the following steps:
i.
Click Display Options... in the Adaption Controls dialog box to open the Display
Options - Adaption dialog box.
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ii. Enable Draw Mesh in the Options group box.
The Mesh Display dialog box will open.
iii. Ensure that only the Edges option is enabled in the Options group box.
iv. Select Feature from the Edge Type list.
v. Select all of the items except z=0_outlet from the Surfaces selection list.
vi. Click Display and close the Mesh Display dialog box.
vii. Click OK to close the Display Options - Adaption dialog box.
viii.Click Display in the Adaption Controls dialog box.
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ix. Rotate the view and zoom in to get the display shown in Figure 5.12: Alternative
Display of Cells Marked for Adaption (p. 239).
Figure 5.12: Alternative Display of Cells Marked for Adaption
x. After viewing the marked cells, rotate the view back and zoom out again.
xi. Click OK to close the Adaption Controls dialog box.
3. Display the adapted mesh (Figure 5.13: The Adapted Mesh (p. 241)).
Domain → Mesh → Display...
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a. Disable Faces in the Options group box.
b. Select All from the Edge Type list.
c. Deselect all of the highlighted items from the Surfaces selection list except for symmetryxyplane.
Tip:
To deselect all surfaces, click the Deselect All Shown button (
) at the top of
the Surfaces selection list. Then select the desired surface from the Surfaces selection list.
d. Click Display and close the Mesh Display dialog box.
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Figure 5.13: The Adapted Mesh
4. Request an additional 150 iterations.
Solution → Run Calculation → Calculate
The solution will converge as shown in Figure 5.14: The Complete Residual History (p. 242) and Figure 5.15: Convergence History of Mass-Weighted Average Temperature (p. 242).
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Figure 5.14: The Complete Residual History
Figure 5.15: Convergence History of Mass-Weighted Average Temperature
5. Save the case and data files for the Coupled solver solution with an adapted mesh (elbow2.cas.h5 and elbow2.dat.h5).
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File → Write → Case & Data...
a. Enter elbow2.h5 for Case/Data File.
b. Click OK to save the files and close the Select File dialog box.
The files elbow2.cas.h5 and elbow2.dat.h5 will be saved in your default folder.
6. Display the temperature distribution (using node values) on the revised mesh using the temperature contours definition that you created earlier (Figure 5.16: Filled Contours of Temperature Using
the Adapted Mesh (p. 243)).
Right-click the Results/Graphics/Contours/contour-temp tree item and select Display from the
menu that opens.
Results → Graphics → Contours → contour-temp
Display
Figure 5.16: Filled Contours of Temperature Using the Adapted Mesh
7. Display and save an XY plot of the temperature profile across the centerline of the outlet for the
adapted solution (Figure 5.17: Outlet Temperature Profile for the Adapted Coupled Solver Solution (p. 244)).
Results → Plots → XY Plot → xy-outlet-temp
Edit...
a. Click Save/Plot to display the XY plot.
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Figure 5.17: Outlet Temperature Profile for the Adapted Coupled Solver Solution
b. Enable Write to File in the Options group box.
The button that was originally labeled Save/Plot will change to Write....
c. Click Write....
i.
In the Select File dialog box, enter outlet_temp2.xy for XY File.
ii. Click OK to save the temperature data.
d. Close the Solution XY Plot dialog box.
8. Display the outlet temperature profiles for both solutions on a single plot (Figure 5.18: Outlet
Temperature Profiles for the Two Solutions (p. 247)).
a. Open the Plot Data Sources dialog box.
Results → Plots → Data Sources...
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b. Click the Load File... button to open the Select File dialog box.
i.
Select outlet_temp1.xy and outlet_temp2.xy.
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Each of these files will be listed with their folder path in the bottom list to indicate that they
have been selected.
Tip:
If you select a file by mistake, simply click the file in the bottom list and
then click Remove.
ii. Click OK to save the files and close the Select File dialog box.
c. Select the folder path ending in outlet_temp1.xy from the Curve Information selection list
(Curves group box).
d. Enter Before Adaption in the lower-right text-entry box.
e. Click the Change Legend Entry button.
The item in the Legend Entries list for outlet_temp1.xy will be changed to Before Adaption. This
legend entry will be displayed in the upper-left corner of the XY plot generated in a later step.
f.
In a similar manner, change the legend entry for the folder path ending in outlet_temp2.xy
to be Adapted Mesh.
g. Click Plot and close the Plot Data Sources dialog box.
Figure 5.18: Outlet Temperature Profiles for the Two Solutions (p. 247) shows the two temperature profiles
at the centerline of the outlet. It is apparent by comparing both the shape of the profiles and the predicted outer wall temperature that the solution is highly dependent on the mesh and solution options.
Specifically, further mesh adaption should be used in order to obtain a solution that is independent
of the mesh.
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Summary
Figure 5.18: Outlet Temperature Profiles for the Two Solutions
5.5. Summary
A comparison of the convergence speed for the SIMPLE and Coupled pressure-velocity coupling schemes
indicates that the latter converges much faster. With more complex meshes, the difference in speed
between the two schemes can be significant.
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Chapter 6: Exhaust System: Fault-tolerant Meshing
This tutorial is divided into the following sections:
6.1. Introduction
6.2. Prerequisites
6.3. Problem Description
6.4. Setup and Solution
6.5. Summary
6.1. Introduction
This tutorial illustrates the setup and solution of a three-dimensional turbulent fluid flow in a manifold
exhaust system. The manifold configuration is encountered in the automotive industry. It is often important to predict the flow field in the area of the mixing region in order to properly design the junction.
You will use the Fault-tolerant Meshing guided workflow, which unlike the watertight workflow used
in Fluid Flow in an Exhaust Manifold (p. 1), is appropriate for geometries with imperfections, such as
gaps and leakages.
This tutorial demonstrates how to do the following in ANSYS Fluent:
• Use the Fault-tolerant Meshing guided workflow to:
– Import a CAD geometry and manage individual parts
– Generate a surface mesh
– Cap inlets and outlets
– Extract a fluid region
– Define leakages
– Extract edge features
– Setup size controls
– Generate a volume mesh
• Set up appropriate physics and boundary conditions.
• Calculate a solution.
• Review the results of the simulation.
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Related video that demonstrates steps for setting up, solving, and postprocessing the solution results
for a turbulent flow within a manifold:
6.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
6.3. Problem Description
The manifold modeled here is shown in Figure 6.1: Exhaust System Geometry for Flow Modeling (p. 250).
Air flows through the three inlets with a uniform velocity of 1 m/s, and then exits through the outlet.
Figure 6.1: Exhaust System Geometry for Flow Modeling
A small pipe is placed in the main portion of the manifold where edge extraction will be considered.
There is also a known small leakage included that will be addressed in the meshing portion of the tutorial to demonstrate the automatic leakage detection aspects of the meshing workflow.
6.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
6.4.1. Preparation
6.4.2. Geometry and Mesh
6.4.3. General Settings
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6.4.4. Solver Settings
6.4.5. Models
6.4.6. Materials
6.4.7. Cell Zone Conditions
6.4.8. Boundary Conditions
6.4.9. Solution
6.4.10. Postprocessing
6.4.1. Preparation
To prepare for running this tutorial:
1.
Download the exhaust_system.zip file here.
2.
Unzip exhaust_system.zip to your working directory.
The CAD file exhaust_system.fmd can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Meshing in the top-left selection list to start Fluent in Meshing Mode.
5.
Enable Double Precision under Options.
6.
Set Meshing Processes and Solver Processes to 4 under Parallel (Local Machine).
6.4.2. Geometry and Mesh
In this step, we will use ANSYS Fluent's guided workflow to import a CAD geometry, and perform
various enhancements so that we can generate a complete surface and volume mesh for a complete
CFD analysis.
1. Start the Fault-tolerant Meshing workflow.
a. In the Workflow tab, select the Fault-tolerant Meshing workflow.
b. Review the tasks of the workflow.
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Each task is designated with an icon indicating its state (for example, as complete, incomplete, etc. All tasks are initially incomplete and you proceed through the workflow completing all tasks. Additional tasks are also available for the workflow.
2. Import the CAD geometry (exhaust_system.fmd).
a. Select the Import CAD and Part Management task.
b. For CAD File, enter the path and file name for the CAD geometry that you want to import
(exhaust_system.fmd).
c. Perform some selective part management.
i.
Select Custom for Create Meshing Objects.
Using the Custom option allows you load the CAD objects, and selectively pick and choose
which parts you want to include in your CFD simulation as meshing objects. Selecting the One
per part option would load the CAD geometry and automatically create meshing objects for
every part.
ii. For Display Unit, keep the default setting as mm.
iii. Click the Load button.
This will load the CAD file's content into the CAD Model tree below.
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Setup and Solution
Note:
Items in the model trees that are checked indicate an object that is displayed
in the graphics window. Using the check boxes is not the same as selecting a
object in the tree to perform a particular operation.
Figure 6.2: Manifold CAD Geometry for Flow Modeling
iv. In the CAD Model tree, select the first part (main), hold the Shift button and select the
last part (object1), thereby selecting all of the parts.
You can also select the parts you require in the graphics window.
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v. Holding down the left mouse button, drag the collection of parts and drop them onto the
Meshing Model tree.
The parts in the CAD Model tree will become grayed out and will appear in the Meshing
Model tree. If you make a mistake, you can right-click the appropriate node in the Meshing
Model tree, and select the Restore to Cad Model option from the context menu, and the parts
will be restored to the CAD Model tree.
Note:
You can also select objects in the graphics window and add them to the tree.
Make sure that you select the check box for the top-level node in the Meshing Model tree to
view all of the parts of the meshing model in the graphics window.
vi. Select the top-level node in the Meshing Model tree and expand the Advanced Object
Settings list below the trees.
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Here, you can set specific properties on certain parts in the Meshing Model tree, such as
setting feature extraction angles and refaceting.
vii. For Create One Zone Per, select part.
viii.Click the Copy Settings to Child Objects button. This will apply your setting to all child
parts underneath the selected parent node in the tree.
d. Click Create Meshing Objects at the bottom of the task.
This will update the task, create meshing objects with the designated properties based on the selected portions of the CAD model. This will also display the geometry in the graphics window, and
allow you to proceed onto the next task in the workflow.
Throughout the workflow, you are able to return to a task and change its settings using either the
Edit button, or the Revert and Edit button.
3. Provide a description for the geometry and the flow characteristics.
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a. In the Describe Geometry and Flow task, you are prompted for more information about the
geometry and flow.
b. Select Internal flow through the object for the Flow Type.
c. Enable Advanced Options to expose additional options that are required for this task.
Many workflow tasks have advanced options that you may want to inspect before updating a task.
d. Select Yes for the Does your geometry require feature extraction? prompt.
This particular geometry has a few areas that will require special feature extraction treatment.
e. Click Describe Geometry and Flow to complete this task and proceed to the next task in the
workflow.
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4. Cover any openings in your geometry.
Select the Enclose Fluid Regions (Capping) task, where you can cover, or cap, any openings in
your geometry in order to later extract the enclosed fluid region.
a. Create a cap for one of the inlets.
i.
In the Name field, enter inlet-1 for the name of the capping surface to be applied
to one of the manifold's inlets.
ii. For the Zone Type field, choose velocity-inlet.
iii. For the Select By field, choose zone.
iv. In the list of zones, select inlet.1 as the opening that you want to cover.
For occasions when the list of items is long, you can use the Filter Text option and use
an expression such as in* to show only items starting with "in". Alternatively, you can
use the Use Wildcard option to list and pres-select matching items. See Filtering Lists and
Using Wildcards for more information.
The graphics window indicates the selected item.
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v. Click Create Cap(s) to complete this task and proceed to the next task in the workflow.
Once completed, this particular task will return you to a fresh task in order to assign
additional capping surfaces, if necessary. We will proceed to assign a cap for the remaining openings.
b. Repeat the previous steps, creating a cap called inlet-2 for the inlet.2 zone, and another
cap called inlet-3 for the inlet zone.
This will cover all of the manifold's inlets.
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Alternatively, you could also have selected all three inlet zones and created a single cap for all
three inlets.
c. Create a cap for the outlet.
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i.
In the Name field, enter outlet-1 for the name of the capping surface to be applied
to the manifold's outlet.
ii. For the Zone Type field, choose pressure-outlet.
iii. For the Select By field, specify zone.
iv. In the list of zones, select outlet for the outlet that you want to cover.
v. Click Create Cap(s) to complete this task.
Now, all of the openings in the geometry are covered.
5. Extract edge features.
In the Extract Edge Features task, you can set various properties for the extraction of features
in your geometry.
In this tutorial, we will create a single extraction object to capture the features between the smaller
pipe and the main manifold.
Create a feature extraction object based on intersection loops between the smaller pipe and the
main manifold.
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i.
Keep the default Name as edge-group-1
ii. Select Intersection Loops for the Extraction Method Using field.
iii. Select main and flow_pipe in the Objects list.
iv. Keep the default Intersected By setting as collectively.
This will localize the feature extraction to the intersection of the small pipe (flow_pipe)
with the main manifold (main).
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v. Click Extract Edge Features to complete this task and proceed to the next task in the
workflow.
6. Identify regions.
In the Identify Regions task, you can choose the various regions that you want to use in your
simulation.
In this tutorial, we will identify the internal fluid region as well as the external (void) region outside of
the geometry. The external void region will be useful in identifying any potential leakages from within
the fluid region to the outer domain.
a. Identify the fluid region.
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i.
For the Would you like to identify any fluid or void region(s)? prompt, keep the
default setting of yes.
ii. Keep the default Name as fluid-region-1
iii. Keep the default Define Location Using setting as Centroid of Objects.
iv. Keep the default Region Type setting as fluid.
v. Set the Select By setting to zone.
vi. Select main.1 in the list of zones.
vii. Click Identify Region.
Once completed, this particular task will return you to a fresh task in order to identify additional regions, if necessary. We will proceed to identify a void region.
b. Identify the region outside the geometry.
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i.
Change the Region Type setting to void.
ii. Keep the default Name as void-region-1
iii. Keep the default Define Location Using setting as Centroid of Objects.
iv. Keep the default Select By setting as object.
v. Select main, inlet-1, inlet-2, and inlet-3 in the list of objects.
This will ensure that the void region is located properly based on the centroid of the selected
objects.
vi. Click Identify Region to complete this task and proceed to the next task in the
workflow.
7. Define thresholds for any potential leakages.
In the Define Leakage Threshold task, you can choose to define a threshold for when leakages
within your geometry can be identified and automatically patched.
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a. Specify yes at the prompt to define a leakage threshold.
In the case of this tutorial, we know there is a potential leakage (a small opening in the main
manifold in the neck of the outlet) that we want to define a threshold.
b. Keep the default Name as leakage-1
c. Keep the default Select By: as identified region
d. Select void-region-1 from the Regions list.
e. Keep the default value of 6.4 mm for the Maximum Leakage Size.
f.
Click Preview Leakages.
This will display a cut plane through the domain that you can adjust using the Leakage Plane
controls. Use the Location slider and the Orientation fields to identify any potential leakages with
the current settings.
g. Adjust the Location slider to a value of 30 mm.
h. Change the Orientation setting to Y.
Rotate the display and examine the mesh. Note that there are no leakages present.
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i.
Click Define Leakage Threshold to complete this task and proceed to the next task in the
workflow.
8. Review your region settings.
a. In the Update Region Settings task, you can review and revise a table of settings for the
defined regions.
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b. For the Displayed Regions field, select Identified Regions, as a means of simplifying the
listing to only show previously identified regions.
c. For fluid-region-1, change the Volume Fill setting from hexcore to tet, since, for internal
flow, we are interested only in using tetrahedral cells.
To change the setting in the table, double-click the cell to expose the drop-down menu options.
d. Keep the Volume Fill setting for void-region-1 set to none.
This is done since we do not want to consider the void region, however, we want to use the Leakage
Size threshold of 6.4 mm to detect any leakages from the fluid region into the void region when
that threshold is exceeded.
e. Click Update Regions to complete this task and proceed to the next task in the workflow.
9. Select options for controlling the mesh.
In the Choose Mesh Control Options task, you can determine how much control you want when
generating the mesh: either through size controls; and/or through boundary layer settings.
For the purposes of this tutorial, you can keep the default settings in this task.
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Click Choose Options.
This will create a Add Local Sizing task.
a. For the Add Local Sizing task, keep the default size controls (default-curvature
and default-proximity) already populated with useful default settings.
10. Generate the surface mesh.
a. In the Generate the Surface Mesh task, you can customize how the surface mesh is created.
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b. Click Generate the Surface Mesh to complete this task and proceed to the next task in the
workflow.
ANSYS Fluent will apply your settings (calculate size fields, closing leakages, remeshing surfaces,
calculating regions, etc.) and proceed to generate a surface mesh for the manifold geometry. You
can visualize the surface mesh by selecting the Draw Mesh button at the bottom of the task, and
adjusting the clipping plane controls accordingly.
11. Confirm and update the boundaries.
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a. Select the Update Boundaries task, where you can inspect the mesh boundaries and confirm
and change any designated boundaries accordingly. ANSYS Fluent attempts to determine the
correct arrangement of boundaries automatically.
b. All the proposed boundaries are correct, so click Update Boundaries. and proceed to the next
task.
12. Add boundary layers.
For the Add Boundary Layers task, select yes at the prompt as to whether or not you want to
define boundary layer settings. In this task, you can define specific details for capturing the
boundary layer in and around your geometry.
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i.
Retain all defaults for this task.
These default settings create a continuous boundary layer along the walls of the fluid region.
ii. Click Add Boundary Layers to complete this task and proceed to the next task in the workflow.
13. Generate the volume mesh.
a. In the Generate the Volume Mesh task, you can customize how the volume mesh is created,
primarily defining the final skewness for the volume mesh.
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b. Select the Enable Region Settings to view and edit volume fill settings, prior to actually
generating the fluid volume mesh.
c. Click Generate the Volume Mesh to complete this task and proceed to the next task in the
workflow.
ANSYS Fluent will apply your settings and proceed to generate a volume mesh for the manifold
geometry. Once complete, the mesh is displayed in the graphics window and a clipping plane is
automatically inserted with a layer of cells drawn so that you can quickly see the details of the
volume mesh.
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14. Check the mesh.
Mesh → Check
15. Save the mesh file (exhaust_system.msh.gz).
File → Write → Mesh...
16. Switch to Solution mode.
Now that a high-quality mesh has been generated using ANSYS Fluent in meshing mode, you can
now switch to solver mode to complete the set up of the simulation.
We have just checked the mesh, so select Yes when prompted to switch to solution mode.
6.4.3. General Settings
In the Mesh group box of the Domain ribbon tab, set the units for length.
Domain → Mesh → Units...
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This opens the Set Units dialog box.
1. Select length under Quantities.
2. Select mm under Units.
3. Close the Set Units dialog box.
6.4.4. Solver Settings
In the Solver group box of the Physics ribbon tab, retain the default selection of the steady pressurebased solver.
Physics → Solver
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6.4.5. Models
1. Set up your models for the CFD simulation using the Models group box of the Physics ribbon
tab.
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Note:
You can also use the Models task page, which can be accessed from the tree by expanding Setup and double-clicking the Models tree item.
2. Retain the default k-ω SST turbulence model.
You will use the default settings for the k-ω SST turbulence model, so you can enable it directly from
the tree by right-clicking the Viscous node and choosing SST k-omega from the context menu.
Setup → Models → Viscous
Model → SST k-omega
6.4.6. Materials
Ordinarily, you would set up the materials for the CFD simulation using the Materials group box of
the Physics ribbon tab.
In this tutorial, we will keep the default fluid material of air.
6.4.7. Cell Zone Conditions
Ordinarily, you would set up the cell zone conditions for the CFD simulation using the Zones group
box of the Physics ribbon tab.
In this tutorial, we will keep the default assignment of air for the fluid zone.
6.4.8. Boundary Conditions
1. Set the velocity and turbulence boundary conditions for the first inlet (inlet-1).
Setup → Boundary Conditions → Inlet → inlet-1
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a. Enter 1 m/s for Velocity Magnitude.
b. Keep the remaining default settings.
c. Click Apply and close the Velocity Inlet dialog box.
2. Apply the same conditions for the other velocity inlet boundaries (inlet-2, and inlet-3).
3. Set the boundary conditions at the outlet (outlet-1).
Setup → Boundary Conditions → Outlet → outlet-1
Edit...
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a. Retain the default setting of 0 for Gauge Pressure.
b. Keep the remaining default settings.
c. Click Apply and close the Pressure Outlet dialog box.
4. Retain the remaining default (wall and interior) boundary conditions.
6.4.9. Solution
1. Specify the discretization schemes.
In the Solution ribbon tab, click Methods... (Solution group box).
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Solution → Solution → Methods...
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a. Retain the default settings for Solution Methods.
2. Monitor the mass flow rate at the inlets.
Solution → Reports → Definitions → New → Flux Report → Mass Flow Rate...
a. Enter mass-in for the Name of the report definition.
b. Ensure Mass Flow Rate is selected in the Options group box.
c. Select inlet-1, inlet-2, and inlet-3, from the Boundaries selection list.
d. Enable Report Plot and Print to Console in the Create group box.
e. Click OK to save the surface report definition and close the Flux Report Definition dialog
box.
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3. Monitor the total mass flow rate through the entire domain.
Perform the same procedure as described above, naming the report mass-tot, and selecting the
boundaries inlet-1, inlet-2, inlet-3, and outlet-1.
4. Monitor the mass balance.
Solution → Reports → Definitions → New → Expression...
a. Enter mass-bal for the Name of the expression.
b. Select mass-tot from the Report Definitions drop-down list on the right.
c. Type the / operand.
d. Select mass-in from the Report Definitions drop-down list on the right.
e. Enable Report Plot and Print to Console in the Create group box.
f.
Click OK to save the expression definition.
5. Initialize the flow field using the Initialization group box of the Solution ribbon tab.
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Solution → Initialization
a. Select Standard from the Method list.
b. Click Initialize.
6. Save the case file (exhaust_system.cas.h5).
File → Write → Case...
7. Start the calculation by requesting 100 iterations in the Solution ribbon tab (Run Calculation
group box).
Solution → Run Calculation
a. Enter 100 for No. of Iterations.
b. Click Calculate to begin the iterations.
As the solution progresses, the residuals history will be plotted in the Scaled Residuals tab
in the graphics window (Figure 6.3: Residuals (p. 283)).
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Figure 6.3: Residuals
c. Similarly, the monitors will be plotted in their respective tabs in the graphics window.
Figure 6.4: Mass Balance History
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The net mass imbalance is a small fraction (less than 0.5%) of the total mass flow rate through
the system, which indicates that the solution has converged.
8. Save the case and data files (exhaust_system.cas.h5 and exhaust_system.dat.h5).
File → Write → Case & Data...
6.4.10. Postprocessing
1. Display path lines highlighting the flow field (Figure 6.5: Pathlines Through the Manifold (p. 285)).
Results → Graphics → Pathlines → New...
a. Keep the default of pathlines-1 for the Name.
b. Select Particle Variables... and Time from the Color by drop-down lists.
c. Enable Accuracy Control under Options.
d. Set the Path Skip value to 5.
e. Select inlet-1, inlet-2, and inlet-3 from the Release from Surfaces list.
f.
Click Save/Display and close the Pathlines dialog box.
The new pathlines-1 definition appears under the Results/Graphics/Pathlines tree branch. To
edit your surface definition, right-click it and select Edit... from the menu that opens.
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Figure 6.5: Pathlines Through the Manifold
2. Create an iso-surface through the manifold geometry.
Results → Surface → New → Iso-Surface...
a. Select Mesh... and X-Coordinate from the Surface of Constant drop-down lists.
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b. Enter surf-x-coordinate for the Name.
c. Select fluid-region-1 from the From Zones list.
d. Click Compute.
e. Use the slider to locate the iso-surface in the middle of the geometry (approximately 380
mm).
f.
Click Create and close the Iso-Surface dialog box.
The new surf-x-coordinate definition appears under the Results/Surfaces tree branch. To edit
your surface definition, right-click it and select Edit... from the menu that opens.
3. Create and define contours of velocity magnitude throughout the manifold along with the mesh.
Results → Graphics → Contours → New...
a. Enter contour-velocity for the Name.
b. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
c. Select surf-x-coordinate from the Surfaces list.
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d. Disable Node Values under Options.
e. Disable Global Range under Options.
f.
Click Save/Display and close the Contours dialog box.
Figure 6.6: Contours of Velocity Magnitude Through the Manifold
4. Create a scene containing the mesh and the contours.
Results → Scene
New...
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a. Keep the default scene-1 for the Name and Title.
b. Select contour-velocity under Graphical Objects.
c. Create a new mesh object to add to the scene.
i.
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Click New Object and select Mesh to open the Mesh Display dialog box.
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ii. Select all of the surfaces under the Surfaces list, except the newly created surface.
iii. Click Save/Display and close the Mesh Display dialog box.
The new mesh-1 definition appears under the Results/Graphics/Mesh tree branch. The
new object also appears in the Scene dialog box.
d. In the Scene dialog box, set the Transparency to 90 for the mesh-1 graphical object.
e. Click Save & Display and close the Scene dialog box.
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Figure 6.7: Scene Containing the Mesh and Contours Throughout the Manifold
f.
Save the case file (exhaust_system.cas.h5).
File → Write → Case...
6.5. Summary
In this tutorial, you learned how to import a faulty CAD geometry, add modifications and enhancements,
generate a volume mesh, and set up, solve, and postprocess a CFD problem involving air flow through
a exhaust system.
Related video that demonstrates steps for setting up, solving, and postprocessing the solution results
for a turbulent flow within a manifold:
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Chapter 7: Modeling Hypersonic Flow
This tutorial is divided into the following sections:
7.1. Introduction
7.2. Prerequisites
7.3. Problem Description
7.4. Setup and Solution
7.5. Summary
7.1. Introduction
The purpose of this tutorial is to compute the flow around a re-entry capsule at hypersonic speed. The
simulated speed, trajectory, and ambient conditions are representative of such a vehicle as it passes
through the earth’s atmosphere at an altitude of approximately 50 [km].
This tutorial demonstrates how to do the following:
• Creation of capsule mesh using Watertight Geometry workflow.
• Model hypersonic flow, using high speed numerics, the two-temperature model for energy, and appropriate models for the properties of air.
• Set boundary conditions for external aerodynamics.
• Use the k-ω SST turbulence model.
• Calculate a solution using the density-based coupled solver.
7.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
7.3. Problem Description
The problem considers the flow around a re-entry capsule at an angle of attack α=-25° and a free stream
Mach number of 17.0. The geometry of the capsule is shown in Figure 7.1: Problem Specification (p. 292),
which also shows the lift and drag directions for the given case. The flow around the capsule can be
assumed to be symmetric for this tutorial.
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Figure 7.1: Problem Specification
7.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
7.4.1. Preparation
7.4.2. Meshing Workflow
7.4.3. Mesh
7.4.4. Solver
7.4.5. Models
7.4.6. Materials
7.4.7. Operating Conditions
7.4.8. Boundary Conditions
7.4.9. Solution
7.4.10. Postprocessing
7.4.1. Preparation
To prepare for running this tutorial:
1.
Download the reentry_capsule.zip file here.
2.
Unzip reentry_capsule.zip to your working directory.
The SpaceClaim CAD file CapsuleFlow.scdoc can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Meshing in the top-left selection list to start Fluent in Meshing Mode.
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5.
Enable Double Precision under Options.
6.
Set Meshing Processes and Solver Processes to 4 under Parallel (Local Machine).
7.4.2. Meshing Workflow
1. Start the meshing workflow.
a. In the Workflow tab, select the Watertight Geometry workflow.
b. Review the tasks of the workflow.
Each task is designated with an icon indicating its state (for example, as complete, incomplete, etc. For more information, see Understanding Task States in the Fluent User's Guide).
All tasks are initially incomplete and you proceed through the workflow completing all
tasks. Additional tasks are also available for the workflow. For more information, see
Customizing Workflows in the Fluent User's Guide.
2. Import the CAD geometry (reentry_capsule.zip).
a. Select the Import Geometry task.
b. For Units, select m.
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c. For File Name, enter the path and file name for the CAD geometry that you want to import
(CapsuleFlow.scdoc).
Note:
The workflow only supports *.scdoc (SpaceClaim), Workbench (.agdb), and the
intermediary *.pmdb file formats.
d. Click Import Geometry.
This will update the task, display the geometry in the graphics window and allow you to proceed
onto the next task in the workflow.
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Figure 7.2: The Imported CAD Geometry for the Capsule
The capsule geometry has been enclosed in a suitable flow domain, which should provide distinct
regions of inflow and outflow for a range of angles of attack, and avoids having the bow shock
that forms in such flows from contacting the inflow surfaces..
Note:
Alternatively, the ... button next to File Name can be used to locate the CAD geometry file, after which, the Import Geometry task automatically updates, displaying
the geometry in the graphics window, and the workflow automatically progresses
to the next task.
Throughout the workflow, you are able to return to a task and change its settings using either the
Edit button, or the Revert and Edit button.
3. Add local sizing.
Local mesh sizing controls are added on the wall surfaces using face sizing, and in the flow volume
around the capsule using Bodies Of Influence (BOIs), in regions of flow of interest. Note that all
the mesh sizes, local and global, are coarser than would be typical for industrial use, in order to
ensure the mesh is not too large for tutorial purposes.
a. In the Add Local Sizing task, add local sizing controls to the faceted geometry by selecting
yes:
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In this tutorial, we will add local sizing around the surfaces of the capsule, since they are areas
where we require a more refined mesh.
i.
At the prompt for adding local sizing, select yes.
ii. Enter capsule for the Name of the size control.
iii. Specify 1.1 for the Growth Rate.
iv. Retain Face Size for the Size Control Type.
v. Specify 0.1 for the Target Mesh Size.
vi. Select Zone for the Select By.
vii. Select origin-capsule.
b. Click Add Local Sizing.
In the Add Local Sizing task, you can add more local sizing controls to the faceted geometry.
Two bodies included in the geometry model are used for this purpose: one frustum-shaped
body to refine the flow region around and just downstream in the wake of the capsule, and
a second, toroidal body running along the sharp corner at the outer radius of the capsule.
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i.
Select Body Of Influence for the Size Control Type.
ii. Retain the default boi_1 for the Name of the size control.
iii. Specify 1.1 for the Growth Rate.
iv. Specify 0.2 for the Target Mesh Size.
v. Select Label for the Select By.
vi. Select capsuleflow-boi1.
c. Click Add Local Sizing.
The Add Local Sizing task can still be used to add more local sizing controls to the geometry.
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i.
Retain the default boi_2 for the Name of the size control.
ii. Specify 1.1 for the Growth Rate.
iii. Specify 0.05 for the Target Mesh Size.
iv. Select capsuleflow-boi2.
v. Click Add Local Sizing to complete this task and proceed to the next task in the workflow.
4. Generate the surface mesh.
With the local sizing set as described above, the global surface mesh sizing only defines the largest
elements on other surfaces, farther away from the capsule, on the inflow, outflow, and symmetry
surfaces.
a. In the Generate the Surface Mesh task, you can set various properties of the surface mesh
for the faceted geometry.
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b. Specify 0.1 for the Minimum Size.
c. Specify 1 for the Maximum Size.
Note:
The red boxes displayed on the geometry in the graphics window are a graphical
representation of size settings. These boxes change size as the values change, and
they can be hidden by using the Clear Preview button.
d. Specify 1.1 for the Growth Rate.
e. Click Generate the Surface Mesh to complete this task and proceed to the next task in the
workflow.
5. Describe the geometry.
When you select the Describe Geometry task, you are prompted with questions relating to the
nature of the imported geometry.
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a. Select The geometry consists of only fluid regions with no voids option under Geometry Type, since this model contains only the fluid region.
b. Keep the rest of the default settings for this task.
c. Click Describe Geometry to complete this task and proceed to the next task in the
workflow.
6. Confirm and update the boundaries.
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a. Select the Update Boundaries task, where you can inspect the mesh boundaries and confirm
and change any designated boundaries accordingly. ANSYS Fluent attempts to determine the
correct arrangement of boundaries automatically.
b. Select pressure-far-field for the inflow boundary.
c. Select pressure-outlet for the outflow boundary.
d. Select symmetry for the sym boundary.
e. All the proposed boundaries are correct, click Update Boundaries and proceed to the next
task.
7. Update your regions.
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a. Select the Update Regions task, where you can review and change the tabulated names and
types of the various regions that have been generated from your imported geometry and
change them as needed.
We can see that the only defined region is the fluid region.
b. The proposed region type is correct, so click Update Regions to update your settings.
8. Add boundary layers.
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a. Select the Add Boundary Layers task, where you can set properties of the boundary layer
mesh.
For the Add Boundary Layers task, ensure yes is selected at the prompt as to define boundary
layer settings. In this task, you can define specific details for capturing the boundary layer in
and around your geometry.
b. Select last-ratio for the Offset Method Type.
c. Retain the default last_ratio_1 for the Name of the size control.
d. Specify 30 for Number of Layers.
Many boundary layers are desired to model a well resolved flow near the wall.
e. Specify 1 for Transition Ratio.
f.
Specify 0.001 for First Height.
g. Click Add Boundary Layers.
9. Generating the volume mesh.
With the local sizing set as described above, including bodies of influence, the global volume
mesh sizing only defines the largest elements in the flow domain. In this case, the maximum is
set to be consistent with the specified global surface mesh sizing.
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a. Select the Generate the Volume Mesh task, to set properties of the volume mesh.
b. Select the polyhedra for Fill With.
c. Specify 1 for Max Cell Length.
d. Retain the default selection of Enable Parallel Meshing.
e. Click Generate the Volume Mesh.
ANSYS Fluent will apply your settings and proceed to generate a volume mesh for the wing geometry.. The mesh is displayed in the graphics window and a clipping plane is automatically inserted
with a layer of cells drawn so that you can quickly see the details of the volume mesh.
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Setup and Solution
10. Check the mesh.
Mesh → Check
11. Save the mesh file (CapsuleFlow.msh.gz).
File → Write → Mesh...
12. Switch to Solution mode.
Now that a mesh has been generated using ANSYS Fluent in meshing mode, you can now switch
to solver mode to complete the set up of the simulation. Note that to obtain more accurate
solutions a higher quality mesh should be used.
We have just checked the mesh, so select Yes when prompted to switch to solution mode.
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7.4.3. Mesh
1. To examine the cells of the mesh around the capsule display the mesh with edges and faces enabled and the far-field boundary disabled.
Domain → Mesh → Display...
a. Enable Edges in the Options group box.
b. Ensure All is selected in the Edge Type group box.
c. Select capsule and sym from the Surfaces selection list.
d. Click Display and close the Mesh Display dialog box.
e. Zoom in on the region around the capsule, as shown.
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Figure 7.3: View of the Mesh Around the Capsule
The cells near the surface have a relativlely higher resolution and high aspect ratios, to account for
the flow around the capsule.
7.4.4. Solver
1. Set the solver settings.
Setup →
General
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a. Select Density-Based from the Type group box.
7.4.5. Models
1. Select to solve the Energy Equation and with it the Two-Temperature Model option. In the twotemperature model, one temperature is representative of the translational and rotational energy
of the air molecules, and the other of their vibrational and electronic energy. Accounting for this
thermal non-equilibrium is important for accurate simulations of hypersonic flows, most importantly
in the predictions of surface heat transfer and temperatures.
Setup → Models → Energy Edit...
a. Select the Two-Temperature Model in the Energy Modes group box.
b. Click OK to close the Energy dialog box.
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2. Retain the default k-ω SST turbulence model.
You will use the default settings for the k-ω SST turbulence model, so you can enable it directly from
the tree by right-clicking the Viscous node and choosing SST k-omega from the context menu.
Setup → Models → Viscous
Model → SST k-omega
a. Ensure that Compressibilty Effects is selected in the Options group box.
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b. Click OK to close the Viscous model dialog box.
7.4.6. Materials
The default Fluid Material is air, which is the working fluid in this problem. For hypersonic flows it is important to account for compressibility and variations of the thermophysical properties with temperature.
This is done automatically when selecting to use the two-temperature model, to ensure that appropriate
properties are used.
1. Set the properties for air, the default fluid material.
Setup → Materials → Fluid → air
Edit...
Retain the default properties for air that are set automatically in conjunction with the selection
of the Two-temperature Model:
a. ideal-gas for Density.
b. Boltzmann-kinetic-theory for Specific Heat.
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c. eucken-relation for Thermal Conductivity.
d. blottner-curve-fit for Viscosity.
e. Close the Create/Edit Materials dialog box.
7.4.7. Operating Conditions
1. Set the operating pressure.
Setup →
Boundary Conditions → Operating Conditions...
The Operating Conditions dialog box can also be accessed from the Cell Zone Conditions task page.
a. Enter 0 Pa for Operating Pressure.
b. Click OK to close the Operating Conditions dialog box.
For information about setting the operating pressure, see the Fluent User's Guide.
7.4.8. Boundary Conditions
Set the momentum and energy boundary conditions.
1. Set the boundary conditions for far-field boundary.
Setup → Boundary Conditions → Inlet → inflow
Edit...
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a. Enter 25 Pa for Gauge Pressure.
b. Enter 17 for Mach Number.
c. Enter 0.90630778 and -0.42261826 for the X-Component of Flow Direction and YComponent of Flow Direction, respectively.
These values are determined by the -25° angle of attack: cos -25°= 0.90630778 and sin -25° = 0.42261826.
d. Retain Intensity and Viscosity Ratio from the Specification Method drop-down list in the
Turbulence group box.
e. Enter a value of 1% for Turbulent Intensity and 1 for Turbulent Viscosity Ratio.
f.
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Click the Thermal tab and enter 250 K for Temperature.
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g. Click Apply and close the Pressure Far-Field dialog box.
2. Set the boundary conditions for the outflow boundary.
Setup → Boundary Conditions → outlet → outflow
Edit...
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a. Enter 25 Pa for Gauge Pressure.
b. Select Average Pressure Specification.
c. Select Weak for the Averaging Method.
d. Retain Intensity and Viscosity Ratio from the Specification Method drop-down list in the
Turbulence group box.
e. Retain the default value of 1% for Turbulent Intensity and 1 for Turbulent Viscosity Ratio.
f.
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Click the Thermal tab and enter 250 K for Temperature.
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g. Click Apply and close the Pressure Outlet dialog box.
3. Set the boundary conditions for capsule wall.
Setup → Boundary Conditions → Wall → capsule
Edit...
a. Click the Thermal tab and enter 1500 K for Temperature.
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b. Click Apply and close the Wall dialog box.
7.4.9. Solution
1. Turn on high speed numerics in the TUI.
a. Press Enter in the console to get the command prompt (>).
b. Enter the text commands as shown in the box:
/solve/set/high-speed-numerics enable y
Enabling adaptive high-speed numerics for all Mach.
Reducing AMG termination criterion for flow (<0.01)
Activating divergence prevention
Activating limiter filter
Activating high-speed numerics
c. Enter the text commands as shown in the box:
/solve/set/cafsm y 100
2. Set the solution method parameters.
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Solution → Solution → Methods...
a. Retain the default Implicit for the Formulation drop-down list.
b. Select AUSM (Advection Upstream Splitting Method) from the Flux Type drop-down list.
c. Select Green-Gauss Node Based from the Gradient drop-down list in the Spatial Discretization group box.
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d. Select Second Order Upwind for Flow and Two-Temperature Model in the Spatial Discretization group box.
e. Select First Order Upwind for Turbulent Kinetic Energy and Specific Dissipation Rate in
the Spatial Discretization group box.
f.
Select Warped-Face Gradient Correction.
g. Select Higer Order Term Relaxation.
h. Select Convergence Acceleration For Stretched Meshes.
3. Set the solution control parameters.
Solution → Solution → Controls...
a. Click Limits... to open the Soluton Limits dialog box.
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b. Enter 20000 for the Maximum Static Temperature.
c. Click OK to close the Solution Limits dialog box.
4. Create a force report definition to plot and write the drag force on the capsule
Solution → Defnitions → New → Force Report → Drag...
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a. Enter drag-force for Name.
b. Select Drag Force in the Report Output Type group box.
c. Enter 0.9063078 for X and -0.4226183 for Y in the Force Vector group box.
d. Select capsule in the Zones selection list.
e. In the Create group box, enable Report Plot and Print to Console.
f.
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Click OK to close the Drag Report Definition dialog box.
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5. Similarly, create a force report definition for the lift force on the capsule.
Solution → Defnitions → Force Report → New → Lift...
a. Enter lift-force for Name.
b. Select Lift Force in the Report Output Type group box.
c. Enter 0.4226183 for X and 0.9063078 for Y in the Force Vector group box.
d. Select capsule in the Zones selection list.
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e. In the Create group box, enable Report Plot and Print to Console.
f.
Click OK to close the Lift Report Definition dialog box.
6. Create a flux report definition for the total heat transfer on the capsule
Solution → Defnitions → New → Flux Report → Total Heat Transfer Rate...
a. Enter heat-flux for Name.
b. Select capsule in the Zones selection list.
c. In the Create group box, enable Report Plot and Print to Console.
d. Click OK to close the Flux Report Definition dialog box.
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7. Enable residual plotting during the calculation.
Solution → Reports → Residuals...
a. Select Advanced Options to open the panel.
b. Select Scale and Compute Local Scale in the Residual Values group box.
c. Select local scaling from the Reporting Option drop down list.
d. Select Absolute under Convergence Criterion.
e. Ensure that Plot is enabled in the Options group box and click OK to close the Residual
Monitors dialog box.
8. Initialize the solution.
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Solution →
Initialization
a. Select Standard Initialization from the Initialization Methods group box.
b. Select Inflow from the Compute From drop down list.
c. Click Initialize to initialize the solution.
d. Run the Full Multigrid (FMG) initialization.
FMG initialization often facilitates an easier start-up of a calculation, especially for hypersonic flows
in which extremely strong variations and gradients are present, and the initialized solution must
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adapt to reflect the given boundary conditions. Use of FMG initialization usually minimizes the
need for users to take other measures at start-up, such as gradually ramping up the CFL (Courant
Friedrichs Lewy) number, thereby reducing the number of iterations for convergence.
i.
Press Enter in the console to get the command prompt (>).
ii. Enter the text commands and input responses as shown in the boxes. Accept the default
values by pressing Enter when no input response is given:
solve/initialize/set-fmg-initialization
Customize your FMG initialization:
set the number of multigrid levels [5] 3
set FMG parameters on levels ..
residual reduction on level 1 is: [0.001]
number of cycles on level 1 is: [10] 200
residual reduction on level 2 is: [0.001]
number of cycles on level 2 is: [50] 400
residual reduction on level 3 [coarsest grid] is:
number of cycles on level 3 is: [100] 1000
[0.001]
Number of FMG (and FAS geometric multigrid) levels: 3
* FMG customization summary:
*
residual reduction on level 0 [finest grid] is: 0.001
*
number of cycles on level 0 is: 1
*
residual reduction on level 1 is: 0.001
*
number of cycles on level 1 is: 200
*
residual reduction on level 2 is: 0.001
*
number of cycles on level 2 is: 400
*
residual reduction on level 3 [coarsest grid] is: 0.001
*
number of cycles on level 3 is: 1000
* FMG customization complete
set FMG courant-number [0.75] 0.25
enable FMG verbose? [no] yes
solve/initialize/fmg-initialization
Enable FMG initialization? [no] yes
Note:
Whenever FMG initialization is performed, it is important to inspect the FMG initialized
flow field using the postprocessing tools of ANSYS Fluent. Monitoring the normalized
residuals, which are plotted in the console window, will give you an idea of the convergence of the FMG solver. You should notice that the value of the normalized residuals
decreases. For more information about FMG initialization, including convergence
strategies, see the Fluent User's Guide.
9. Save the case files (CapsuleFlow.cas.h5).
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File → Write → Case...
10. Start the calculation.
Solution → Run Calculation → Run Calculation...
a. Enter 500 for Number of Iterations.
b. Click Calculate.
11. Save the case and data files (CapsuleFlow.cas.h5 and CapsuleFlow.dat.h5).
File → Write → Case & Data...
7.4.10. Postprocessing
1. Plot the Mach number distribution on the symmetry plane. This is one way to get an overall picture
of the flow field and important flow features, such as the detached bow shock ahead of the capsule,
flow expansion around its outer edge, and the wake behind the capsule.
Results → Graphics → Contours → New...
a. Enter contour-mach-sym for Contour Name.
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b. Disable the Global Range option in the Options group box.
c. Select Velocity... and Mach Number from the Contours of drop-down lists.
d. Select sym from the Surfaces selection list.
e. Select Draw Mesh.
f.
On the Mesh Display dialog box that opens, select capsule from the Surfaces selection
list.
g. Select Edges from the Options group box.
h. Select capsule from the Surfaces selection list.
i.
Click Display and close the Mesh Display dialog box.
j.
Click Save/Display and close the Contours dialog box.
2. Plot the total surface heat flux distribution on the capsule surface. The heat flux distribution on
the surfaces shows which parts of the capsule are predicted to experience the greatest thermal
load and hence would need to be correspondingly protected thermally. Keep in mind that, by
convention, the heat flux out of the flow solution domain is negative, so the largest thermal loads
have a negative sign.
Results → Graphics → Contours → New...
a. Enter contour-heat-flux for Contour Name.
b. Disable the Global Range option in the Options group box.
c. Select Wall Fluxes... and Total Surface Heat Flux from the Contours of drop-down lists.
d. Select capsule from the Surfaces selection list.
e. Click Save/Display.
f.
Change the light orientation to better visulaize the capsule surface.
Graphics → Lights...
View →
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g. Enter -1 for X in the Direction. group box
h. Click Apply and close the Lights dialog box.
i.
Close the Contours dialog box.
j.
3. Plot the ratio of the Translational-Rotation Temperature to Vibrational-Electronic Temperature on
the symmetry plane. This gives an indication of regions of thermal non-equilibrium in the flow,
which can are accounted for with the two-temperature model.
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Parameters & Customization → Custom Field Functions
New...
a. Select Two Temperature Model... and Translational-Rotational Temperature from the
Field Functions drop-down lists in the Select Operand Field Functions from group box
b. Select / from the calculator.
c. Select Vibrational-Electronic Temperature from the Field Functions drop-down list in
the Select Operand Field Functions from group box
d. Enter ttr-over-tve for New Function Name.
e. Click Define and close the Custom Field Function Calculator dialog box.
Results → Graphics → Contours → New...
a. Enter contour-ttr-tve for Contour Name.
b. Disable the Global Range option in the Options group box.
c. Select Custom Field Functions... and ttr-over-tve from the Contours of drop-down lists.
d. Select sym from the Surfaces selection list.
e. Click Save/Display and close the Contours dialog box.
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f.
4. Another way to examine the thermal non-equilibrium is to define a line through the shock to the
surface of the capsule, along which to plot the two temperatures. We will define the line to be
approximately along a line representing the stagnation line, parallel to the trajectory of the capsule.
Results → Surface → Create → Line/Rake...
a. Enter stagnation-line for New Surface Name.
b. Enter the values for x0, x1, y0, y1, z0, and z1 as follows:
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End Points
Value
x0
0.949
y0
0.97
z0
0
x1
01.855
y1
0.547
z1
0.
c. Click Create and close the Line/Rake Surface dialog box.
5. Plot the Translational-Rotational Temperature and the Vibrational-Electronic Temperature on the
approximate stagnation line.
Results → Plots → XY Plot → New...
a. Enter ttr-stag-line for XY Plot Name.
b. Select Two Temperature Model... and Translational-Rotational Temperature from the Y
Axis Function drop-down lists.
c. Select stagnation-line from the Surfaces selection list.
d. Enable Write to File in the Options group box to save the radial velocity profile.
e. Click the Write... button to open the Select File dialog box.
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i.
Enter trt-stag-line.xy in the XY File text entry box and click OK.
Be sure to double check the location where the files are being saved to ensure they will be saved
where you intend.
f.
Similarly write an xy plot file for the Vibrational-Electronic Temperature along the stagnationline named tve-stag-line.xy.
g. Close the Solution XY Plot dialog box.
6. Compare the Translational-Rotational Temperature and the Vibrational-Electronic Temperature on
the approximate stagnation line.
a. Open the Plot Data Sources dialog box.
Results → Plots → Data Sources...
b. Click the Load File... button to open the Select File dialog box.
i.
Select trt-stag-line.xy and tve-stag-line.xy.
ii. Click OK to save the files and close the Select File dialog box.
c. Select the folder path ending in trt-stag-line.xy from the Curve Information selection list
(Curves group box).
d. Enter Translational-Rotational in the lower-right text-entry box.
e. Click the Change Legend Entry button.
The item in the Legend Entries list for trt-stag-line.xy will be changed to Translational-Rotational.
This legend entry will be displayed in the upper-left corner of the XY plot generated in a later step.
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f.
In a similar manner, change the legend entry for the folder path ending in tve-stag-line.xy
to be Vibrational-Electronic.
g. Enter Trt & Tve Temperature for the Title and Legend Label.
h. Click Axes... and set the Precision to 2 and close the Axes - Plot Data Sources dialogue box.
i.
Click Plot and close the Plot Data Sources dialog box.
7. Save the case file (CapsuleFlow.cas.h5).
File → Write → Case...
7.5. Summary
This tutorial demonstrated how to set up and solve the hypersonic flow around a re-entry capsule as
it passes through the upper atmosphere.
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Chapter 8: Modeling Transient Compressible Flow
This tutorial is divided into the following sections:
8.1. Introduction
8.2. Prerequisites
8.3. Problem Description
8.4. Setup and Solution
8.5. Summary
8.1. Introduction
In this tutorial, ANSYS Fluent’s density-based implicit solver is used to predict the time-dependent flow
through a two-dimensional nozzle. As an initial condition for the transient problem, a steady-state
solution is generated to provide the initial values for the mass flow rate at the nozzle exit.
This tutorial demonstrates how to do the following:
• Calculate a steady-state solution (using the density-based implicit solver) as an initial condition for a
transient flow prediction.
• Define a transient boundary condition using an expression.
• Use dynamic mesh adaption for both steady-state and transient flows.
• Calculate a transient solution using the second-order implicit transient formulation and the densitybased implicit solver.
• Create an animation of the transient flow using ANSYS Fluent’s transient solution animation feature.
8.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
8.3. Problem Description
The geometry to be considered in this tutorial is shown in Figure 8.1: Problem Specification (p. 336).
Flow through a simple nozzle is simulated as a 2D planar model. The nozzle has an inlet height of 0.2 m,
and the nozzle contours have a sinusoidal shape that produces a 20% reduction in flow area. Symmetry
allows only half of the nozzle to be modeled.
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Figure 8.1: Problem Specification
8.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
8.4.1. Preparation
8.4.2. Reading and Checking the Mesh
8.4.3. Solution
8.4.4. Models
8.4.5. Materials
8.4.6. Operating Conditions
8.4.7. Boundary Conditions
8.4.8. Solution: Steady Flow
8.4.9. Enabling Time Dependence and Setting Transient Conditions
8.4.10. Specifying Solution Parameters for Transient Flow and Solving
8.4.11. Saving and Postprocessing Time-Dependent Data Sets
8.4.1. Preparation
To prepare for running this tutorial:
1.
Download the unsteady_compressible.zip file here.
2.
Unzip unsteady_compressible.zip to your working directory.
The file nozzle.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
6.
Disable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
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8.4.2. Reading and Checking the Mesh
1. Read the mesh file nozzle.msh.
File → Read → Mesh...
The mesh for the half of the geometry is displayed in the graphics window.
2. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and will report the progress in the console. Ensure
that the reported minimum volume is a positive number.
3. Verify that the mesh size is correct.
Domain → Mesh → Scale
Close the Scale Mesh dialog box.
4. For convenience, change the unit of measurement for pressure.
The pressure for this problem is specified in atm, which is not the default unit in ANSYS Fluent. You
must redefine the pressure unit as atm.
Domain → Mesh → Units...
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a. Select pressure in the Quantities selection list.
Scroll down the list to find pressure.
b. Select atm in the Units selection list.
c. Close the Set Units dialog box.
5. Mirror the mesh across the centerline (Figure 8.2: 2D Nozzle Mesh Display with Mirroring (p. 339)).
View → Display → Views...
a. Select symmetry in the Mirror Planes selection list.
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b. Click Apply to refresh the display.
c. Close the Views dialog box.
Figure 8.2: 2D Nozzle Mesh Display with Mirroring
8.4.3. Solution
1. Select the solver settings.
Setup →
General → Density-Based
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a. Select Density-Based in the General task page (Solver group box, under Type).
The density-based implicit solver is the solver of choice for compressible, transonic flows without
significant regions of low-speed flow. In cases with significant low-speed flow regions, the pressurebased solver is preferred. Also, for transient cases with traveling shocks, the density-based explicit
solver with explicit time stepping may be the most efficient.
b. Retain the default selection of Steady from the Time list.
Note:
You will solve for the steady flow through the nozzle initially. In later steps, you will
use these initial results as a starting point for a transient calculation.
8.4.4. Models
1. Enable the energy equation.
Setup → Models → Energy
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Model → On
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2. Retain the default k-omega SST turbulence model.
Setup → Models → Viscous
Model → SST k-omega
8.4.5. Materials
1. Define the settings for air, the default fluid material.
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Setup →
Materials →
air → Create/Edit...
a. Select ideal-gas from the Density drop-down list in the Properties group box, so that the
ideal gas law is used to calculate density.
Note:
ANSYS Fluent automatically enables the solution of the energy equation when the
ideal gas law is used, in case you did not already enable it manually in the Energy
dialog box.
b. Retain the default values for all other properties.
c. Click the Change/Create button to save your change.
d. Close the Create/Edit Materials dialog box.
8.4.6. Operating Conditions
1. Define the operating pressure.
Physics → Solver → Operating Conditions...
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a. Enter 0 atm for Operating Pressure.
b. Click OK to close the Operating Conditions dialog box.
Since you have set the operating pressure to zero, you will specify the boundary condition inputs for
pressure in terms of absolute pressures when you define them in the next step. Boundary condition
inputs for pressure should always be relative to the value used for operating pressure.
8.4.7. Boundary Conditions
1. Define the boundary conditions for the nozzle inlet (inlet).
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Setup → Boundary Conditions → Inlet → inlet (pressure-inlet)
344
Edit...
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a. Enter 0.9 atm for Gauge Total Pressure.
b. Enter 0.7369 atm for Supersonic/Initial Gauge Pressure.
The inlet static pressure estimate is the mean pressure at the nozzle exit. This value will be used
during the solution initialization phase to provide a guess for the nozzle velocity.
c. Retain Intensity and Viscosity Ratio from the Specification Method drop-down list in the
Turbulence group box.
d. Enter 1.5% for Turbulent Intensity.
e. Retain the setting of 10 for Turbulent Viscosity Ratio.
f.
Click Apply and close the Pressure Inlet dialog box.
2. Define the boundary conditions for the nozzle exit (outlet).
Setup → Boundary Conditions → Outlet → outlet (pressure-outlet)
Edit...
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a. Enter 0.7369 atm for Gauge Pressure.
b. Retain Intensity and Viscosity Ratio from the Specification Method drop-down list in the
Turbulence group box.
c. Enter 1.5% for Backflow Turbulent Intensity.
d. Retain the setting of 10 for Backflow Turbulent Viscosity Ratio.
If substantial backflow occurs at the outlet, you may need to adjust the backflow values to levels
close to the actual exit conditions.
e. Click Apply and close the Pressure Outlet dialog box.
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8.4.8. Solution: Steady Flow
In this step, you will generate a steady-state flow solution that will be used as an initial condition for the
time-dependent solution.
1. Define the solution parameters.
Solution → Solution → Methods...
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a. Retain the default selection of Least Squares Cell Based from the Gradient drop-down list
in the Spatial Discretization group box.
2. Modify the Courant Number.
Solution → Controls → Controls...
a. Enter 50 for the Courant Number.
Note:
The default Courant number for the density-based implicit formulation is 5. For relatively simple problems, setting the Courant number to 10, 20, 100, or even higher
value may be suitable and produce fast and stable convergence. However, if you
encounter convergence difficulties at the startup of the simulation of a properly
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Setup and Solution
set up problem, then you should consider setting the Courant number to its default
value of 5. As the solution progresses, you can start to gradually increase the
Courant number until the final convergence is reached.
b. Retain the default values for the Under-Relaxation Factors.
3. Enable the plotting of residuals.
Solution → Reports → Residuals...
a. Ensure that Plot is enabled in the Options group box.
b. Enable Show Advanced Options and select none from the Convergence Criterion dropdown list.
c. Click OK to close the Residual Monitors dialog box.
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4. Create the surface report definition for mass flow rate at the flow exit.
Solution → Reports → Definitions → New → Surface Report → Mass Flow Rate...
a. Enter mass_flowrate_out for Name.
b. Select outlet in the Surfaces selection list.
c. In the Create group box, enable Report File, Report Plot and Print to Console.
Note:
When Report File is enabled in the Surface Report Definition dialog box, the mass
flow rate history will be written to a file. If you do not enable this option, the history
information will be lost when you exit ANSYS Fluent.
d. Click OK to close the Surface Report Definition dialog box.
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mass_flowrate_out-rplot and mass_flowrate_out-rfile are automatically generated by Fluent
and appear in the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report
Files, respectively).
e. Modify the output file name.
Solution → Monitors → Report Files → mass_flowrate_out-rfile
i.
Edit...
Enter noz_ss.out for Output File Base Name.
ii. Click OK to close the Edit Report File dialog box.
5. Save the case file (noz_ss.cas.h5).
File → Write → Case...
6. Initialize the solution.
Solution → Initialization
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a. Keep the Method at the default of Hybrid.
b. Click Initialize.
7. Set up gradient adaption for dynamic mesh refinement.
You will enable dynamic adaption so that the solver periodically refines the mesh in the vicinity of the
shocks as the iterations progress. The shocks are identified by their large pressure gradients.
Domain → Adapt → Refine / Coarsen...
a. Select New and Field Variable... from the Cell Registers drop-down list, so that you can set
up the refinement cell register.
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i.
Enter scaled_gradient_refn for the Name of this field variable register.
ii. Select Cells More Than from the Type drop-down list.
iii. Select Gradient from the Derivative Option drop-down list.
The mesh adaption criterion can either be the gradient or the curvature (second gradient). Because strong shocks occur inside the nozzle, the gradient is used as the adaption criterion.
iv. Select Scale by Global Average from the Scaling Option drop-down list.
v. Select Pressure... and Static Pressure from the Scaled Gradient of drop-down list.
vi. Click Compute.
ANSYS Fluent will update the Min and Max values to show the minimum and maximum pressure
gradient.
vii. Enter a value of 0.7 for the Cells having value more than field.
viii.Click Save.
ix. Click Close to close the Field Variable Register dialog box.
b. Select New and Field Variable... from the Cell Registers drop-down list, so that you can set
up the coarsening cell register.
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i.
Enter scaled_gradient_crsn for the Name of this field variable register.
ii. Select Cells Less Than from the Type drop-down list.
iii. Select Gradient from the Deriviative Option drop-down list.
iv. Select Scale by Global Average from the Scaling Option drop-down list.
v. Select Pressure... and Static Pressure from the Curvature of drop-down list.
vi. Click Compute.
ANSYS Fluent will update the Min and Max values to show the minimum and maximum pressure
gradient.
vii. Enter a value of 0.3 for the Cells having value less than field.
viii.Click Save.
ix. Click Close to close the Field Variable Register dialog box.
c. Complete the setup in the Adaption Controls dialog box.
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i.
Select scaled_gradient_refn from the Refinement Criterion drop-down list.
ii. Select scaled_gradient_crsn from the Coarsening Criterion drop-down list.
iii. Enable Dynamic Adaption.
iv. Enter 100 for Frequency (iteration) of mesh adaption.
v. Click OK to close the Adaption Controls dialog box.
Info: The hanging node adaption method will not be available for 2D cases in a future release
of Fluent. The PUMA 2.5D adaption method can be used instead. To use PUMA 2.5D, convert
the 2D mesh to a 3D mesh with a thickness of one cell layer, and enter the following text
command: mesh/adapt/set/method puma-2.5d
vi. Click OK to close the Information dialog box.
8. Start the calculation by requesting 500 iterations.
Solution → Run Calculation → Run Calculation...
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a. Enter 500 for Number of Iterations.
b. Click Calculate to start the steady flow simulation.
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Figure 8.3: Mass Flow Rate History
9. Save the case and data files (noz_ss.cas.h5 and noz_ss.dat.h5).
File → Write → Case & Data...
Note:
When you write the case and data files at the same time, it does not matter whether
you specify the file name with a .cas.h5 or .dat.h5 extension, as both will be
saved.
10. Click OK in the Question dialog box to overwrite the existing file.
11. Review a mesh that resulted from the dynamic adaption performed during the computation.
Results → Graphics → Mesh
New...
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a. Enter mesh-ss for Mesh Name.
b. Ensure that only the Edges option is enabled in the Options group box.
c. Select Feature from the Edge Type list.
d. Ensure that all of the items are selected from the Surfaces selection list.
e. Click Display and close the Mesh Display dialog box.
The mesh after adaption is displayed in the graphics window (Figure 8.4: 2D Nozzle Mesh after
Adaption (p. 359)).
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Figure 8.4: 2D Nozzle Mesh after Adaption
f.
Zoom in using the middle mouse button to view aspects of your mesh.
Notice that the cells in the regions of high pressure gradients have been refined.
12. Display the steady flow contours of static pressure (Figure 8.5: Contours of Static Pressure (Steady
Flow) (p. 361)).
Results → Graphics → Contours → New...
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a. Enter contour-pressure for Contour Name.
b. Enable Banded in the Coloring group box.
c. Click Save/Display and close the Contours dialog box.
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Figure 8.5: Contours of Static Pressure (Steady Flow)
The steady flow prediction in Figure 8.5: Contours of Static Pressure (Steady Flow) (p. 361) shows the
expected pressure distribution, with low pressure near the nozzle throat.
13. Display the steady-flow velocity vectors (Figure 8.6: Velocity Vectors Showing Recirculation (Steady
Flow) (p. 363)).
Results → Graphics → Vectors → New...
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a. Enter vector-vel for Vector Name.
b. Select arrow from the Style drop-down list.
c. Enter 2 under Scale.
d. Click Save/Display and close the Vectors dialog box.
The steady flow prediction shows the expected form, with a peak velocity of approximately 300 m/s
through the nozzle.
You can zoom in on the wall in the expansion region of the nozzle to view the recirculation of the
flow as shown in Figure 8.6: Velocity Vectors Showing Recirculation (Steady Flow) (p. 363) .
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Figure 8.6: Velocity Vectors Showing Recirculation (Steady Flow)
14. Check the mass flux balance.
Important:
Although the mass flow rate history indicates that the solution is converged, you should
also check the mass flux throughout the domain to ensure that mass is being conserved.
Results → Reports → Fluxes...
a. Retain the default selection of Mass Flow Rate.
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b. Select inlet and outlet in the Boundaries selection list.
c. Click Compute and examine the values displayed in the dialog box.
Important:
The net mass imbalance should be a small fraction (for example, 0.1%) of the
total flux through the system. The imbalance is displayed in the lower right
field under Net Results. If a significant imbalance occurs, you should decrease
your residual tolerances by at least an order of magnitude and continue iterating.
d. Close the Flux Reports dialog box.
8.4.9. Enabling Time Dependence and Setting Transient Conditions
In this step you will define a transient flow by specifying a transient pressure condition for the nozzle.
1. Enable a time-dependent flow calculation.
Setup →
General
Select Transient in the General task page (Solver group box, under Time).
2. The pressure at the outlet is defined as a wave-shaped profile, and is described by the following
equation:
(8.1)
where
= circular frequency of transient pressure (rad/s)
= mean exit pressure (atm)
In this case,
per atm..
rad/s, and
atm.. To convert to SI units multiple by 101325 Pa
3. Define the transient boundary conditions at the nozzle exit (outlet).
Setup → Boundary Conditions → Outlet → outlet
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Setup and Solution
a. Select Expressions from Gauge Pressure drop-down list.
Enter the following expression for the outlet pressure as a function of time.
(0.12*sin(2200[Hz]*t)+0.737)*101325.0[Pa]
b. Click OK to close the Pressure Outlet dialog box.
4. Update the gradient adaption parameters for the transient case.
Domain → Adapt → Refine / Coarsen...
a. Enter 10 for Frequency (time-step) in the Dynamic Adaption group box.
For the transient case, the mesh adaption will be done every 10 time steps.
b. Click OK to close the Adaption Controls dialog box.
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8.4.10. Specifying Solution Parameters for Transient Flow and Solving
1. Modify the mass_flowrate_out-rfile report file definition.
Solution → Monitors → Report Files → mass_flowrate_out-rfile
Edit...
a. Enter noz_uns.out for Output File Base Name.
b. Select time-step from the Get Data Every drop-down list.
c. Click OK to close the Edit Report File dialog box.
2. Modify the mass_flowrate_out-rplot report plot definition.
Solution → Monitors → Report Plots → mass_flowrate_out-rplot
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a. For Get Data Every, retain the value of 1 and select time-step from the drop-down list.
Because each time step requires 10 iterations, a smoother plot will be generated by plotting at
every time step.
b. Select time-step from the X-Axis Label drop-down list.
c. Click OK to close the Edit Report File dialog box.
3. Save the transient solution case file (noz_uns.cas.h5).
File → Write → Case...
4. Modify the plotting of residuals.
Solution → Reports → Residuals...
a. Ensure that Plot is enabled in the Options group box.
b. Ensure none is selected from the Convergence Criterion drop-down list.
c. Set the Iterations to Plot to 100.
d. Click OK to close the Residual Monitors dialog box.
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Modeling Transient Compressible Flow
5. Define the time step parameters.
The selection of the time step is critical for accurate time-dependent flow predictions. Using a time
step of 2.85596 x 10-5 seconds, 100 time steps are required for one pressure cycle. The pressure cycle
begins and ends with the initial pressure at the nozzle exit.
Solution → Run Calculation → Run Calculation...
a. Enter 2.85596e-5 s for Time Step Size.
b. Enter 600 for Number of Time Steps.
c. Enter 10 for Max Iterations/Time Step.
d. Click Calculate to start the transient simulation.
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By requesting 600 time steps, you are asking ANSYS Fluent to compute six pressure cycles. The mass
flow rate history is shown in Figure 8.7: Mass Flow Rate History (Transient Flow) (p. 369).
Figure 8.7: Mass Flow Rate History (Transient Flow)
6. Optionally, you can review the effect of dynamic mesh adaption performed during transient flow
computation as you did in steady-state flow case.
7. Save the transient case and data files (noz_uns.cas.h5 and noz_uns.dat.h5).
File → Write → Case & Data...
8.4.11. Saving and Postprocessing Time-Dependent Data Sets
At this point, the solution has reached a time-periodic state. To study how the flow changes within a single
pressure cycle, you will now continue the solution for 100 more time steps. You will use ANSYS Fluent’s
solution animation feature to save contour plots of pressure and Mach number at each time step, and the
autosave feature to save case and data files every 10 time steps. After the calculation is complete, you will
use the solution animation playback feature to view the animated pressure and Mach number plots over
time.
1. Request the saving of case and data files every 10 time steps.
Solution → Activities → Autosave...
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Modeling Transient Compressible Flow
a. Enter 10 for Save Data File Every.
b. Select Each Time for Save Associated Case Files.
c. Retain the default selection of time-step from the Append File Name with drop-down list.
d. Enter noz_anim for File Name.
When ANSYS Fluent saves a file, it will append the time step value to the file name prefix (
noz_anim ). The standard extensions ( .cas.h5 and .dat.h5 ) will also be appended. This
will yield file names of the form noz_anim-1-00640.cas.h5 and noz_anim-100640.dat.h5 , where 00640 is the time step number.
e. Click OK to close the Autosave dialog box.
Tip:
If you have constraints on disk space, you can restrict the number of files saved by
ANSYS Fluent by enabling the Retain Only the Most Recent Files option and setting
the Maximum Number of Data Files to a nonzero number.
2. Create an animation definition for the nozzle pressure contour plot.
Solution → Activities → Create → Solution Animations...
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Setup and Solution
a. Enter pressure for the Name.
b. Select Time Step for Record after every.
The default value of 1 in the integer number entry box instructs ANSYS Fluent to update the animation sequence at every time step.
c. Select In Memory from the Storage Type drop-down.
The In Memory option is acceptable for a small 2D case such as this. For larger 2D or 3D cases,
saving animation files with either the Metafile or PPM Image option is preferable, to avoid using
too much of your machine’s memory.
d. Click New Object and select Contours... from the drop-down list to open the associated dialog
box.
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i.
Select Pressure... and Static Pressure from the Contours of drop-down lists.
ii. Ensure that Filled is enabled in the Options group box.
iii. Disable Auto Range.
iv. Enter 0.25 atm for Min and 1.25 atm for Max.
v. Click Save/Display and close the Contours dialog box.
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vi. Figure 8.8: Pressure Contours at t=0.017136 s
e. Ensure contour-1 is selected in the Animation Object group box.
f.
Click OK to create the animation definition.
3. Create an animation definition for the Mach number contour plot.
Solution → Activities → Create → Solution Animations...
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Modeling Transient Compressible Flow
a. Enter mach-number for the Name.
b. Select Time Step for Record after every.
The default value of 1 in the integer number entry box instructs ANSYS Fluent to update the animation sequence at every time step.
c. Ensure that In Memory is selected from the Storage Type drop-down.
d. Click New Object and select Contours... from the drop-down list to open the associated dialog
box.
i.
Select Velocity... and Mach Number from the Contours of drop-down lists.
ii. Ensure that Filled is enabled in the Options group box.
iii. Disable Auto Range.
iv. Enter 0.00 for Min and 1.30 for Max.
v. Click Save/Display and close the Contours dialog box.
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vi. Figure 8.9: Mach Number Contours at t=0.017136 s
e. Ensure contour-2 is selected in the Animation Object group box.
f.
Click OK to create the animation definition.
4. Continue the calculation by requesting 100 time steps.
By requesting 100 time steps, you will march the solution through an additional 0.0028 seconds, or
roughly one pressure cycle.
With the autosave and animation features active (as defined previously), the case and data files will
be saved approximately every 0.00028 seconds of the solution time; animation files will be saved every
0.000028 seconds of the solution time.
Solution → Run Calculation → Run Calculation...
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Modeling Transient Compressible Flow
Enter 100 for Number of Time Steps and click Calculate.
When the calculation finishes, you will have ten pairs of case and data files and there will be 100 pairs
of contour plots stored in memory. In the next few steps, you will play back the animation sequences
and examine the results at several time steps after reading in pairs of newly saved case and data files.
5. Play the animation of the pressure contours.
Results → Animations → Solution Animation Playback
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a. Select pressure in the Sequences selection list.
b. Click the play button (the second from the right in the group of buttons in the Playback group
box).
c. Close the Playback dialog box.
Examples of pressure contours at
s (the 630th time step) and
s (the 670th
time step) are shown in Figure 8.10: Pressure Contours at t=0.017993 s (p. 378) and Figure 8.11: Pressure
Contours at t=0.019135 s (p. 378). These contour plots can be shown by selecting frame 30 and 70
in theFrame selector in the Playback dialog box.
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Modeling Transient Compressible Flow
Figure 8.10: Pressure Contours at t=0.017993 s
Figure 8.11: Pressure Contours at t=0.019135 s
6. In a similar manner to steps 4 and 5, select the appropriate active window and animation sequence
name for the Mach number contours.
Examples of Mach number contours at
s and
s are shown in Figure 8.12: Mach
Number Contours at t=0.017993 s (p. 379) and Figure 8.13: Mach Number Contours at
t=0.019135 s (p. 379).
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Setup and Solution
Figure 8.12: Mach Number Contours at t=0.017993 s
Figure 8.13: Mach Number Contours at t=0.019135 s
Tip:
ANSYS Fluent gives you the option of exporting an animation as an MPEG file or as a
series of files in any of the hardcopy formats available in the Save Picture dialog box
(including TIFF and PostScript).
To save an MPEG file, select MPEG from the Write/Record Format drop-down list in
the Playback dialog box and then click the Write button. The MPEG file will be saved
in your working folder. You can view the MPEG movie using an MPEG player (for example, Windows Media Player or another MPEG movie player).
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Modeling Transient Compressible Flow
To save a series of TIFF, PostScript, or other hardcopy files, select Picture Frames in
the Write/Record Format drop-down list in the Playback dialog box. Click the Picture
Options... button to open the Save Picture dialog box and set the appropriate parameters for saving the hardcopy files. Click Apply in the Save Picture dialog box to
save your modified settings. Click Save... to select a directory in which to save the files.
In the Playback dialog box, click the Write button. ANSYS Fluent will replay the animation, saving each frame to a separate file in your working folder.
If you want to view the solution animation in a later ANSYS Fluent session, you can
select Animation Frames as the Write/Record Format and click Write.
Warning:
Because the solution animation was stored in memory, it will be lost if you exit
ANSYS Fluent without saving it in one of the formats described previously. Note
that only the animation-frame format can be read back into the Playback dialog
box for display in a later ANSYS Fluent session.
7. Read the case and data files for the 660th time step (noz_anim–1–00660.cas.h5 and
noz_anim–1–00660.dat.h5) into ANSYS Fluent.
8. Plot vectors at
s (p. 382)).
s (the 660th time step) (Figure 8.14: Velocity Vectors at t=0.018849
Results → Graphics → Vectors → New...
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Setup and Solution
a. Enter velocity-vel-660 for Vector Name
b. Ensure Auto Scale is enabled under Options.
c. Select arrow from the Style drop-down list.
d. Enter 10 under Scale.
e. Enter 50 under Skip.
f.
Click Save/Display and close the Vectors dialog box.
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Modeling Transient Compressible Flow
Figure 8.14: Velocity Vectors at t=0.018849 s
The transient flow prediction in Figure 8.14: Velocity Vectors at t=0.018849 s (p. 382) shows the expected
form, with peak velocity of approximately 260 m/s through the nozzle at
seconds.
9. Save the case file (noz_anim-1-00660.cas.h5).
File → Write → Case...
10. In a similar manner to steps 7 and 8, read the case and data files saved for other time steps of
interest and display the vectors.
8.5. Summary
In this tutorial, you modeled the transient flow of air through a nozzle. In doing so, you learned how
to:
• generate a steady-state solution as an initial condition for the transient case.
• set solution parameters for implicit time-stepping and apply a user-defined transient pressure
profile at the outlet.
• use mesh adaption to refine the mesh in areas with high pressure gradients to better capture
the shocks.
• automatically save solution information as the transient calculation proceeds.
• create and view solution animations of the transient flow.
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Chapter 9: Using the Frozen Rotor Method
This tutorial is divided into the following sections:
9.1. Introduction
9.2. Prerequisites
9.3. Problem Description
9.4. Setup and Solution
9.5. Summary
9.6. Further Improvements
9.1. Introduction
In this tutorial, you will setup a general fluid flow simulation to evaluate the performance of a centrifugal
pump with a vaneless volute using the Frozen Rotor method.
This tutorial demonstrates how to do the following:
• Set up a No Pitch-Scale interface using the turbo model.
• Describe wall motion and other boundary conditions.
• Specify appropriate solver settings.
• Add and monitor expressions.
• Calculate expressions and display contours.
9.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
9.3. Problem Description
The problem to be considered is the modeling of a centrifugal pump with a volute as shown in Figure 9.1: Case Geometry (p. 384). The pump impeller has 5 blades and rotates at a velocity of 1450 RPM.
The mass flow rate at the volute outlet is known to be 90 kg/s. A gauge total pressure of 0 pa is used
at the inlet. The simulation will be performed to determine the head generated by the pump, representing the overall pressure increase of the fluid.
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Using the Frozen Rotor Method
Figure 9.1: Case Geometry
9.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
9.4.1. Preparation
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Setup and Solution
9.4.2. Mesh
9.4.3. Models
9.4.4. Materials
9.4.5. Cell Zone Conditions
9.4.6. Boundary Conditions
9.4.7.Turbo Model
9.4.8. Solution
9.4.9. Postprocessing
9.4.1. Preparation
To prepare for running this tutorial:
1.
Download the pump_volute.zip file here.
2.
Unzip pump_volute.zip to your working directory.
The mesh file pump_volute.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 4 under Parallel (Local Machine).
9.4.2. Mesh
1. Read the mesh file pump_volute.msh.
File → Read → Mesh...
As Fluent reads the mesh file, it will report the progress in the console.
9.4.3. Models
1. Enable the -
SST turbulence model.
Physics → Models → Viscous...
a. Retain the default k-omega SST turbulence model.
b. Click OK.
Compared to other two-equation models, the - SST turbulence model effectively predicts flow separation in turbomachinery, allowing for accurate evaluation of pump performance.
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9.4.4. Materials
1. Add water to the list of materials.
Physics → Materials → Create/Edit...
a. Click Fluent Database... to open the Fluent Database Materials dialog box.
b. Scroll down and select water-liquid (h2o <l>) from the list of materials.
c. Select Copy.
d. Close the Fluent Database Materials dialog box and the Create/Edit Materials dialog box.
water-liquid appears under Materials > Fluid in the tree view.
9.4.5. Cell Zone Conditions
1. Set the cell zone conditions for the impeller.
Setup → Cell Zone Conditions → Fluid → impeller
Edit...
a. Set the Material Name to water-liquid.
b. Select Frame Motion.
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c. Ensure values of (0, 0, 1) for X, Y, and Z in the Rotation-Axis Direction group box.
The impeller will rotate relative to the absolute frame. By default, the correct rotation is set (about
the z-axis).
d. For Rotational Velocity > Speed (rpm), specify 1450.
e. Click Apply and close the Fluid dialog box .
2. Set the cell zone conditions for the volute.
Setup → Cell Zone Conditions → Fluid → volute
Edit...
a. Set the Material Name to water-liquid.
The volute is stationary in the absolute frame so no motion is required.
b. Ensure values of (0, 0, 1) for X, Y, and Z in the Rotation-Axis Direction group box.
c. Click Apply and close the Fluid dialog box.
9.4.6. Boundary Conditions
1. Set the boundary conditions for impeller-hub.
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Setup → Boundary Conditions → Wall → impeller-hub
Tab
Momentum
Setting
Edit...
Value
Wall Motion
Moving Wall
Motion
Rotational
By default, the rotating wall is specified with a velocity of 0 relative to the impeller fluid zone.
2. Set the boundary conditions for inblock-shroud.
Setup → Boundary Conditions → Wall → inblock-shroud
Tab
Momentum
Setting
Edit...
Value
Wall Motion
Moving Wall
Motion
Absolute
Motion
Rotational
The inblock shroud wall is stationary (velocity equal to 0) relative to the absolute reference frame.
3. Set the boundary conditions for the inlet.
Setup → Boundary Conditions → Inlet → inlet
Tab
Momentum
Edit...
Setting
Supersonic/Initial Gauge
Pressure
Value
-100
(pascal)
4. Set the boundary conditions for the outlet.
The outlet has been automatically set as an inlet by Fluent. You must first change this boundary
condition to a mass flow outlet.
Setup → Boundary Conditions → Inlet → mass-flow-inlet-11
Setup → Boundary Conditions → Outlet → mass-flow-outlet-11
Tab
Momentum
Setting
Mass Flow Rate
Type → mass-flow-outlet
Edit...
Value
90 (kg/s)
9.4.7. Turbo Model
1. Enable the Turbo Model.
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Domain → Turbo Model and select Enable.
2. Create the turbo interfaces.
Domain → Turbo Model → Turbo Create...
The Frozen Rotor method will be modeled using the No Pitch-Scale (NPS) interface which allows
for connecting a 360-degree interface to another 360-degree interface.
a. Enter nps for Mesh Interface.
b. Select interface-impeller-outlet from the Interface Zones Side 1 selection list.
c. Select interface-impeller-inlet from the Interface Zones Side 2 selection list.
d. Enable the General Turbo Interface option in the Interface Options group box.
e. Select No Pitch-Scale in the Pitch-Change Types group box under General Turbo Interface.
f.
Click Create/Edit and close the Create/Edit Turbo Interfaces dialog box.
3. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
Fluent will perform various checks on the mesh and will report the progress in the console. Make sure
that the reported minimum volume is a positive number.
Note that if this step is performed before creating the mesh interface, the check will fail because Fluent
will detect that the interface is missing.
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9.4.8. Solution
1. Specify the solution methods.
Solution → Solution → Methods...
a. Select Green-Gauss Node Based from the Gradient drop-down list in the Spatial Discretization group box.
b. Enable the High Order Term Relaxation option.
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c. Retain the default selections.
2. Create a surface report definition for total pressure at the outlet.
Solution → Reports → Definitions → New → Surface Report → Mass-Weighted Average...
a. Enter p-out for the Name of the surface report definition.
b. Select Pressure... and Total Pressure from the Field Variable drop-down lists.
c. Select Outlet from the Surfaces selection list.
This automatically selects all the outlet boundary conditions that have been specified.
d. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
3. Create a surface report definition for total pressure at the inlet.
Solution → Reports → Definitions → New → Surface Report → Mass-Weighted Average...
a. Enter p-in for the Name of the surface report definition.
b. Select Pressure... and Total Pressure from the Field Variable drop-down lists.
c. Select Inlet from the Surfaces selection list.
d. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
4. Create a surface report definition for blade pressure.
Solution → Reports → Definitions → New → Surface Report → Integral...
a. Enter p-blade for the Name of the surface report definition.
b. Select Pressure... and Static Pressure from the Field Variable drop-down lists.
c. Select blade from the Surfaces selection list.
d. Click OK to save the surface report definition settings and close the Surface Report
Definition dialog box.
5. Create an expression for pump head.
Solution → Reports → Definitions → New → Expression...
a. Enter the expression ({p-out} - {p-in}) / (998.2[kg/m^3] * 9.81[m/s^2]).
You can insert the report definitions you previously created using the Report Definitions dropdown list under Select Operand Field Functions from and clicking Select.
The expression uses 998.2 as the density of water [kg/m^3] and 9.81 as the acceleration of the
fluid due to gravity [m/s^2].
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b. Enter head for Name.
c. Select Report Plot
d. Select Print to Console
e. Click OK to save the expression and close the Expression Report Definition dialog box.
6. Initialize the solution.
Solution → Initialization
a. Click More Settings... to open the Hybrid Initialization dialog box.
b. Select Absolute under Reference Frame.
c. Click OK to close the Hybrid Initialization dialog box.
d. Click Initialize to initialize the solution.
7. Save the case file (pump_volute.cas.h5).
File → Write → Case...
8. Start the calculation.
Solution → Run Calculation → Run Calculation...
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a. Enter 10 for Timescale Factor.
b. Enter 200 for Number of Iterations.
c. Click Calculate.
You can monitor the progression of the residuals and the pump head during the run.
Figure 9.2: Convergence History of the Pump Head
9. Save the case and data files (pump_volute.cas.h5 and pump-volute.dat.h5).
File → Write → Case & Data...
9.4.9. Postprocessing
1. Determine the head generated from the pump
Solution → Reports → Definitions → Edit...
a. Select head and p-blade from the Report Definitions selection list.
b. Click Compute.
The head generated by the pump and pressure integral on the blade are printed to the console
and are approximately 20 [m] and 5560 [pascal m^2], respectively.
2. Create a contour showing the flow uniformity at the outlet.
Results → Graphics → Contours → New...
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a. Enter contour-vel-out for Contour Name.
b. Ensure that the Filled option is enabled in the Options group box.
c. Disable the Global Range option in the Options group box.
d. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
e. Deselect all surfaces and select Outlet from the Surfaces selection list.
f.
Select Draw Mesh.
g. On the Mesh Display dialog box that opens, deselect all surfaces and select the Wall surface
type from the Surfaces selection list.
h. Click Display and close the Mesh Display dialog box.
i.
Click Save/Display and close the Contours dialog box. Orient the view as shown in Figure 9.3: Contours of Velocity Magnitude at the Outlet (p. 394)
This gives an idea of how the fluid is exiting the volute.
Figure 9.3: Contours of Velocity Magnitude at the Outlet
3. Create a contour showing cross-sectional pressure.
Results → Graphics → Contours → New...
a. Enter contour-pressure-wall for Contour Name
b. Ensure that the Filled option is enabled in the Options group box.
c. Disable the Global Range option in the Options group box.
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d. Select Banded in the Coloring group box.
e. Ensure Pressure... and Static Pressure are selected from the Contours of drop-down lists.
f.
Select Wall from the Surfaces selection list.
g. Click Save/Display and close the Contours dialog box.
The increasing pressure in the flow domain can be seen in the contour plot.
Figure 9.4: Contours of Static Pressure on the Walls
4. Create filled contours of static pressure.
Results → Graphics → Contours → New...
a. Enter contour-pressure for Contour Name
b. Ensure that the Filled option is enabled in the Options group box.
c. Select Banded in the Coloring group box.
d. Ensure Pressure... and Static Pressure are selected from the Contours of drop-down lists.
e. Select blade, impeller-hub and inblock-hub from the Surfaces selection list.
f.
Click Save/Display and close the Contours dialog box.
Pressure distribution in the flow domain is plotted in graphics window.
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Figure 9.5: Contours of Static Pressure
5. Save the case file (pump_volute.cas.h5).
File → Write → Case...
9.5. Summary
In this tutorial you completed a fluid flow simulation to evaluate the performance of a pump and volute.
You created a custom expression to determine the head generated by the pump. While steady-state
simulation was used to model the pump performance using the frozen rotor method, this simulation
can be converted to a transient rotor stator simulation by following these steps:
• Switch the solver to transient
• In the impeller cell zone, change the motion from Frame Motion to Mesh Motion by clicking
on Copy to Mesh Motion
• In the Run Calculation panel, enter Time Step
You can watch a video of this case being set up, solved, and postprocessed at:
9.6. Further Improvements
This tutorial guides you through the steps to reach a basic solution. You can explore what effect varying
certain parameters, such as impeller speed and outlet flow, have on the performance of the pump.
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Chapter 10: Modeling Blade Row Interaction using
Steady-State and Transient Simulations
This tutorial is divided into the following sections:
10.1. Introduction
10.2. Prerequisites
10.3. Problem Description
10.4. Setup and Solution
10.5. Summary
10.1. Introduction
In this tutorial, you will setup a fluid flow simulation to evaluate the performance of a 1.5 stage compressor using a steady state mixing plane suimulaiton and then a transient pitch-scale simulation.
This tutorial demonstrates how to do the following:
• Set up a mixing plane and pitch scale turbo interface models to simulate flow in a compressor.
• Describe wall motion and other boundary conditions.
• Specify appropriate solver settings.
• Add and monitor expressions.
• Calculate expressions and display contours.
10.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
10.3. Problem Description
The problem to be considered is the modeling of a compressor with an inlet guide vane, rotor and
stator as shown in Figure 10.1: Case Geometry (p. 398). This geometry is the first three rows of the 4.5
stage axial Hannover compressor (Courtesy of TFD Hannover). The inlet guide vane has 26 vanes, the
rotor has 23 blades and rotates at a velocity of 17100 RPM and the stator has 30 passages. The total
presure at the inlet is 60,000 pa and a gauge total pressure of 60500 Pa at the outlet. A steady state
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Modeling Blade Row Interaction using Steady-State and Transient Simulations
mixing plane and a transient rotor/stator pitch-scale simulations will be performed to determine the
efficiency of the compressor.
Figure 10.1: Case Geometry
10.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
10.4.1. Preparation
10.4.2. Mesh
10.4.3. Solver Settings for the Steady State Mixing Plane Model
10.4.4. Models
10.4.5. Materials
10.4.6. Cell Zone Conditions for the Steady State Mixing Plane Model
10.4.7. Operating Conditions
10.4.8. Boundary Conditions for the Steady State Mixing Plane Model
10.4.9. Solution of the Steady State Mixing Plane Model
10.4.10. Postprocessing of the Steady State Mixing Plane Model
10.4.11. Solver Settings for the Transient Pitch Scale Model
10.4.12. Reference Values
10.4.13. Interface Conditions for the Transient Pitch Scale Model
10.4.14. Cell Zone Conditions for the Transient Pitch Scale Model
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Setup and Solution
10.4.15. Boundary Conditions for the Transient Pitch Scale Model
10.4.16. Solution settings for the Transient Pitch Scale Model
10.4.17. Postprocessing for the Transient Pitch Scale Model
10.4.1. Preparation
To prepare for running this tutorial:
1.
Download the hannover_compressor.zip file here.
2.
Unzip hannover_compressor.zip to your working directory.
The mesh file hannover_1.5Stage.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 4 under Parallel (Local Machine).
10.4.2. Mesh
1. Read the mesh file hannover_1.5Stage.msh.
File → Read → Mesh...
As Fluent reads the mesh file, it will report the progress in the console.
10.4.3. Solver Settings for the Steady State Mixing Plane Model
In the Solver group box of the Physics ribbon tab, retain the default selection of the steady pressurebased solver.
Physics → Solver
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10.4.4. Models
1. Set up your models for the CFD simulation using the Models group box of the Physics ribbon
tab.
2. Enable heat transfer by activating the energy equation.
Setup → Models → Energy On
3. Enable the -
SST turbulence model.
Physics → Models → Viscous...
a. Retain the default k-omega SST turbulence model.
b. Click OK.
Compared to other two-equation models, the - SST turbulence model effectively predicts flow separation in turbomachinery, allowing for accurate evaluation of pump performance.
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Setup and Solution
10.4.5. Materials
1. Set the properties for air, the default fluid material.
Setup → Materials → Fluid → air
Edit...
a. Select ideal-gas from the Density drop-down list.
b. Click Change/Create to save these settings.
c. Close the Create/Edit Materials dialog box.
10.4.6. Cell Zone Conditions for the Steady State Mixing Plane Model
All fluid zones must be reviewed to ensure that the Rotation-Axisis specified correctly, as well as,
the Rotational Velocity for rotating zones.
1. Set the cell zone conditions for the b-rotor1.
Setup → Cell Zone Conditions → Fluid → b-rotor1
Edit...
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a. Select Frame Motion.
b. Ensure that the correct Rotation-Axis is specified.
c. For Rotational Velocity > Speed (rpm), specify 17100.
d. Click Apply and close the Fluid dialog box .
2. Ensure that the correct Rotation-Axis is specified for the a-igv and c-stator1 zones.
10.4.7. Operating Conditions
1. Set the operating pressure.
Setup →
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The Operating Conditions dialog box can also be accessed from the Cell Zone Conditions task page.
a. Enter 0 Pa for Operating Pressure.
b. Click OK to close the Operating Conditions dialog box.
10.4.8. Boundary Conditions for the Steady State Mixing Plane Model
1. Set the boundary conditions for the inlet.
Setup → Boundary Conditions → Inlet → inlet → Edit...
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a.
i.
Enter a value of 60000 Pa for Gauge Total Pressure.
ii. Enter a value of 58000 Pa for Supersonic/Initial Gauge Pressure.
iii. Select Normal to Boundary for the Direction Specificaiton Method.
iv. Retain Intensity and Viscosity Ratio from the Specification Method drop-down list in
the Turbulence group box.
v. Retain the default value of 5% for Turbulent Intensity and 10 for Turbulent Viscosity
Ratio.
vi. Click the Thermal tab and enter 288.15 K for Temperature.
vii. Click Apply and close the Pressure Inlet dialog box.
2. Set the boundary conditions for the outlet.
Setup → Boundary Conditions → Outlet → outlet → Edit...
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a.
i.
Enter a value of 60500 Pa for Gauge Pressure.
ii. Select From Neighbouring Cell for the Backflow Direction Specificaiton Method.
iii. Enable Radial Equilibrium Pressure Distribution and Average Pressure Specification.
iv. Retain Intensity and Viscosity Ratio from the Specification Method drop-down list in
the Turbulence group box.
v. Retain the default value of 5% for Turbulent Intensity and 10 for Turbulent Viscosity
Ratio.
vi. Click the Thermal tab and enter 300 K for Temperature.
vii. Click Apply and close the Pressure Outlet dialog box.
3. By default, when the fluid zone is rotating, all the walls attached to the fluid zone will be rotating.
Since the rotor has a tip gap and the shroud is stationary in the absolute frame, we need to
modify the wall boundary condition for the rotor shroud. Set the wall boundary condition for rotor.
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Setup → Boundary Conditions → Wall → rotor1-shroud
Edit...
a.
i.
Select Moving Wall for the Wall Motion.
ii. Select Absolute and Rotational for the Motion.
iii. Ensure that the correct Rotation-Axis is specified.
iv. Click Apply and close the Wall dialog box.
4. Set the rotational periodic boundary conditions for the inlet guide vane, rotor and stator
Setup → Boundary Conditions → Symmetry → periodic_igv-per-side1_igv-per-side2 and
symmetry-15
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Periodic...
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a.
i.
Enter a value of periodic_igv for Zone Name.
ii. Select Conformal for the Type.
iii. Select Rotational for the Type.
iv. Ensure that the correct Rotation-Axis is specified.
v. Click Create.
Similarily, create the periodic condtions for the rotor and stator.
a. Create the periodic_rotor by selecting periodic_rotor1-per-sdie2_rotor1-per-side1 and symmetry-18.
b. Create the periodic_stator by selecting periodic_stator1-per-side-1_stator1-perside2 and symmetry-27.
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5. Create a mixing plane interfaces between the inlet guide vane and rotor and between the rotor
and stator.
a. Enable the Turbo Model and define the topology of the flow domain.
Domain → Turbo Model and select Enable.
b. Open the Create/Edit Turbo Interfaces dialog box.
Domain → Turbo Model → Turbo Create...
c. Create a mesh interface for the rotor tip gap.
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i.
Enter rotor1-tipgap-int for Interface Name .
ii. Select tip-r1-side1 and tip-r1-side2 from Boundary Zones list.
iii. Click Create/Edit.
d. Create a mesh interface between the inlet guide vane and the rotor.
i.
Enter mpm1 for the Mesh Interface name.
ii. Select igv-r1-upstream for Interface Zone Side 1 and igv-r1-downstream for
Interface Zone Side 2.
iii. Select General Turbo Interface from the Interface Options group box.
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Setup and Solution
iv. Select Mixing Plane for the Pitch-Change Types.
v. Click Create/Edit.
e. Create a mesh interface between the rotor and the stator.
i.
Enter mpm2 for the Mesh Interface name.
ii. Select r1-s1-upstream for Interface Zone Side 1 and r1-s1-downstream for Interface Zone Side 2.
iii. Select General Turbo Interface from the Interface Options group box.
iv. Select Mixing Plane for the Pitch-Change Types.
v. Click Create/Edit.
vi. Close the Create/Edit Turbo Interfaces dialog box.
6. Define the Turbo Topology
Domain → Turbo Model → Turbo Topology...
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a. Enter topo1 for the Turbo Topology Name name.
b. Select igv-hub, rotor1-hub and stator1-hub for the Surfaces.
c. Select Casing in the Boundaries group box and then select igv-shroud, rotor1-shroud
and stator1-shroud for the Surfaces.
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Setup and Solution
d. Select Theta Periodic in the Boundaries group box and then select periodic_igv, periodic_rotor and periodic_stator for the Surfaces.
e. Select Inlet in the Boundaries group box and then select inlet for the Surfaces.
f.
Select Outlet in the Boundaries group box and then select outlet for the Surfaces.
g. Select Blade in the Boundaries group box and then select igv-vane, rotor1-blade and
stator1-vane for the Surfaces.
h. Click Define and close the Turbo Topology dialog box.
10.4.9. Solution of the Steady State Mixing Plane Model
1. Specify the solution methods.
Solution → Solution → Methods...
Retain the default selection of Coupled from the Scheme drop-down list.
2. Create a surface report definition for quantities needed to calculate the compressor efficiency.
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Solution → Reports → Definitions → New → Surface Report → Area-Weighted Average
a. Enter ave_po_in for the Name of the surface report definition.
b. Select Pressure... and Total Pressure from the Field Variable drop-down lists.
c. Select Inlet from the Surfaces selection list.
d. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
Similary, create surface report definitions for:
a. Area-Weighted Average Total pressure at the outlet ave_po_out.
b. Area-Weighted Average Total Temperature at the inlet ave_to_in.
c. Area-Weighted Average Total Temperature at the outlet ave_to_out.
d. Mass Flow Rate at the stator outlet for one passagemfr_1psg_out
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Setup and Solution
3. Create expression report definition for pressure ratio.
Solution → Reports → Definitions → New → Expression...
a. Enter p-ratio for the Name of the surface report definition.
b. You can insert the report definitions you previously created using the Report Definitions dropdown list under Select Operand Field Functions from and clicking Select.
c. Enter the expression ({ave_po_out}/{ave_po_in}).
d. Select Report Plot
e. Click OK to save the surface report definition settings and close the Expression Report
Definition dialog box.
4. Create an expression report definition for total mass out flow.
Solution → Reports → Definitions → New → Expression...
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a. Enter mfr_out_360 for Name.
b. Enter the expression {mfr_1psg_out}*30.
c. Select Report Plot
d. Select Print to Console
e. Click OK to save the expression and close the Expression Report Definition dialog box.
5. Create an expression report definition for compressor efficiency.
Solution → Reports → Definitions → New → Expression...
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Setup and Solution
a. Enter iso_efficency for Name.
b. Enter the expression ( ({ave_to_in}* ( {p-ratio}**(0.4/1.4) - 1))/
({ave_to_out}-{ave_to_in}) ) * 100.00.
c. Select Report Plot
d. Select Print to Console
e. Click OK to save the expression and close the Expression Report Definition dialog box.
6. Specify the pump head percentage change to be the convergence condition to be used for solution
monitoring.
Solution → Reports → Residuals
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a. Select Advanced Options to open the panel.
b. Select Scale and Compute Local Scale in the Residual Values group box.
c. Select local scaling from the Reporting Option drop down list.
d. Select Absolute under Convergence Criterion.
e. Click OK to close the Residual Monitors dialog box.
7. Initialize the flow field using the Initialization group box of the Solution ribbon tab.
Solution → Initialization → More Settings...
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Setup and Solution
a. Select Absolute to open the Reference Frame group box.
b. Select Use Specified Initial Pressure on Inlets and click OK to close the Hybrid Initialization
dialogue box.
c. Click Initialize.
8. Save the case file (hannover_1.5Stage.cas.h5).
File → Write → Case...
9. Start the calculation.
Solution → Run Calculation → Run Calculation...
a. Enter 10 for Timescale Factor.
b. Enter 100 for Number of Iterations.
c. Click Calculate.
d. As the solution progresses, the plots of pressure ratio, outlet mass flow rate and the efficiency
all flatten out indicating the solution has converged.
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Figure 10.2: Pressure Ratio
Figure 10.3: Outlet Mass Flow Rate
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Setup and Solution
Figure 10.4: Efficiency
10.4.10. Postprocessing of the Steady State Mixing Plane Model
The flow shows the typical behavior when solving the blade row using the mixing-plane model, the
wake from the upstream rows and the potential flow from the downstream rows are mixed out across
the interface.
1. Create spanwise surfaces for the inlet guide vane, rotor and stator.
Results → Surface → Create → Iso-Surface...
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a. Create inlet guide vane spanwise surface
i.
Enter igv-span=0.5 for Name.
ii. Select Mesh... and Spanwise Coordinate from the drop-down lists.
iii. Click Compute.
iv. Enter 0.5 for Iso-Values.
v. a-igv from the Zones selection list.
vi. Click Create.
vii. In a similar manner, create spanwise surfaces for the rotor-span=0.5 and statorspan=0.5 and close the Iso-Surface dialog box.
2. Display velocity magnitude contours on the mid span.
Results → Graphics → Contours → New...
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Setup and Solution
Figure 10.5: Contours of Velocity Magnitiue
a. Enter contour-span=0.5-velmag for Contour Name.
b. Disable the Global Range option in the Options group box.
c. Enable the Contour Lines option in the Options group box.
d. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
e. Select igv-span=0.5, rotor-span=0.5 and stator-span=0.5 from the Surfaces selection list.
f.
Select Draw Mesh.
g. On the Mesh Display dialog box that opens, select igv-hub, igv-vane, rotor1-blade,
rotor1-hub, stator1-hub and stator1-vane from the Surfaces selection list.
h. Click Display and close the Mesh Display dialog box.
i.
Click Save/Display and close the Contours dialog box.
3. Display static pressure contours on the mid span.
Results → Graphics → Contours → New...
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Figure 10.6: Contours of Static Pressure
a. Enter contour-span=0.5-pressure for Contour Name
b. Disable the Global Range option in the Options group box.
c. Enable the Contour Lines option in the Options group box.
d. Ensure Pressure... and Static Pressure are selected from the Contours of drop-down lists.
e. Select igv-span=0.5, rotor-span=0.5 and stator-span=0.5 from the Surfaces selection list.
f.
Select Draw Mesh.
g. Click Display and close the Mesh Display dialog box.
h. Click Save/Display and close the Contours dialog box.
4. Display static temperature contours on the mid span.
Results → Graphics → Contours → New...
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Setup and Solution
Figure 10.7: Contours of Static Temperature
a. Enter contour-span=0.5-temperature for Contour Name
b. Disable the Global Range option in the Options group box.
c. Enable the Contour Lines option in the Options group box.
d. Ensure Temperature... and Static Temperature are selected from the Contours of drop-down
lists.
e. Select igv-span=0.5, rotor-span=0.5 and stator-span=0.5 from the Surfaces selection list.
f.
Select Draw Mesh.
g. Click Display and close the Mesh Display dialog box.
h. Click Save/Display and close the Contours dialog box.
5. Save the case and data files (hannover_1.5Stage.cas.h5 and hannover_1.5Stage.dat.h5).
File → Write → Case & Data...
10.4.11. Solver Settings for the Transient Pitch Scale Model
In the Solver group box of the Physics ribbon tab, select transient.
Physics → Solver
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10.4.12. Reference Values
Set the reference values as the inlet conditions. This will be needed to calculate entropy.
Setup → Reference Values
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Setup and Solution
10.4.13. Interface Conditions for the Transient Pitch Scale Model
1. Modify the a mixing plane interfaces between the inlet guide vane and rotor and between the
rotor and stator.
Setup → Mesh Interface → mpm1
Edit...
a. Create a mesh interface between the inlet guide vane and the rotor.
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i.
Enter ps1 for the Mesh Interface name.
ii. Select Pitch-Scale for the Pitch-Change Types.
iii. Click Create/Edit.
b. Create a mesh interface between the rotor and the stator.
i.
Select the mpm2 interface.
ii. Enter ps2 for the Mesh Interface name.
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Setup and Solution
iii. Select Pitch-Scale for the Pitch-Change Types.
iv. Click Create/Edit.
v. Close the Creat/edit Turbo Interfaces dialog box.
10.4.14. Cell Zone Conditions for the Transient Pitch Scale Model
The rotor zone needs to midified to use mesh motion.
1. Modify the cell zone conditions for the b-rotor1.
Setup → Cell Zone Conditions → Fluid → b-rotor1
Edit...
a. Click Copy to Mesh Mostion.
b. Click Apply and close the Fluid dialog box .
10.4.15. Boundary Conditions for the Transient Pitch Scale Model
The pressure-average option is not recommended for unsteady simulations and may result in nonphysical pressure feedback.
1. Modify the Outlet boudary condition.
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Setup → Boundary Conditions → Outlet → outlet → Edit...
a.
i.
Disable the Average Pressure Specification.
ii. Click Apply and close the Pressure Outlet dialog box.
10.4.16. Solution settings for the Transient Pitch Scale Model
1. Specify the solution methods.
Solution → Solution → Methods...
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Setup and Solution
a. Ensure Coupled from the Scheme drop-down list in the Pressure-Velocity Coupling group
box.
b. Select Second Order Implicit from the Transient Formulation drop-down list.
2. Modify the report plots to use an exponential axis for the flow time.
Solution → Monitors → Report Plots → iso_effiiciency-rplot
Edit...
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a. Click Axes... in the Plot Window group box.
b. Select X in the Axis group box.
c. Select Exponential and set the Precision to 2.
d. Click Apply and close the Axes - Report Plots dialog box.
e. Click OK to close the Edit Report Plot dialog box.
Similary, update the report plots for the mfr_out_360-rplot and p-ratio-rplot report plots.
3. Start the calculation.
Solution → Run Calculation → Run Calculation...
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Setup and Solution
a. Select Period-Based from the drop down list for Method in the Time Advancement group
box.
b. The rotor is running at 17100 rpm and has 23 pasages. Therefore the period of the rotor is
0.000152555 seconds. Enter 0.000152555 for Period (s) in the Parameters group box.
c. Enter 40 for Time Steps per Period.
d. Enter 5 for the Total Periods.
e. Enter 10 for Max Iterations/Time Steps.
f.
Click Calculate.
g. The plots of pressure ratio, outlet mass flow rate and the efficiency display the transient nature
of the solution. The fluctuation in the efficiency, mass flow rate and pressure-ratio is expected,
and is due to the blade passing interaction.
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Figure 10.8: Pressure Ratio
Figure 10.9: Outlet Mass Flow Rate
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Setup and Solution
Figure 10.10: Efficiency
4. Save the case and data files (hannover_1.5Stage_trs.cas.h5 and hannover_1.5Stage_trs.dat.h5).
File → Write → Case & Data...
10.4.17. Postprocessing for the Transient Pitch Scale Model
Unlike in the steady-state mixing plane solution in transient simulation, the wake will cross the interface,
but since the pitch-scale model approximation is used we see discontinuity in the wake contours.
This can be seen by plotting contours of entropy.
1. Display entropy contours on the mid span.
Results → Graphics → Contours → New...
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Modeling Blade Row Interaction using Steady-State and Transient Simulations
Figure 10.11: Contours of Entropy
a. Disable the Global Range, Auto Range and Clip to Rangeoption in the Options group box.
b. Select Temperature and Entropy from the Contours of drop down list
c. Select igv-span=0.5, rotor-span=0.5 and stator-span=0.5 from the Surfaces selection list.
d. Click Compute.
e. Enter -7 for the Min and 80 for the Max.
f.
g.
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Click Display.
View → Views..
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Setup and Solution
Select Define... in the Periodic Repeats group box.
i.
Select a-igv.
ii. Select igv-span=0.5from the Surfaces selection list.
iii. Enter 2 for the Number of Repeats.
iv. Click Set.
v. Select b-rotor1.
vi. Select rotor-span=0.5from the Surfaces selection list.
vii. Click Set.
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Modeling Blade Row Interaction using Steady-State and Transient Simulations
viii.Select c-stator1.
ix. Select stator-span=0.5from the Surfaces selection list.
x. Enter 2 for the Number of Repeats.
xi. Click Set.
xii. Close the Graphics Periodicity dialog box.
xiii. Close the Views dialog box.
2. Display velocity magnitude contours on the mid span.
Figure 10.12: Contours of Velocity Magnitiue
a. Enable the Auto Range in the Options group box.
b. Select Velocity and Velocity Magnitude from the Contours of drop down list
c. Click Display.
3. Display static pressure contours on the mid span.
Results → Graphics → Contours → contour-span=0.5-pressure
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Edit...
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Setup and Solution
Figure 10.13: Contours of Static Pressure
a. Select Pressure and Static Pressure from the Contours of drop down list
b. Click Display.
4. Display static temperature contours on the mid span.
Results → Graphics → Contours → contour-span=0.5-temperature
Edit...
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Modeling Blade Row Interaction using Steady-State and Transient Simulations
Figure 10.14: Contours of Static Temperature
a. Select Temperature and Static Temperature from the Contours of drop down list
b. Click Display and close the Contours dialog box.
10.5. Summary
In this tutorial you completed a fluid flow simulation to evaluate the performance of a compressor.
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Chapter 11: Using Sliding Meshes
This tutorial is divided into the following sections:
11.1. Introduction
11.2. Prerequisites
11.3. Problem Description
11.4. Setup and Solution
11.5. Summary
11.1. Introduction
The analysis of turbomachinery often involves the examination of the transient effects due to flow interaction between the stationary components and the rotating blades. In this tutorial, the sliding mesh
capability of ANSYS Fluent is used to analyze the transient flow in an axial compressor stage. The rotorstator interaction is modeled by allowing the mesh associated with the rotor blade row to rotate relative
to the stationary mesh associated with the stator blade row.
For turbomachinery applications, it is recommended that connecting rotating and stationary zones
utilizes General Turbo Interfaces (GTI) which can handle any pitch-change model. To know more about
GTI interfaces see tutorial Modeling Blade Row Interaction using Steady-State and Transient Simulations
in the Fluent Tutorials (p. 397). This tutorial will show an alternative way of connecting rotating and stationary zones (using periodic repeat interface). While this tutorial is using a turbomachinery application
the outlined procedure can be used for other flow applications that require the connection of similarpitch rotating and stationary zones.
This tutorial demonstrates how to do the following:
• Create periodic zones.
• Set up the transient solver and cell zone and boundary conditions for a sliding mesh simulation.
• Set up the mesh interfaces for a periodic sliding mesh model.
• Sample the time-dependent data and view the mean value.
11.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
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11.3. Problem Description
The model represents a single-stage axial compressor composed of two blade rows. The first row is the
rotor with 16 blades, which is operating at a rotational speed of 37,500 rpm. The second row is the
stator with 32 blades. The blade counts are such that the domain is rotationally periodic, with a periodic
angle of 22.5 degrees. This enables you to model only a portion of the geometry, namely, one rotor
blade and two stator blades. Due to the high Reynolds number of the flow and the relative coarseness
of the mesh (both blade rows are composed of only 13,856 cells total), the analysis will employ the inviscid model, so that ANSYS Fluent is solving the Euler equations.
Figure 11.1: Rotor-Stator Problem Description
11.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
11.4.1. Preparation
11.4.2. Mesh
11.4.3. General Settings
11.4.4. Models
11.4.5. Materials
11.4.6. Cell Zone Conditions
11.4.7. Boundary Conditions
11.4.8. Operating Conditions
11.4.9. Mesh Interfaces
11.4.10. Solution
11.4.11. Postprocessing
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Setup and Solution
11.4.1. Preparation
To prepare for running this tutorial:
1.
Download the sliding_mesh.zip file here.
2.
Unzip sliding_mesh.zip to your working directory.
The mesh file axial_comp.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
11.4.2. Mesh
1. Read in the mesh file axial_comp.msh.
File → Read → Mesh...
11.4.3. General Settings
1. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and will report the progress in the console. Ensure
that the reported minimum volume is a positive number.
Warnings will be displayed regarding unassigned interface zones, resulting in the failure of the mesh
check. You do not need to take any action at this point, as this issue will be rectified when you define
the mesh interfaces in a later step.
2. Examine the mesh (Figure 11.2: Rotor-Stator Display (p. 444)).
Orient the view to display the mesh as shown in Figure 11.2: Rotor-Stator Display (p. 444). The inlet of
the rotor mesh is colored blue, the interface between the rotor and stator meshes is colored yellow,
and the outlet of the stator mesh is colored red.
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Figure 11.2: Rotor-Stator Display
3. Define the units for the model.
Setup →
General → Units...
a. Select angular-velocity from the Quantities selection list.
b. Select rpm from the Units selection list.
c. Select pressure from the Quantities selection list.
Scroll down the Quantities list to find pressure.
d. Select atm from the Units selection list.
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Setup and Solution
e. Close the Set Units dialog box.
4. Change zones rotor-per-1 and rotor-per-3 from wall zones to periodic zones.
Setup → Boundary Conditions → Wall
a. Click rotor-per-1 to select the tree item.
b. While holding down the Ctrl key, click rotor-per-3 to add the tree item to the selection.
Note:
The first zone that is selected will be used as the periodic zone, while the second
zone will be used as the shadow zone. Although it is not significant in this case,
the order in which the two zone pairs are selected may affect simulation results.
c. Right-click the selected tree items and select Periodic... to open the Create Periodic dialog
box.
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d. Select Rotational in the Type group box.
e. Click Create to close the Create Periodic dialog box.
5. Similarly, change the following wall zone pairs to periodic zones:
Zone Pairs
Respective Zone IDs
rotor-per-2 and rotor-per-4
12 and 11
stator-per-1 and stator-per-3
26 and 27
stator-per-2 and stator-per-4
24 and 25
11.4.4. Models
1. Enable the inviscid model.
Setup → Models → Viscous
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Edit...
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Setup and Solution
a. Select Inviscid in the Model list.
b. Click OK to close the Viscous Model dialog box.
11.4.5. Materials
1. Specify air (the default material) as the fluid material, using the ideal gas law to compute density.
Setup → Materials → Fluid → air
Edit...
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a. Retain the default entry of air in the Name text entry field.
b. Select ideal-gas from the Density drop-down list in the Properties group box.
c. Retain the default values for all other properties.
d. Click Change/Create and close the Create/Edit Materials dialog box.
As reported in the console, ANSYS Fluent will automatically enable the energy equation, since this is
required when using the ideal gas law to compute the density of the fluid.
2. Specify that it is a transient problem, to allow mesh motion.
Setup →
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General
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Setup and Solution
a. Retain the default selection of Pressure-Based in the Type list.
b. Select Transient in the Time list.
11.4.6. Cell Zone Conditions
Setup →
Cell Zone Conditions
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1. Set the cell zone conditions for the fluid in the rotor (fluid-rotor).
Setup →
450
Cell Zone Conditions →
fluid-rotor → Edit...
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Setup and Solution
a. Enable Mesh Motion.
b. Click the Mesh Motion tab.
c. Retain the default values of (0, 0, 1) for X, Y, and Z in the Rotation-Axis Direction group box.
d. Enter 37500 rpm for Speed in the Rotational Velocity group box.
e. Click Apply and close the Fluid dialog box.
2. Set the cell zone conditions for the fluid in the stator (fluid-stator).
Setup →
Cell Zone Conditions →
fluid-stator → Edit...
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a. Retain the default values of (0, 0, 1) for X, Y, and Z in the Rotation-Axis Direction group box.
b. Click Apply and close the Fluid dialog box.
11.4.7. Boundary Conditions
Setup →
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Boundary Conditions
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Setup and Solution
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1. Enter rotor-inlet into the Zone field to filter the zone list.
Setup →
Boundary Conditions →
rotor-inlet → Edit...
a. Enter 1.0 atm for Gauge Total Pressure.
b. Enter 0.9 atm for Supersonic/Initial Gauge Pressure.
For information about the Supersonic/Initial Gauge Pressure, see the Fluent User's Guide.
c. Click the Thermal tab and enter 288 K for Total Temperature.
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Setup and Solution
d. Click Apply and close the Pressure Inlet dialog box.
2. Enter stator-outlet into the Zone field to filter the zone list.
Setup →
Boundary Conditions →
stator-outlet → Edit...
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a. Enter 1.08 atm for Gauge Pressure.
b. Enable Radial Equilibrium Pressure Distribution.
c. Click the Thermal tab and enter 288 K for Backflow Total Temperature.
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Setup and Solution
d. Click Apply and close the Pressure Outlet dialog box.
Note:
The momentum settings and temperature you input at the pressure outlet will be used
only if flow enters the domain through this boundary. It is important to set reasonable
values for these downstream scalar values, in case flow reversal occurs at some point
during the calculation.
3. Retain the default boundary conditions for all wall zones.
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Setup →
Boundary Conditions →
rotor-blade-1 → Edit...
Note:
For wall zones, ANSYS Fluent always imposes zero velocity for the normal velocity
component, which is required whether or not the fluid zone is moving. This condition
is all that is required for an inviscid flow, as the tangential velocity is computed as part
of the solution.
11.4.8. Operating Conditions
1. Set the operating pressure.
Setup →
Boundary Conditions → Operating Conditions...
a. Enter 0 atm for Operating Pressure.
b. Click OK to close the Operating Conditions dialog box.
Since you have specified the boundary condition inputs for pressure in terms of absolute pressures,
you have to set the operating pressure to zero. Boundary condition inputs for pressure should always
be relative to the value used for operating pressure.
11.4.9. Mesh Interfaces
1. Disable the one-to-one interface creation method using the following text command, so that you
can create a mesh interface that uses the Periodic Repeats option.
>define/mesh-interfaces/one-to-one-pairing? no
2. Create a periodic mesh interface between the rotor and stator mesh regions.
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Setup and Solution
a. Open the Mesh Interfaces dialog box.
Setup → Mesh Interfaces
New...
b. Click Manual Create... to open the Create/Edit Mesh Interfaces dialog box.
c. Enter int for Mesh Interface.
d. Enable Periodic Repeats in the Interface Options group box.
Enabling this option, allows ANSYS Fluent to treat the interface between the sliding and non-sliding
zones as periodic where the two zones do not overlap.
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e. Select rotor-interface from the Interface Zones Side 1 selection list.
Note:
In general, when one interface zone is smaller than the other, it is recommended
that you choose the smaller zone as Interface Zone 1. In this case, since both zones
are approximately the same size, the order is not significant.
f.
Select stator-interface from the Interface Zones Side 2 selection list.
g. Click Create/Edit... and close the Create/Edit Mesh Interfaces dialog box.
h. Close the Mesh Interfaces dialog box.
3. Check the mesh again to verify that the warnings displayed earlier have been resolved.
Domain → Mesh → Perform Mesh Check
11.4.10. Solution
1. Set the solution parameters.
Solution → Solution → Methods...
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Setup and Solution
Select Coupled from the Pressure-Velocity Coupling group box.
2. Change the Solution Controls
Solution → Controls → Controls...
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a. Enter 0.5 for Momentum and Pressure in the Explicit Relaxation Factors group box.
b. Enter 0.9 for Temperature in the Under-Relaxation Factors group box.
3. Enable the plotting of residuals during the calculation.
Solution → Reports → Residuals...
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Setup and Solution
a. Ensure that the Plot is selected in the Options group box.
b. Enable Show Advanced Options and select relative from the Convergence Criterion dropdown list.
c. Enter 0.01 for Relative Criteria for each Residual (continuity, x-velocity, y-velocity, z-velocity, and energy).
d. Click OK to close the Residual Monitors dialog box.
4. Enable the plotting of mass flow rate at the inlet (rotor-inlet).
Solution → Reports → Definitions → New → Surface Report → Mass Flow Rate...
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Using Sliding Meshes
a. Enter surf-mon-1 for the Name of the surface report definition.
b. In the Create group box, enable Report File, Report Plot and Print to Console.
c. Enter rotor-inlet in the Surfaces field to filter the list.
d. Select rotor-inlet from the Surfaces selection list.
e. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
surf-mon-1-rplot and surf-mon-1-rfile that are automatically generated by Fluent appear in
the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report Files, respectively).
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Setup and Solution
5. Enable the plotting of mass flow rate at the outlet (stator-outlet).
Solution → Reports → Definitions → New → Surface Report → Mass Flow Rate...
a. Enter surf-mon-2 for the Name of the surface report definition.
b. In the Create group box, enable Report File, Report Plot and Print to Console.
c. Enter stator-outlet in the Surfaces field to filter the list.
d. Select stator-outlet from the Surfaces selection list.
e. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
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surf-mon-2-rplot and surf-mon-2-rfile that are automatically generated by Fluent appear in
the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report Files, respectively).
6. Enable the plotting of the area-weighted average of the static pressure at the interface (statorinterface).
Solution → Reports → Definitions → New → Surface Report → Area-Weighted Average...
a. Enter surf-mon-3 for the Name of the surface report definition.
b. In the Create group box, enable Report File, Report Plot and Print to Console.
c. Retain the default selection of Pressure... and Static Pressure from the Field Variable dropdown lists.
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Setup and Solution
d. Enter stator-interface in the Surfaces field to filter the list.
e. Select stator-interface from the Surfaces selection list.
f.
Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
surf-mon-3-rplot and surf-mon-3-rfile that are automatically generated by Fluent appear in
the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report Files, respectively).
7. Initialize the solution using the values at the inlet (rotor-inlet).
Solution → Initialization → Options...
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a. Select rotor-inlet from the Compute from drop-down list.
b. Select Absolute in the Reference Frame list.
c. Click Initialize.
8. Save the initial case file (axial_comp.cas.h5).
File → Write → Case...
9. Run the calculation for one revolution of the rotor.
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Setup and Solution
Solution → Run Calculation → Run Calculation...
a. Enter 6.6667e-6 s for Time Step Size.
The time step is set such that the passing of a single rotor blade is divided into 15 time steps. There
are 16 blades on the rotor. Therefore, in each time step the rotor rotates 360/16/15=1.5 degrees.
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With a rotational speed of 37,500 rpm (225,000 deg/sec), 1.5 degrees of rotation takes 1.5 / 2.25e5
= 6.6667e-6 sec.
b. Enter 240 for Number of Time Steps.
There are 16 blades on the rotor, and each rotor blade period corresponds to 15 time steps (see
above). Therefore, a complete revolution of the rotor will take 16*15=240 time steps.
c. Retain the default setting of 20 for Max Iterations/Time Step.
d. Click Calculate.
The residuals jump at the beginning of each time step and then fall at least two to three orders of
magnitude. Also, the relative convergence criteria is achieved before reaching the maximum iteration
limit (20) for each time step, indicating the limit does not need to be increased.
Figure 11.3: Residual History for the First Revolution of the Rotor
10. Examine the flow variable histories for the first revolution of the rotor (Figure 11.4: Mass Flow Rate
at the Inlet During the First Revolution (p. 471), Figure 11.5: Mass Flow Rate at the Outlet During
the First Revolution (p. 471), and Figure 11.6: Static Pressure at the Interface During the First Revolution (p. 472)).
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Setup and Solution
Figure 11.4: Mass Flow Rate at the Inlet During the First Revolution
Figure 11.5: Mass Flow Rate at the Outlet During the First Revolution
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Figure 11.6: Static Pressure at the Interface During the First Revolution
The flow variable histories show that the large variations in flow rate and interface pressure that occur
early in the calculation are greatly reduced as time-periodicity is approached.
11. Save the case and data files (axial_comp-0240.cas.h5 and axial_comp-0240.dat.h5).
File → Write → Case & Data...
Note:
It is a good practice to save the case file whenever you are saving the data file
especially for sliding mesh model. This is because the case file contains the mesh
information, which is changing with time.
Note:
For transient-state calculations, you can add the character string %t to the file name
so that the iteration number is automatically appended to the name (for example, by
entering axial_comp-%t for the File Name in the Select File dialog box, ANSYS
Fluent will save files with the names axial_comp-0240.cas.h5 and axial_comp0240.dat.h5).
12. Rename the report output file in preparation for further iterations.
Solution → Monitors → Report Files → surf-mon-1-rfile
472
Edit...
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Setup and Solution
a. Enter surf-mon-1b.out for Output File Base Name.
b. Click OK to close the Edit Report File dialog box.
13. Similarly, change the output file names for the surf-mon-2-rfile and surf-mon-3-rfile report file
definitions to surf-mon-2b.out and surf-mon-3b.out, respectively.
14. Continue the calculation for 720 more time steps to simulate three more revolutions of the rotor.
Solution → Run Calculation → Run Calculation...
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15. Examine the flow variable histories for the next three revolutions of the rotor to verify that the
solution is time-periodic (Figure 11.7: Mass Flow Rate at the Inlet During the Next 3 Revolutions (p. 475) Figure 11.8: Mass Flow Rate at the Outlet During the Next 3 Revolutions (p. 475), and
Figure 11.9: Static Pressure at the Interface During the Next 3 Revolutions (p. 476)).
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Setup and Solution
Figure 11.7: Mass Flow Rate at the Inlet During the Next 3 Revolutions
Figure 11.8: Mass Flow Rate at the Outlet During the Next 3 Revolutions
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Figure 11.9: Static Pressure at the Interface During the Next 3 Revolutions
16. Save the case and data files (axial_comp-960.cas.h5 and axial_comp-960.dat.h5).
File → Write → Case & Data...
17. Change the file names for surf-mon-1b.out, surf-mon-2b.out, and surf-mon-3b.out to surfmon-1c.out, surf-mon-2c.out, and surf-mon-3c.out, respectively (as described in a
previous step), in preparation for further iterations.
18. Add a point at the interface of the stator.
Results → Surface → Create → Point...
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Setup and Solution
a. Enter -0.02 for x0, -0.08 for y0, and -0.036 for z0 in the Point Surface dialog box.
b. Retain the default, point-1 for New Surface Name.
c. Click Create and close the Point Surface dialog box.
19. Enable plotting of the static pressure at a point on the stator interface (point-1).
Solution → Reports → Definitions → New → Surface Report → Vertex Average...
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a. Enter surf-mon-4 for the Name of the surface report definition.
b. In the Create group box, enable Report File, Report Plot and Print to Console.
c. Retain the defaults of Pressure and Static Pressure for Field Variable.
d. Enter point-1 in the Surfaces field to filter the list.
e. Select point-1 from the Surfaces selection list.
f.
Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
20. Continue the calculation for one final revolution of the rotor, while saving data samples for the
postprocessing of the time statistics.
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Setup and Solution
Solution → Run Calculation → Run Calculation...
a. Enter 240 for Number of Time Steps.
b. Enable Data Sampling for Time Statistics in the Options group box.
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Enabling Data Sampling for Time Statistics causes ANSYS Fluent to calculate and store mean
and root-mean-square (RMS) values of various quantities and field functions over the calculation
interval.
c. Click Calculate.
21. Save the case and data files (axial_comp-1200.cas.h5 and axial_comp-1200.dat.h5).
File → Write → Case & Data...
Figure 11.10: Static Pressure at a Point on The Stator Interface During the Final Revolution
11.4.11. Postprocessing
1. Examine the vertex-averaged static pressure at the stator during the final revolution of the rotor
(as calculated from surf-mon-4.out), and plot the data.
Results → Plots → FFT...
a. Click the Load Input File... button to open the Select File dialog box.
i.
Select All Files from the Files of type: drop-down list.
ii. Select surf-mon-4-rfile.out from the list of files.
iii. Click OK to close the Select File dialog box.
b. Click the Plot/Modify Input Signal... button to open the Plot/Modify Input Signal dialog
box.
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Setup and Solution
i.
Enable Subtract Mean Value in the Options group box.
ii. Enter flow-time as the X Axis Label.
iii. Select flow-time in the X Axis Variable drop-down list.
iv. Click Apply/Plot.
v. Close the Plot/Modify Input Signal dialog box.
c. Click Plot FFT in the Fourier Transform dialog box.
d. Click Axes... to open the Axes - Fourier Transform dialog box.
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e. Select exponential from the Type drop-down list, and set Precision to 1 in the Number
Format group box.
f.
Click Apply and close the Axes - Fourier Transform dialog box.
g. Click Plot FFT and close the Fourier Transform dialog box.
Figure 11.11: FFT of Static Pressure at the Stator
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Setup and Solution
The FFT plot clearly shows that the pressure fluctuations due to interaction at the interface are
dominated by the rotor and stator blade passing frequencies (which are 10 kHz and 20 kHz, respectively) and their higher harmonics.
2. Display contours of the mean static pressure on the walls of the axial compressor.
Results → Graphics → Contours → New...
a. Enter contour-mean-static-pressure for Contour Name.
b. Ensure Filled is enabled in the Options group box.
c. Select Banded in the Coloring group box.
d. Select Unsteady Statistics... and Mean Static Pressure from the Contours of drop-down
lists.
e. Select Wall from the Surface Types selection list.
Scroll down the Surfaces selection list to find Wall.
f.
Click Save/Display and close the Contours dialog box.
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g. Disable the Lighting option in the View ribbon tab.
h. Rotate the view to get the display as shown in Figure 11.12: Mean Static Pressure on the Outer
Shroud of the Axial Compressor (p. 484).
Shock waves are clearly visible in the flow near the outlets of the rotor and stator, as seen in the areas
of rapid pressure change on the outer shroud of the axial compressor.
Figure 11.12: Mean Static Pressure on the Outer Shroud of the Axial Compressor
3. Save the case file (axial_comp-1200.cas.h5).
File → Write → Case...
11.5. Summary
This tutorial has demonstrated the use of the sliding mesh model for analyzing transient rotor-stator
interaction in an axial compressor stage. The model utilized the coupled pressure-based solver in conjunction with the transient algorithm to compute the inviscid flow through the compressor stage. The
solution was calculated over time until the reported variables displayed time-periodicity (which required
several revolutions of the rotor), after which time-averaged data was collected while running the case
for the equivalent of one additional rotor revolution (240 time steps).
The Fast Fourier Transform (FFT) utility in ANSYS Fluent was employed to determine the time averages
from stored flow variable report data. You also used the FFT utility to examine the frequency content
of the transient report data. The observed peak corresponds to the passing frequency and the higher
harmonics of the passing frequency, which occurred at approximately 10,000 Hz.
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Chapter 12: Using Overset and Dynamic Meshes
This tutorial is divided into the following sections:
12.1. Prerequisites
12.2. Problem Description
12.3. Preparation
12.4. Mesh
12.5. Overset Interface Creation
12.6. Steady-State Case Setup
12.7. Unsteady Setup
12.8. Summary
The purpose of this tutorial is to provide guidelines and recommendations for setting up and solving
a dynamic overset mesh case. Overset mesh allows you to build up your case using multiple overlapping
meshes that automatically get connected by interpolating cell data in the overlapping regions. The
overset meshing technique is used in conjunction with the Six Degree of Freedom (6DOF) solver, allowing
bodies to move as a result of fluid and/or external forces.
In this tutorial, you will learn:
• Reading and appending mesh files into the Fluent solver and establishing a flow domain with
the overset approach from overlapping meshes.
• Best practices for overset mesh settings when two walls are close to each other or there is a very
tight gap.
• Compiling the UDF to specify the properties of the pod.
• Setting up the moving zones and hooking the UDF.
• Running a steady-state calculation and continuing an unsteady calculation for the problem.
• Best practices for monitoring and diagnosing an overset case and postprocessing the results.
Note:
Overset meshing has many applications beyond store separation. Refer to Overset Meshes
in the Fluent User's Guide for additional information on overset meshing capabilities.
12.1. Prerequisites
This tutorial is focused on overset meshing and it assumes that you are familiar with the ANSYS Fluent
interface and that you have a good understanding of the basic setup and solution procedures. Some
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of the basic steps in the setup and solution procedure will not be shown explicitly. In this tutorial, you
will use the dynamic mesh model and the Six Degree of Freedom model. If you have not used these
models before, refer to the Section on Dynamic Meshes in the ANSYS Fluent User’s Guide. You will use
a UDF to specify the properties of the pod. If you have not used UDFs before, refer to the Fluent Customization Manual.
12.2. Problem Description
A rescue pod is dropped from a moving airplane flying at Mach 0.8. As the pod falls, it is subjected to
pressure, viscous drag, and gravitational forces. These forces also create a moment on the pod, causing
it to rotate about its center of gravity.
The pod is released from the aircraft at t=0.
Figure 12.1: Schematic of Problem
The representation of the problem is shown in Figure 12.1: Schematic of Problem (p. 486) A close view
of the bay area and different walls with their interior zones are shown in Figure 12.2: Close View of Bay
Area (p. 487).
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Mesh
Figure 12.2: Close View of Bay Area
12.3. Preparation
1.
Download the overset_dynamic_mesh.zip file here.
2.
Unzip overset_dynamic_mesh.zip to your working directory.
The files Overset-background-mesh.msh, Overset-component-mesh.msh, and property.c can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 4 under Parallel (Local Machine).
12.4. Mesh
1.
Read the mesh file Overset-background-mesh.msh.
File → Read → Mesh...
As ANSYS Fluent reads the mesh file, it will report the progress in the console. This mesh has three different zones that allow for a greater level of refinement where the pod will be falling and less refinement
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Using Overset and Dynamic Meshes
at the far field. Dividing the background mesh into multiple zones allows for non-conformal interfaces
between the other zones that will not be in the overset interface.
Note:
Fluent uses the terminology of a component mesh and a background mesh. The mesh
containing the moving object is called component mesh and stationary mesh is called
the background mesh. The outer boundary of component mesh is referred as component
boundary.
2.
In this step you will create mesh interfaces between multiple zones in the stationary mesh. This
mesh has three cell zones- upstream, downstream, and fluid-background.
Domain → Interfaces → Mesh...
488
a.
Select interface-background-downstream and interface-downstream-background in the
Boundary Zones list.
b.
Enter downstream-background for Interface Name Prefix.
c.
Click Create.
d.
Select interface-background-upstream and interface-upstream-background in the
Boundary Zones list.
e.
Enter upstream-background for Interface Name Prefix.
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Mesh
f.
3.
Click Create and close the Mesh Interfaces dialog box.
Append the component mesh file
Domain → Zones → Append → Append Case File...
a.
Select overset-component-mesh.msh and click OK.
b.
Click OK in the Warning dialog box that appears stating that some zone IDs have changed.
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c.
If you have the Display Mesh After Reading option enabled in the Fluent Launcher, then
you must refresh the graphics window by right-clicking in the graphics window and selecting
Refresh Display.
Note:
Fluent will append the component mesh and two meshes will overlap each other.
If background and component meshes are present in the same mesh file, then you
can start directly from the mesh file without appending.
4.
Display the mesh.
Domain → Mesh → Display
a.
Select all surfaces and click Display.
b.
Close the Mesh Display dialog box.
Note:
There are approximately 110 K mesh elements in this case.
5.
Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
The mesh check fails with a warning. The warning states that there is an overset zone that is not a part
of any overset interface. If any zone already has overset type, we need to define overset-interface with
490
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Overset Interface Creation
available overset zone. If mesh does not have any overset type predefined, then this warning will not
come.
Note:
Fluent performs various checks on the mesh and reports the progress in the console
window. Pay attention to the reported minimum volume and make sure this is a positive
number.
12.5. Overset Interface Creation
1.
In this step you will ensure that the component boundary is properly defined as the overset
boundary type.
Setup → Boundary Conditions → Overset → overset_boundary
Type → overset
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Note:
ANSYS Meshing automatically assigns boundary types according to boundary names.
Meshes created in other meshing tools may require you to manually define all of the
boundary types.
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Overset Interface Creation
2.
Define Overset Interface.
Domain → Interfaces → Overset...
This opens the Create/Edit Overset Interfaces dialog box.
3.
a.
Enter overset-interface for Name.
b.
Select fluid-background from the Background group box and component from the Component group box.
c.
Click Create to create the overset interface.
d.
Close the Create/Edit Overset Interfaces dialog box.
Repeat the mesh check to confirm that it is successful.
Domain → Mesh → Check → Perform Mesh Check
4.
Define overset settings for creating an efficient interface.
Set the donor-priority-method to boundary-distance-based. This option is only available
through the TUI command:
/define/overset-interfaces/options/donor-priority-method 1
While establishing overset interface, Fluent does an optimization to get best location of the interface
while reducing the number of cells in the overlapping region that will participate in the calculation.
There are options to define the priority of the cell zones that will take part in the overset interface creation.
Zones defined as higher priority will be given more weightage. When cell zones have the same priority,
there are two methods that govern overlap minimization (see Overlap Minimization in the Fluent User's
Guide ): one method is cell volume based (proportional to the inverse of the cell volume) and other
method is boundary distance based (proportional to the inverse of the distance to the closest boundary).
Cell volume based works best if the component mesh resolution is fine near walls and increases
gradually away from walls and becomes similar in size to or larger than the background mesh.
Boundary distance based method works best where overlapping meshes have uniform and nearly
identical resolutions and therefore it is most suitable when two walls have small distance in between
them. In this example, the store wall is very near to the bay wall and the boundary distance based
method allows Fluent to create an overset interface somewhere middle of the gap. It is important to
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have sufficient cells overlapping each other between the gap region of two walls (at least 4 cells from
both walls), so it is better to create inflation layers on walls to resolve this requirement.
5.
In this step you will create the overset intersection, also referred to as hole cutting. When the case
is initialized, ANSYS Fluent automatically creates the overset intersection. Experts have the option
to investigate how the intersection is created by enabling expert options in the TUI:
/define/overset-interfaces/options/expert? yes
With expert options enabled, you can create the intersection using the following command:
/define/overset-interfaces/intersect-all
When prompted to keep bounding cells, press the Enter key to accept the default option of no.
Keep bounding cells? [no]
You can increase the overset verbosity to have Fluent print more information to the console for
any overset process. Verbosity settings range from 0 to 3 depending on the information required.
To increase verbosity, enter:
/define/overset-interfaces/options/verbosity 2
To list all overset interface related information, enter:
/define/overset-interfaces/list
12.6. Steady-State Case Setup
In this section you will set up the case for steady-state flow.
12.6.1. General Settings
Retain the setting of steady-state pressure-based solver.
Physics → Solver
12.6.2. Models
1.
Enable the energy equation.
Physics → Models → Energy
2.
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Specify the k-omega viscous model.
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Steady-State Case Setup
Physics → Models → Viscous...
a.
Retain the default selection of the k-omega SST viscous model.
b.
Enable the Viscous Heating and Production Limiter options.
c.
Click OK to close and confirm the model settings.
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12.6.3. Materials
Specify the properties for air.
•
Open the Create/Edit Materials dialog box.
Physics → Materials → Create/Edit
a.
Select ideal-gas from the Density drop-down list.
b.
Click Change/Create and close the dialog box.
12.6.4. Operating Conditions
Set the operating conditions.
Physics → Operating Conditions...
1.
Enter 0 Pa for Operating Pressure.
2.
Click OK to confirm the operating conditions.
12.6.5. Boundary Conditions
1.
Set the boundary conditions for the inlet.
Setup → Boundary Conditions → Inlet → pressure-inlet
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Steady-State Case Setup
2.
a.
Enter 154419.3 pa for Gauge Total Pressure.
b.
Enter 101325 pa for Supersonic/Initial Gauge Pressure.
c.
Retain Intensity and Viscosity Ratio as the Specification Method in the Turbulence group
box.
d.
Retain the default values of 5% and 10 for Turbulent Intensity and Turbulent Viscosity
Ratio respectively.
e.
Click Apply and close the Pressure inlet dialog box.
Set the boundary conditions for outlet.
Setup → Boundary Conditions → Outlet → pressure-outlet
Edit...
a.
Enter 101325 pa for Gauge Pressure.
b.
Retain Intensity and Viscosity Ratio as the Specification Method in the Turbulence group
box.
c.
Retain the default values of 5% and 10 for Backflow Turbulent Intensity and Backflow
Turbulent Viscosity Ratio respectively.
d.
Click Apply and close the Pressure Outlet dialog box.
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3.
Keep the defaults for all of the other boundary conditions.
12.6.6. Reference Values
Physics → Solver → Reference Values...
1.
Select pressure-inlet from the Compute from drop-down list.
2.
Select fluid-background from the Reference Zone drop-down list.
3.
Retain the default Reference Values as shown above.
12.6.7. Solution
In this section you will specify solution methods and controls that are appropriate for this overset
meshing case.
1.
Set the solution methods.
Solution → Solution → Methods...
498
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Steady-State Case Setup
1. In the Solution Methods task page, retain the default selections for the Spatial Discretization.
2.
Set the solution controls.
Solution → Controls → Controls...
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3.
a.
Review and retain the default settings.
b.
Click Limits... to open the Solution Limits dialog box.
c.
Enter 1e+07 for Maximum Turb. Viscosity Ratio.
d.
Click OK to accept the settings.
Define a report for the drag coefficient of the pod.
Solution → Reports → Definitions → New → Force Report → Drag...
500
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Steady-State Case Setup
a.
Enable Report File and Report Plot in the Create group box.
b.
Select wall-pod from the Wall Zones list.
c.
Click OK to create the report.
For additional information on writing report files, refer to "Creating Report Files" in the Fluent User's
Guide.
4.
Specify the residual monitor criterion for the solution equations.
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Solution → Reports → Residuals...
Enter 1e-06 as the Absolute Criterion for all of the Equations and then close the Residual
Monitors dialog box.
5.
Ensure Hybrid is selected as the initialization method in the Solution ribbon tab.
Click Initialize.
6.
Define parameters for calculation to a steady-state solution.
Solution → Run Calculation
a.
Enter 1000 for No. of Iterations.
Note:
If you are running in serial, then you must reorder the mesh prior to beginning
the calculation, using the mesh/reorder/reorder-domain text command.
This reordering is done automatically for parallel processes > 1.
b.
502
Click Calculate.
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Steady-State Case Setup
7.
Check the mass imbalance for the inlet and outlet to confirm there is not a large difference.
Results → Reports → Fluxes...
8.
a.
Select pressure-inlet and pressure-outlet from the list of Boundaries.
b.
Click Compute and close the Flux Reports dialog box.
Save the steady-state case and data files (overset-pod-steady-state.cas.h5 and
overset-pod-steady-state.dat.h5).
File → Write → Case & Data...
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Click OK in the Information dialog box that appears.
12.7. Unsteady Setup
In this section you will define the transient settings.
12.7.1. General Settings
1.
Select Transient in the General task page (Solver group box, under Time).
Setup →
2.
General → Transient
Set the Operating Conditions.
Physics → Solver → Operating Conditions...
3.
a.
Enable Gravity.
b.
Enter -9.81 for Y.
Click OK to confirm the operating conditions.
12.7.2. Compile the UDF
User-Defined → User-Defined → Functions → Compiled...
504
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Unsteady Setup
1.
Click Add... to open the Select File dialog box.
2.
Select property.c and click OK.
3.
Click Build to build the library.
4.
Click OK to close the Question dialog box that appears.
Note:
This UDF contains the mass of the pod and its moments of inertia.
ANSYS Fluent sets up the directory structure and compiles the code. You can see the compilation in
the console window.
5.
Click Load to load the library.
12.7.3. Dynamic Mesh Settings
In this section you will specify the six degrees of freedom (Six DOF) and dynamic mesh settings.
Domain → Mesh Models → Dynamic Mesh...
1.
Enable Dynamic Mesh.
2.
Disable Smoothing.
3.
Enable Six DOF.
4.
Click Settings... to open the Options dialog box.
5.
a.
Enable Write Motion History.
b.
Enter pod-motion for the File Name.
c.
Click OK to confirm the settings.
Set up the moving zones.
a.
Create the dynamic zone for the component
i.
Click Create/Edit... in the Dynamic Mesh task page to open the Dynamic Mesh Zones
dialog box.
ii.
Select component from the Zone Names drop-down list.
iii.
Retain the selection of Rigid Body for Type.
iv.
Retain the selection of On in the Six DOF group box.
v.
Enable Passive in the Six DOF group box.
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vi.
Enter 7.6 for X and 18.5 for Y in the Center of Gravity Location group box.
vii. Click Create to create the dynamic zone for the component.
Note:
The UDF is automatically selected in the Six DOF UDF/Properties drop-down
list. If there were additional UDFs loaded, then you would have to select the
correct one.
b.
506
Create the dynamic zone for the pod.
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Unsteady Setup
i.
Select wall-pod from the Zone Names drop-down list.
ii.
Retain the selection of Rigid Body for Type.
iii.
Retain the selection of On and disable Passive in the Six DOF group box.
iv.
Retain the values for Center of Gravity Location.
v.
Click Create to create the dynamic zone for the pod.
vi.
Close the Dynamic Mesh Zones dialog box.
12.7.4. Report Generation for Unsteady Case
Create a new drag report definition named unsteady_pod for the drag coefficient on the wall-pod.
Solution → Reports → Definitions → New → Force Report → Drag...
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1.
Enter unsteady-pod-drag for Name.
2.
Enable Report File and Report Plot in the Create group box.
3.
Select wall-pod from the Wall Zones list.
4.
Click OK to create the report.
Note that the drag report definition created previously, report-def-0 for the steady state simulaiton
should be deleted. If not a Warning Message appears in the console notifying you that Data for the
following Report File can be wriiten to its file..
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Unsteady Setup
You can click Yes in the Warning Message to create a new report file.
12.7.5. Run Calculations for Unsteady Case
Solution → Run Calculation → Run Calculation...
•
a.
Enter 0.001 for Time Step Size (s).
b.
Enter 1000 for Number of Time Steps.
c.
Enter 8 for Max Iterations/Time Step.
d.
Start recording the transcript.
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File → Write → Start Transcript...
Enter a name for the transcript file.
e.
Click Calculate.
the simulation can take several hours depending on the compute capacity being utilized.
f.
Stop recording the transcript.
File → Write → Stop Transcript...
•
g.
Save the case and data files (overset-pod-transient.cas.h5 and overset-podtransient.dat.h5).
File → Write → Case & Data...
12.7.6. Overset Solution Checking
Check overset solution.
Open the transcript file and look for the warning of:
dead->solve cells
Ideally, no cells should go directly from being dead cells to being solve cells. A large number of cells
directly converting from dead to solve can affect the accuracy of the solution or cause divergence. If
you find that there is a large number of cells that went directly from dead to solve, then you can reduce
the time step size to decrease the likelihood of this issue occurring. If there are any dead to solve
cells present for this calculation run, the warning is printed as shown below:
WARNING: 1 overset dead->solve cells in interface overset-interface
Note:
Objects move their position with time in transient overset moving mesh cases, requiring
dead cells to convert into solve cells. Dead cells do not have proper solution data, so they
need to convert to receptor cells to get the required solution information before converting
to solve cells. If a dead cell converts directly into a solve cell, it may lack required information and cause an improper result. Refer to "Diagnosing Overset Interface Issues" in the
Fluent User's Guide for additional information.
12.7.7. Postprocessing
1.
Create contours of static pressure.
Results → Graphics → Contours → New...
a.
510
Enter contour-pressure for Contour Name.
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Unsteady Setup
b.
Select Banded from the Coloring drop-down list.
c.
Ensure Pressure... and Static Pressure are selected from the Contours of drop-down lists.
d.
De-select all surfaces in the list of Surfaces.
e.
Click Save/Display.
f.
Close the Contours dialog box.
Note:
To capture intermediate images, you can create an animation definition prior to
beginning the calculation. This would allow you to view the individual image
files as well as an animation of the pod as it falls. For additional information on
creating animation definitions, see Animating the Solution in the Fluent User’s
Guide.
2.
Save the case file (overset-pod-transient.cas.h5).
File → Write → Case & Data...
3.
Plot the center of gravity motion of the pod.
a.
Read the pod-motion file into Microsoft Excel and plot flow time vs CG-orientation of
the pod.
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b.
512
Plot flow time vs CG-angular orientation of the pod.
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Unsteady Setup
12.7.8. Diagnosing an Overset Case
Once an overset interface is created, it is important to check and diagnose it. In this section you will
learn about diagnosing an overset interface and about the different cells participating in the solution.
In overset meshing all meshes are categorized into five cell types:
• Solve – (yellow in figures Figure 12.3: Cell Marking on component (p. 517) & Figure 12.4: Cell
Marking on fluid-background (p. 518)) cells that take part in the solution.
• Donor – (marked red in figures Figure 12.3: Cell Marking on component (p. 517) & Figure 12.4: Cell
Marking on fluid-background (p. 518)) provide information to corresponding cell zones.
• Receptor – (marked blue in figures Figure 12.3: Cell Marking on component (p. 517) & Figure 12.4: Cell Marking on fluid-background (p. 518)) receive information from donor cells in the
corresponding cell zones.
• Dead – (marked in red in figures Figure 12.5: Dead Cells in the Component (p. 519)) deactivated
cells located in regions of overlap between the background and component meshes, where
multiple cells are present in the same exact location. Only one set of cells in a region is allowed
to take part in the solution. Additionally, cells outside of the flow regime are marked as dead.
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• Orphan – receptor cells that cannot find a corresponding donor cell. Although Fluent has intelligence to deal with orphan cells, their presence should be avoided to reduce the risk of
solution inaccuracies and divergence.
You can mark orphan cells using the TUI command:
define/overset-interfaces/mark-cells orphan no
This will show all of the orphan cells present in the case, unless you specify a particular zone. Marking
orphan cells creates a register that you can display via the define/overset-interfaces/display-cells text command. The marked cells are in the overset-orphan-cells-r0 register.
In this case there are not any orphan cells, so nothing is displayed in the graphics window. If you
mark solve cells or other cells types and display those registers, then it will appear in the graphics
window.
If large number of orphan cells are generated in a case, then it is advisable to modify the mesh accordingly.
Different type of cells can also be displayed creating contours of Cell Info and displaying the Overset
Cell Type for given surfaces.
Enable the following TUI command to include receptor cells in the contours display:
/define/overset-interfaces/options/render-receptor-cells? yes
The overset interface for this tutorial is created properly, but issues could arise during overset interface
creation for geometries with complex topology. ANSYS Fluent provides options to diagnose issues
and fix them. You can use the ‘debug hole cut’ option to understand more about flood filling of seed
cells or leakage between overlapping boundaries. For detailed information on overset mesh diagnosis,
refer to "Diagnosing Overset Interface Issues" in the Fluent User's Guide.
1.
Start a new Fluent session, and read overset-pod-steady-state.cas.h5 and oversetpod-steady-state.dat.h5.
File → Read → Case & Data...
2.
Create zone surfaces for component and fluid-background.
Results → Surface → Create → Zone...
514
a.
Select component in the Zone list.
b.
Retain component for New Surface Name and click Create.
c.
Similarly, create a zone surface for fluid-background.
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Unsteady Setup
d.
Close the Zone Surface dialog box.
3.
Enter the following TUI command in the console:/define/overset-interfaces/options/render-receptor-cells? Yes
4.
Display contours of the overset cell type on the surface you just created.
Results → Graphics → Contours → New...
a.
Enter contour-overset-1 for Contour Name.
b.
Disable Auto Range (which enables Clip to Range) in the Options group box.
c.
Disable Node Values and Global Range in the Options group box.
d.
Select Cell Info... and Overset Cell Type from the Contours of drop-down lists.
e.
Enter -0.5 for Min and 2.5 for Max.
Note:
Table 12.1: Meaning of Values
Cell Type
Integer Function Value
Donor
2
Solve
1
Receptor
0
Orphan
-1
Dead
-2
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Dead cells cannot be displayed in contours.
f.
516
Click Colormap Options... to open the Colormap dialog box.
i.
Enter 3 for Colormap Size in the Colormap group box.
ii.
Click Apply and close the Colormap dialog box.
g.
Select component from the list of Surfaces.
h.
Click Save/Display and close the Contours dialog box.
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Unsteady Setup
Figure 12.3: Cell Marking on component
i.
Repeat the process for fluid-background.
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Figure 12.4: Cell Marking on fluid-background
5.
Marking and displaying dead cells.
a.
Expand Cell Zones in the tree to check the id number.
Setup → Cell Zone Conditions → Fluid
518
b.
Mark dead cells in component with the following TUI command: define/overset-interfaces/mark-cells dead yes 29
c.
Mark dead cells in fluid-background with the following TUI command: /define/oversetinterfaces/mark-cells dead yes 7
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Unsteady Setup
d.
Display the dead cells by entering the define/overset-interfaces/display-cells
text command in the console.
i.
Enter 0 for the text command prompt to display the overset-dead-cells-componentr0 register (you can enter 0 instead of typing the full name of the register).
Figure 12.5: Dead Cells in the Component
ii.
Enter 1 for the text command prompt to display only the overset-dead-cells-fluidbackground-r1 register.
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Figure 12.6: Dead Cells in the Background
12.8. Summary
In this tutorial, you have learned about overset meshing in ANSYS Fluent and its setup along with best
practices, by solving a store separation problem. You have also learned a few diagnostic techniques for
overset meshing and the postprocessing of results for a store separation case.
520
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Chapter 13: Modeling Species Transport and Gaseous
Combustion
This tutorial is divided into the following sections:
13.1. Introduction
13.2. Prerequisites
13.3. Problem Description
13.4. Background
13.5. Setup and Solution
13.6. Summary
13.7. Further Improvements
13.1. Introduction
This tutorial examines the mixing of chemical species and the combustion of a gaseous fuel.
A cylindrical combustor burning methane (
ANSYS Fluent.
) in air is studied using the eddy-dissipation model in
This tutorial demonstrates how to do the following:
• Enable physical models, select material properties, and define boundary conditions for a turbulent
flow with chemical species mixing and reaction.
• Initiate and solve the combustion simulation using the pressure-based solver.
• Examine the reacting flow results using graphics.
• Predict thermal and prompt NOx production.
• Use custom field functions to compute NO parts per million.
13.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
To learn more about chemical reaction modeling, see the Fluent User's Guide and the Fluent Theory
Guide. Otherwise, no previous experience with chemical reaction or combustion modeling is assumed.
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Modeling Species Transport and Gaseous Combustion
13.3. Problem Description
The cylindrical combustor considered in this tutorial is shown in Figure 13.1: Combustion of Methane
Gas in a Turbulent Diffusion Flame Furnace (p. 522). The flame considered is a turbulent diffusion flame.
A small nozzle in the center of the combustor introduces methane at 80
. Ambient air enters the
combustor coaxially at 0.5
. The overall equivalence ratio is approximately 0.76 (approximately 28
excess air). The high-speed methane jet initially expands with little interference from the outer wall,
and entrains and mixes with the low-speed air. The Reynolds number based on the methane jet diameter
is approximately
.
Figure 13.1: Combustion of Methane Gas in a Turbulent Diffusion Flame Furnace
13.4. Background
In this tutorial, you will use the generalized eddy-dissipation model to analyze the methane-air combustion system. The combustion will be modeled using a global one-step reaction mechanism, assuming
complete conversion of the fuel to
and
. The reaction equation is
(13.1)
This reaction will be defined in terms of stoichiometric coefficients, formation enthalpies, and parameters
that control the reaction rate. The reaction rate will be determined assuming that turbulent mixing is
the rate-limiting process, with the turbulence-chemistry interaction modeled using the eddy-dissipation
model.
13.5. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
13.5.1. Preparation
13.5.2. Mesh
13.5.3. General Settings
13.5.4. Models
13.5.5. Materials
13.5.6. Boundary Conditions
13.5.7. Initial Reaction Solution
13.5.8. Postprocessing
13.5.9. NOx Prediction
522
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Setup and Solution
13.5.1. Preparation
To prepare for running this tutorial:
1.
Download the species_transport.zip file here.
2.
Unzip species_transport.zip to your working directory.
The mesh file gascomb.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
13.5.2. Mesh
1. Read the mesh file gascomb.msh.
File → Read → Mesh...
13.5.3. General Settings
1. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and will report the progress in the console. Ensure
that the reported minimum volume reported is a positive number.
2. Scale the mesh.
Domain → Mesh → Scale...
Since this mesh was created in units of millimeters, you will need to scale the mesh into meters.
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Modeling Species Transport and Gaseous Combustion
a. Select mm from the Mesh Was Created In drop-down list in the Scaling group box.
b. Click Scale.
c. Ensure that m is selected from the View Length Unit In drop-down list.
d. Ensure that Xmax and Ymax are reset to 1.8 m and 0.225 m respectively.
The default SI units will be used in this tutorial, hence there is no need to change any units in this
problem.
e. Close the Scale Mesh dialog box.
f.
Right click in the graphics window and select Refresh Display
g. Clicking the Fit to Window icon,
the window.
, will cause the object to fit exactly and be centered in
3. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
Note:
You should check the mesh after you manipulate it (scale, convert to polyhedra, merge,
separate, fuse, add zones, or smooth and swap). This will ensure that the quality of the
mesh has not been compromised.
4. Examine the mesh with the default settings.
524
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Setup and Solution
Figure 13.2: The Quadrilateral Mesh for the Combustor Model
Extra:
You can use the right mouse button to probe for mesh information in the graphics
window. If you click the right mouse button on any node in the mesh, information will
be displayed in the ANSYS Fluent console about the associated zone, including the
name of the zone. This feature is especially useful when you have several zones of the
same type and you want to distinguish between them quickly.
5. Select Axisymmetric in the 2D Space list.
Setup → General
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Modeling Species Transport and Gaseous Combustion
13.5.4. Models
1. Enable heat transfer by enabling the energy equation.
Physics → Models → Energy
2. Retain the default k-ω SST turbulence model.
Physics → Models → Viscous...
526
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Setup and Solution
a. Retain the default settings for the k-omega model.
b. Click OK to close the Viscous Model dialog box.
3. Enable chemical species transport and reaction.
Physics → Models → Species...
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Modeling Species Transport and Gaseous Combustion
a. Select Species Transport in the Model list.
The Species Model dialog box will expand to provide further options for the Species Transport
model.
b. Enable Volumetric in the Reactions group box.
c. Select methane-air from the Mixture Material drop-down list.
Scroll down the list to find methane-air.
Note:
The Mixture Material list contains the set of chemical mixtures that exist in the
ANSYS Fluent database. You can select one of the predefined mixtures to access a
complete description of the reacting system. The chemical species in the system
and their physical and thermodynamic properties are defined by your selection of
the mixture material. You can alter the mixture material selection or modify the
mixture material properties using the Create/Edit Materials dialog box (see Materials (p. 529)).
528
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Setup and Solution
d. Select Eddy-Dissipation in the Turbulence-Chemistry Interaction group box.
The eddy-dissipation model computes the rate of reaction under the assumption that chemical
kinetics are fast compared to the rate at which reactants are mixed by turbulent fluctuations (eddies).
e. Click OK to close the Species Model dialog box.
f.
Click OK to close the Information dialog box that describes solver relaxation setting changes.
Prior to listing the properties that are required for the models you have enabled, ANSYS Fluent will
display a warning about the symmetry zone in the console. You may have to scroll up to see this
warning.
Warning: It appears that symmetry zone 5 should actually be an axis
(it has faces with zero area projections).
Unless you change the zone type from symmetry to axis,
you may not be able to continue the solution without
encountering floating point errors.
In the axisymmetric model, the boundary conditions should be such that the centerline is an axis type
instead of a symmetry type. You will change the symmetry zone to an axis boundary in Boundary
Conditions (p. 532).
13.5.5. Materials
In this step, you will examine the default settings for the mixture material. This tutorial uses mixture
properties copied from the Fluent Database. In general, you can modify these or create your own mixture
properties for your specific problem as necessary.
1. Confirm the properties for the mixture materials.
Setup → Materials → Mixture → methane-air
Edit...
The Create/Edit Materials dialog box will display the mixture material (methane-air) that was selected
in the Species Model dialog box. The properties for this mixture material have been copied from the
Fluent Database... and will be modified in the following steps.
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Modeling Species Transport and Gaseous Combustion
a. Click the Edit... button to the right of the Mixture Species drop-down list to open the Species
dialog box.
530
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Setup and Solution
You can add or remove species from the mixture material as necessary using the Species dialog
box.
i.
Retain the default selections from the Selected Species selection list.
The species that make up the methane-air mixture are predefined and require no modification.
ii. Click OK to close the Species dialog box.
b. Click the Edit... button to the right of the Reaction drop-down list to open the Reactions
dialog box.
The eddy-dissipation reaction model ignores chemical kinetics (the Arrhenius rate) and uses only
the parameters in the Mixing Rate group box in the Reactions dialog box. The Arrhenius Rate
group box will therefore be inactive. The values for Rate Exponent and Arrhenius Rate parameters
are included in the database and are employed when the alternate finite-rate/eddy-dissipation
model is used.
i.
Retain the default values in the Mixing Rate group box.
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ii. Click OK to close the Reactions dialog box.
c. Retain the selection of incompressible-ideal-gas from the Density drop-down list.
d. Retain the selection of mixing-law from the Cp (Specific Heat) drop-down list.
e. Retain the default values for Thermal Conductivity, Viscosity, and Mass Diffusivity.
f.
Click Change/Create to accept the material property settings.
g. Close the Create/Edit Materials dialog box.
The calculation will be performed assuming that all properties except density and specific heat are
constant. The use of constant transport properties (viscosity, thermal conductivity, and mass diffusivity
coefficients) is acceptable because the flow is fully turbulent. The molecular transport properties will
play a minor role compared to turbulent transport.
13.5.6. Boundary Conditions
1. Convert the symmetry zone to the axis type.
Setup → Boundary Conditions → Symmetry → symmetry-5
Type
axis
The symmetry zone must be converted to an axis to prevent numerical difficulties where the radius
reduces to zero.
2. Set the boundary conditions for the air inlet (velocity-inlet-8).
Setup → Boundary Conditions → Inlet → velocity-inlet-8
Edit...
To determine the zone for the air inlet, display the mesh without the fluid zone to see the boundaries.
Use the right mouse button to probe the air inlet. ANSYS Fluent will report the zone name (velocityinlet-8) in the console.
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Setup and Solution
a. Enter air-inlet for Zone Name.
This name is more descriptive for the zone than velocity-inlet-8.
b. Enter 0.5
for Velocity Magnitude.
c. Select Intensity and Hydraulic Diameter from the Specification Method drop-down list in
the Turbulence group box.
d. Enter 10
e. Enter 0.44
f.
for Turbulent Intensity.
for Hydraulic Diameter.
Click the Thermal tab and retain the default value of 300
for Temperature.
g. Click the Species tab and enter 0.23 for o2 in the Species Mass Fractions group box.
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h. Click Apply and close the Velocity Inlet dialog box.
3. Set the boundary conditions for the fuel inlet (velocity-inlet-6).
Setup → Boundary Conditions → Inlet → velocity-inlet-6
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Setup and Solution
a. Enter fuel-inlet for Zone Name.
This name is more descriptive for the zone than velocity-inlet-6.
b. Enter 80
for the Velocity Magnitude.
c. Select Intensity and Hydraulic Diameter from the Specification Method drop-down list in
the Turbulence group box.
d. Enter 10
e. Enter 0.01
f.
for Turbulent Intensity.
for Hydraulic Diameter.
Click the Thermal tab and retain the default value of 300
for Temperature.
g. Click the Species tab and enter 1 for ch4 in the Species Mass Fractions group box.
h. Click Apply and close the Velocity Inlet dialog box.
4. Set the boundary conditions for the exit boundary (pressure-outlet-9).
Setup → Boundary Conditions → Outlet → pressure-outlet-9
Edit...
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a. Retain the default value of 0
for Gauge Pressure.
b. Select Intensity and Hydraulic Diameter from the Specification Method drop-down list in
the Turbulence group box.
c. Enter 10
d. Enter 0.45
for Backflow Turbulent Intensity.
for Backflow Hydraulic Diameter.
e. Click the Thermal tab and retain the default value of 300
f.
for Backflow Total Temperature.
Click the Species tab and enter 0.23 for o2 in the Backflow Species Mass Fractions group
box.
g. Click Apply and close the Pressure Outlet dialog box.
The Backflow values in the Pressure Outlet dialog box are utilized only when backflow occurs at the
pressure outlet. Always assign reasonable values because backflow may occur during intermediate iterations and could affect the solution stability.
5. Set the boundary conditions for the outer wall (wall-7).
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Setup and Solution
Setup → Boundary Conditions → Wall → wall-7
Edit...
Use the mouse-probe method described for the air inlet to determine the zone corresponding to the
outer wall.
a. Enter outer-wall for Zone Name.
This name is more descriptive for the zone than wall-7.
b. Click the Thermal tab.
i.
Select Temperature in the Thermal Conditions list.
ii. Retain the default value of 300
for Temperature.
c. Click Apply and close the Wall dialog box.
6. Set the boundary conditions for the fuel inlet nozzle (wall-2).
Setup → Boundary Conditions → Wall → wall-2
Edit...
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a. Enter nozzle for Zone Name.
This name is more descriptive for the zone than wall-2.
b. Click the Thermal tab.
i.
Retain the default selection of Heat Flux in the Thermal Conditions list.
ii. Retain the default value of 0
for Heat Flux, so that the wall is adiabatic.
c. Click Apply and close the Wall dialog box.
13.5.7. Initial Reaction Solution
You will first calculate a solution for the basic reacting flow neglecting pollutant formation. In a later step,
you will perform an additional analysis to simulate NOx.
1.
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Setup and Solution
Retain the default selections.
2. Ensure the plotting of residuals during the calculation.
Solution → Reports → Residuals...
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a. Ensure that Plot is enabled in the Options group box.
b. Click OK to close the Residual Monitors dialog box.
3. Initialize the field variables.
Solution → Initialization
a. Retain the default Hybrid initialization method and click Initialize to initialize the variables.
4. Save the case file (gascomb1.cas.h5).
File → Write → Case...
a. Enter gascomb1.cas.h5 for Case File.
b. Ensure that Write Binary Files is enabled to produce a smaller, unformatted binary file.
c. Click OK to close the Select File dialog box.
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Setup and Solution
5. Run the calculation by requesting 200 iterations.
Solution → Run Calculation → Run Calculation...
a. Enter 5 for the Timescale Factor.
The Timescale Factor allows you to further manipulate the computed Time Step calculated by ANSYS
Fluent. Larger time steps can lead to faster convergence. However, if the time step is too large it
can lead to solution instability.
b. Enter 200 for Number of Iterations.
c. Click Calculate.
6. Save the case and data files (gascomb1.cas.h5 and gascomb1.dat.h5).
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File → Write → Case & Data...
Note:
If you choose a file name that already exists in the current folder, ANSYS Fluent will
ask you to confirm that the previous file is to be overwritten.
13.5.8. Postprocessing
Review the solution by examining graphical displays of the results and performing surface integrations at
the combustor exit.
1. Report the total sensible heat flux.
Results → Reports → Fluxes...
a. Select Total Sensible Heat Transfer Rate in the Options list.
b. Select all the boundaries from the Boundaries selection list (you can click the select-all button
).
c. Click Compute and close the Flux Reports dialog box.
Note:
The energy balance is good because the net result is small compared to the heat
of reaction.
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Setup and Solution
2. Display filled contours of temperature (Figure 13.3: Contours of Temperature (p. 543)).
Results → Graphics → Contours → New...
a. Enter contour-temp for Contour Name.
b. Ensure that Filled is enabled in the Options group box.
c. Select Banded in the Coloring group box.
d. Select Temperature... and Static Temperature in the Contours of drop-down lists.
e. Click Save/Display and close the Contours dialog box.
Figure 13.3: Contours of Temperature
The peak temperature is approximately 2300
.
3. Display velocity vectors (Figure 13.4: Velocity Vectors (p. 545)).
Results → Graphics → Vectors → New...
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a. Enter vector-vel for Vector Name.
b. Select arrow from the Style drop-down list.
c. Enter 0.01 for Scale.
d. Click the Vector Options... button to open the Vector Options dialog box.
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Setup and Solution
i.
Enable Fixed Length.
The fixed length option is useful when the vector magnitude varies dramatically. With fixed
length vectors, the velocity magnitude is described only by color instead of by both vector length
and color.
ii. Enter 0.1 for Scale Head.
iii. Click Apply and close the Vector Options dialog box.
e. Click Save/Display and close the Vectors dialog box.
The entrainment of air into the high-velocity methane jet is clearly visible.
Figure 13.4: Velocity Vectors
4. Display filled contours of mass fraction for
(Figure 13.5: Contours of CH4 Mass Fraction (p. 546)).
Results → Graphics → Contours → New...
a. Enter contour-ch4-mass-fraction for Contour Name.
b. Select Banded in the Coloring group box.
c. Select Species... and Mass fraction of ch4 from the Contours of drop-down lists.
d. Click Save/Display and close the Contours dialog box.
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Figure 13.5: Contours of CH4 Mass Fraction
5. In a similar manner, display the contours of mass fraction for the remaining species ,
, and
(Figure 13.6: Contours of O2 Mass Fraction (p. 546), Figure 13.7: Contours of CO2 Mass Fraction (p. 547), and Figure 13.8: Contours of H2O Mass Fraction (p. 547)).
Figure 13.6: Contours of O2 Mass Fraction
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Setup and Solution
Figure 13.7: Contours of CO2 Mass Fraction
Figure 13.8: Contours of H2O Mass Fraction
6. Determine the average exit temperature.
Results → Reports → Surface Integrals...
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a. Select Mass-Weighted Average from the Report Type drop-down list.
b. Select Temperature... and Static Temperature from the Field Variable drop-down lists.
The mass-averaged temperature will be computed as:
(13.2)
c. Select pressure-outlet-9 from the Surfaces selection list, so that the integration is performed
over this surface.
d. Click Compute.
The Mass-Weighted Average field will show that the exit temperature is approximately 1841
7. Determine the average exit velocity.
Results → Reports → Surface Integrals...
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.
Setup and Solution
a. Select Area-Weighted Average from the Report Type drop-down list.
b. Select Velocity... and Velocity Magnitude from the Field Variable drop-down lists.
The area-weighted velocity-magnitude average will be computed as:
(13.3)
c. Click Compute.
The Area-Weighted Average field will show that the exit velocity is approximately 3.31
.
d. Close the Surface Integrals dialog box.
8. Save the case file (gascomb1.cas.h5).
File → Write → Case...
13.5.9. NOx Prediction
In this section you will extend the ANSYS Fluent model to include the prediction of NOx. You will first calculate the formation of both thermal and prompt NOx, then calculate each separately to determine the
contribution of each mechanism.
1. Enable the NOx model.
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Modeling Species Transport and Gaseous Combustion
Setup → Models → Species → NOx
Edit...
a. Enable Thermal NOx and Prompt NOx in the Pathways group box.
b. Select ch4 from the Fuel Species selection list.
c. Click the Turbulence Interaction Mode tab.
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Setup and Solution
i.
Select temperature from the PDF Mode drop-down list.
This will enable the turbulence-chemistry interaction. If turbulence interaction is not enabled,
you will be computing NOx formation without considering the important influence of turbulent
fluctuations on the time-averaged reaction rates.
ii. Retain the default selection of beta from the PDF Type drop-down list and enter 20 for
PDF Points.
The value for PDF Points is increased from 10 to 20 to obtain a more accurate NOx prediction.
iii. Select transported from the Temperature Variance drop-down list.
d. Select partial-equilibrium from the [O] Model drop-down list in the Formation Model
Parameters group box in the Thermal tab.
The partial-equilibrium model is used to predict the O radical concentration required for thermal
NOx prediction.
e. Click the Prompt tab.
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i.
Retain the default value of 1 for Fuel Carbon Number.
ii. Enter 0.76 for Equivalence Ratio.
All of the parameters in the Prompt tab are used in the calculation of prompt NOx formation.
The Fuel Carbon Number is the number of carbon atoms per molecule of fuel. The Equivalence
Ratio defines the fuel-air ratio (relative to stoichiometric conditions).
f.
Click Apply to accept these changes and close the NOx Model dialog box.
2. Enable the calculation of NO species only and temperature variance.
Solution → Controls → Equations...
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Setup and Solution
a. Deselect all variables except Pollutant no and Temperature Variance from the Equations
selection list.
b. Click OK to close the Equations dialog box.
You will predict NOx formation in a postprocessing mode, with the flow field, temperature, and
hydrocarbon combustion species concentrations fixed. Hence, only the NO equation will be computed. Prediction of NO in this mode is justified on the grounds that the NO concentrations are
very low and have negligible impact on the hydrocarbon combustion prediction.
3. Confirm the convergence criterion for the NO species equation.
Solution → Reports → Residuals...
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Modeling Species Transport and Gaseous Combustion
a. Ensure that the Absolute Criteria for pollut_no is set to 1e-06.
b. Click OK to close the Residual Monitors dialog box.
4. Request 25 more iterations.
Solution → Run Calculation
5. Save the new case and data files (gascomb2.cas.h5 and gascomb2.dat.h5).
File → Write → Case & Data...
6. Review the solution by creating and displaying a contour definition for NO mass fraction (Figure 13.9: Contours of NO Mass Fraction — Prompt and Thermal NOx Formation (p. 555)).
Results → Graphics → Contours → New...
a. Enter contour-no-mass-fraction for Contour Name.
b. Disable Filled in the Options group box.
c. Select NOx... and Mass fraction of Pollutant no from the Contours of drop-down lists.
d. Click Save/Display and close the Contours dialog box.
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Setup and Solution
Figure 13.9: Contours of NO Mass Fraction — Prompt and Thermal NOx Formation
7. Calculate the average exit NO mass fraction.
Results → Reports → Surface Integrals...
a. Select Mass-Weighted Average from the Report Type drop-down list.
b. Select NOx... and Mass fraction of Pollutant no from the Field Variable drop-down lists.
c. Ensure that pressure-outlet-9 is selected from the Surfaces selection list.
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d. Click Compute.
The Mass-Weighted Average field will show that the exit NO mass fraction is approximately
0.00445.
e. Close the Surface Integrals dialog box.
8. Save the case file (gascomb2.cas.h5).
File → Write → Case...
9. Disable the prompt NOx mechanism in preparation for solving for thermal NOx only.
Setup → Models → Species → NOx
Edit...
a. In the Formation tab, disable Prompt NOx.
b. Click Apply and close the NOx Model dialog box.
10. Request 25 iterations.
Solution → Run Calculation
11. Review the thermal NOx solution by displaying the contour-no-mass-fraction contour definition
for NO mass fraction (under the Results/Graphics/Contours tree branch) you created earlier
(Figure 13.10: Contours of NO Mass Fraction—Thermal NOx Formation (p. 556)).
Results → Graphics → Contours → contour-no-mass-fraction
Display
Figure 13.10: Contours of NO Mass Fraction—Thermal NOx Formation
Note that the concentration of NO is slightly lower without the prompt NOx mechanism.
12. Compute the average exit NO mass fraction with only thermal NOx formation.
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Setup and Solution
Results → Reports → Surface Integrals...
Tip:
Follow the same procedure you used earlier for the calculation with both thermal
and prompt NOx formation.
The Mass-Weighted Average field will show that the exit NO mass fraction with only thermal NOx
formation (without prompt NOx formation) is approximately 0.00441.
13. Save the new case and data files (gascomb2-thermal.cas.h5 and gascomb2thermal.dat.h5).
File → Write → Case & Data...
14. Solve for prompt NOx production only.
Setup → Models → Species → NOx
Edit...
a. Disable Thermal NOx in the Pathways group box.
b. Enable Prompt NOx.
c. Click Apply and close the NOx Model dialog box.
15. Request 25 iterations.
Solution → Run Calculation
16. Review the prompt NOx solution by displaying the contour-no-mass-fraction contour definition
for NO mass fraction (under the Results/Graphics/Contours tree branch) (Figure 13.11: Contours
of NO Mass Fraction—Prompt NOx Formation (p. 558)).
Results → Graphics → Contours → contour-no-mass-fraction
Display
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Figure 13.11: Contours of NO Mass Fraction—Prompt NOx Formation
The prompt NOx mechanism is most significant in fuel-rich flames. In this case the flame is lean and
prompt NO production is low.
17. Compute the average exit NO mass fraction only with prompt NOx formation.
Results → Reports → Surface Integrals...
Tip:
Follow the same procedure you used earlier for the calculation with both thermal
and prompt NOx formation.
The Mass-Weighted Average field will show that the exit NO mass fraction with only prompt
NOx formation is approximately 9.87e-05
Note:
The individual thermal and prompt NO mass fractions do not add up to the levels
predicted with the two models combined. This is because reversible reactions are involved. NO produced in one reaction can be destroyed in another reaction.
18. Use a custom field function to compute NO parts per million (ppm).
The NOppm will be computed from the following equation:
(13.4)
Note:
This is the dry ppm. Therefore, the value is normalized by removing the water mole
fraction in the denominator.
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Setup and Solution
User Defined → Field Functions → Custom...
a. Select NOx... and Mole fraction of Pollutant no from the Field Functions drop-down lists,
and click the Select button to enter molef-pollut-pollutant-0 in the Definition field.
b. Click the appropriate calculator buttons to enter
*10ˆ6/(1-
in the Definition field, as shown in the previous dialog box.
Tip:
If you make a mistake, click the DEL button on the calculator pad to delete
the last item you added to the function definition.
c. Select Species... and Mole fraction of h2o from the Field Functions drop-down lists, and
click the Select button to enter molef-h2o in the Definition field.
d. Click the ) button to complete the field function.
e. Enter no-ppm for New Function Name.
f.
Click Define to add the new field function to the variable list and close the Custom Field
Function Calculator dialog box.
19. Display contours of NO ppm (Figure 13.12: Contours of NO ppm — Prompt NOx Formation (p. 560)).
Results → Graphics → Contours → New...
a. Enter contour-no-ppm for Contour Name.
b. Disable Filled in the Options group box.
c. Select Custom Field Functions... and no-ppm from the Contours of drop-down lists.
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Scroll up the list to find Custom Field Functions....
d. Click Save/Display and close the Contours dialog box.
Figure 13.12: Contours of NO ppm — Prompt NOx Formation
The contours closely resemble the mass fraction contours (Figure 13.11: Contours of NO Mass Fraction—Prompt NOx Formation (p. 558)), as expected.
20. Save the new case and data files (gascomb2-prompt.cas.h5 and gascomb2prompt.dat.h5).
File → Write → Case & Data...
13.6. Summary
In this tutorial you used ANSYS Fluent to model the transport, mixing, and reaction of chemical species.
The reaction system was defined by using a mixture-material entry in the ANSYS Fluent database. The
procedures used here for simulation of hydrocarbon combustion can be applied to other reacting flow
systems.
The NOx production in this case was dominated by the thermal NO mechanism. This mechanism is very
sensitive to temperature. Every effort should be made to ensure that the temperature solution is not
overpredicted, since this will lead to unrealistically high predicted levels of NO.
13.7. Further Improvements
Further improvements can be expected by including the effects of intermediate species and radiation,
both of which will result in lower predicted combustion temperatures.
The single-step reaction process used in this tutorial cannot account for the moderating effects of intermediate reaction products, such as CO and . Multiple-step reactions can be used to address these
species. If a multi-step Magnussen model is used, considerably more computational effort is required
to solve for the additional species. Where applicable, the nonpremixed combustion model can be used
to account for intermediate species at a reduced computational cost.
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Further Improvements
For more details on the nonpremixed combustion model, see the Fluent User's Guide.
Radiation heat transfer tends to make the temperature distribution more uniform, thereby lowering the
peak temperature. In addition, radiation heat transfer to the wall can be very significant (especially here,
with the wall temperature set at 300 ). The large influence of radiation can be anticipated by computing
the Boltzmann number for the flow:
where
is the Boltzmann constant (5.729
) and
is the adiabatic flame temperature.
For a quick estimate, assume
,
, and
(the majority of the
inflow is air). Assume
. The resulting Boltzmann number is Bo = 1.09, which shows that
radiation is of approximately equal importance to convection for this problem.
For details on radiation modeling, see the Fluent User's Guide.
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Chapter 14: Using the Monte Carlo Radiation Model
This tutorial is divided into the following sections:
14.1. Introduction
14.2. Prerequisites
14.3. Problem Description
14.4. Setup and Solution
14.5. Summary
14.6. Further Improvements
14.1. Introduction
In this tutorial, radiation and conduction through coupled walls is solved using the Monte Carlo radiation
model to locate and determine the severity of any hotspots generated by the focusing of the sun's rays
through a headlamp lens.
This tutorial demonstrates how to do the following:
• Use the Watertight Geometry guided workflow to:
– Import a CAD geometry
– Generate a surface mesh
– Generate a volume mesh
• Use the Monte Carlo (MC) radiation model.
• Create new materials with thermal and radiation properties
• Set the boundary conditions for a heat transfer problem involving conduction and radiation.
• Calculate a solution using the pressure-based solver.
• Display contours of wall temperature
Related video that demonstrates steps for setting up, solving, and postprocessing the solution results
for a turbulent flow within a manifold:
14.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
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Using the Monte Carlo Radiation Model
14.3. Problem Description
The problem to be considered is the modeling of solar radiation in an automotive headlamp assembly
shown in Problem Description (p. 383). For cars parked in uncovered areas or standing on highways for
long periods of time, solar rays entering the headlamp are focused by the lens in certain areas inside,
producing thermal hot spots. Overall heat up of the assembly and thermal hot spots produce stresses
due to thermal expansion & mechanical constraints. Moreover, thermal hot spots can also possibly harm
electronics or other plastic components (due to melting and/or burning) that are used in the headlamp
assembly.
Figure 14.1: Case Geometry
The headlamp assembly is modelled in an air volume with the boundaries maintained at a temperature
of 25 C. Two walls supply a 1200 w/m^2 heat flux to simulate the effect of the sun's rays shining on
the headlamp. The rays will travel into the headlamp through the front cover (polycarbonate, with an
absorption coefficient of 20 m^-1 and refractive index of 1.586) and be focused by the lens (glass, with
an absorption coefficient of 5.302 m^-1 and refractive index of 1.471).The rest of the components are
modelled as plastic and participate by absorbing, reflecting, and emitting radiation. The rim bezel is
modelled with an emissivity of 0.16, meaning 84% of incident radiation is reflected.
14.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
14.4.1. Preparation
14.4.2. Meshing Workflow
14.4.3. Mesh
14.4.4. Models
14.4.5. Materials
14.4.6. Cell Zone Conditions
14.4.7. Boundary Conditions
14.4.8. Solution
14.4.9. Postprocessing
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Setup and Solution
14.4.1. Preparation
To prepare for running this tutorial:
1.
Download the radiation_headlamp.zip file here.
2.
Unzip radiation_headlamp.zip to your working directory.
The file headlamp.scdoc can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Meshing in the top-left selection list to start Fluent in Meshing Mode.
5.
Disable Double Precision under Options.
6.
Set Meshing Processes and Solver Processes to 4 under Parallel (Local Machine).
14.4.2. Meshing Workflow
1. Start the meshing workflow.
a. In the Workflow tab, select the Watertight Geometry workflow.
b. Review the tasks of the workflow.
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Each task is designated with an icon indicating its state (for example, as complete, incomplete, etc. For more information, see Understanding Task States in the Fluent User's Guide).
All tasks are initially incomplete and you proceed through the workflow completing all
tasks. Additional tasks are also available for the workflow. For more information, see
Customizing Workflows in the Fluent User's Guide.
2. Import the CAD geometry (headlamp.scdoc).
a. Select the Import Geometry task.
b. For File Format, keep the default setting of CAD.
c. For Units, keep the default setting as mm.
d. For File Name, enter the path and file name for the CAD geometry that you want to import
(headlamp.scdoc).
Note:
The workflow only supports *.scdoc (SpaceClaim) and the intermediary *.pmdb
file formats.
e. Select Import Geometry.
This will update the task, display the geometry in the graphics window (Figure 3.2: The Imported
CAD Geometry for the Catalytic Converter (p. 90)), and allow you to proceed onto the next task in
the workflow.
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Setup and Solution
Figure 14.2: The Imported CAD Geometry for the Headlamp
Note:
Alternatively, you can use the ... button next to File Name to locate the CAD geometry file, after which, the Import Geometry task automatically updates, displaying
the geometry in the graphics window, and the workflow automatically progresses
to the next task.
Throughout the workflow, you are able to return to a task and change its settings using either the
Edit button, or the Revert and Edit button. For more information, see Editing Tasks in the Fluent
User's Guide.
3. Add local sizing.
a. In the Add Local Sizing task, you are prompted as to whether or not you would like to add
local sizing controls to the faceted geometry.
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In this tutorial, we will add local sizing in and around the lens, since that is an area where we require
a more refined mesh for the radiation simulation. Later, we will apply settings for a coarser surface
mesh elsewhere.
i.
At the prompt for adding local sizing, select yes.
ii. Enter boi_lens for the Name of the size control.
iii. Specify Body of Influence for the Size Control Type.
iv. Specify 2 for the Target Mesh Size.
v. Select the region for body of influence, boi.
For occasions when the list of items is long, you can use the Filter Text option and use an expression such as in* to show only items starting with "in". Alternatively, you can use the Use
Wildcard option to list and pres-select matching items. See Filtering Lists and Using Wildcards
for more information.
vi. Click Add Local Sizing.
b. In the Add Local Sizing task, you can add additional local sizing controls to the faceted geometry.
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Setup and Solution
You can now see the boi_lens task in the workflow, which can be selected to change its settings.
The Add Local Sizing task can still be used to add more local sizing controls to the geometry.
i.
At the prompt for adding local sizing, select yes.
ii. Enter bodysize_lens for the Name of the size control.
iii. Specify Body Size for the Size Control Type.
iv. Specify 2 for the Target Mesh Size.
v. Select the region for body size, lens.
vi. Click Add Local Sizing to complete this task and proceed to the next task in the workflow.
4. Generate the surface mesh.
a. In the Generate the Surface Mesh task, you can set various properties of the surface mesh
for the faceted geometry.
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b. Specify 3 for the Minimum Size.
c. Specify 40 for the Maximum Size.
Note:
The red boxes displayed on the geometry in the graphics window are a graphical
representation of size settings. These boxes change size as the values change, and
they can be hidden by using the Clear Preview button.
d. Click Generate the Surface Mesh to complete this task and proceed to the next task in the
workflow.
5. Describe the geometry.
When you select the Describe Geometry task, you are prompted with questions relating to the
nature of the imported geometry.
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Setup and Solution
a. Select The geometry consists of both fluid and solid regions and/or voids option under
Geometry Type, since this model contains both fluid and solids, and potential voids.
b. Keep the rest of the default settings for this task.
c. Click Describe Geometry to complete this task and proceed to the next task in the
workflow.
6. Confirm and update the boundaries.
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a. Select the Update Boundaries task, where you can inspect the mesh boundaries and confirm
and change any designated boundaries accordingly. ANSYS Fluent attempts to determine the
correct arrangement of boundaries automatically.
b. The proposed boundary is correct, so click Update Boundaries and proceed to the next task.
7. Create the fluid region.
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Setup and Solution
a. Select the Create Regions task, where you can determine the number of fluid regions that
need to be extracted. ANSYS Fluent attempts to determine the number of fluid regions to
extract automatically.
b. For the Estimated Number of Fluid Regions, keep the default selection of 1.
c. Click Create Regions.
8. Update your regions.
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a. Select the Update Regions task, where you can review and change the tabulated names and
types of the various regions that have been generated from your imported geometry, and
change them as needed.
b. Keep the default settings, and click Update Regions.
9. Add boundary layers.
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Setup and Solution
a. Select the Add Boundary Layers task, where you can set properties of the boundary layer
mesh.
For the Add Boundary Layers task, select no at the prompt as to whether or not you want
to define boundary layer settings.
Since well resolved flows near the walls are not necessary, the exclusion of boundary layers will
simplify the mesh and keep cell counts low.
b. Click Update and proceed to the next task.
10. Generate the volume mesh.
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a. Select the Generate the Volume Mesh task, where you can set properties of the volume mesh
itself.
b. Keep the default settings, and click Generate the Volume Mesh.
ANSYS Fluent will apply your settings and proceed to generate a volume mesh for the manifold
geometry. Once complete, the mesh is displayed in the graphics window and a clipping plane is
automatically inserted with a layer of cells drawn so that you can quickly see the details of the
volume mesh.
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Setup and Solution
11. Check the mesh.
Mesh → Check
12. Save the mesh file (headlamp.msh.gz).
File → Write → Mesh...
13. Switch to Solution mode.
Now that a high-quality mesh has been generated using ANSYS Fluent in meshing mode, you can
now switch to solver mode to complete the set up of the simulation.
We have just checked the mesh, so select Yes when prompted to switch to solution mode.
14.4.3. Mesh
1. Display and examine the mesh.
Domain → Mesh → Display...
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a. Disable Edges in the Options group box.
b. Ensure that all surfaces are selected from the Surfaces selection list.
c. Deselect enclosure:1 and rad-input from the Surfaces selection list.
d. Click Display and close the Mesh Display dialog box.
The graphics display will be updated to show only the headlamp mesh.
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Setup and Solution
Figure 14.3: Graphics Display of Headlamp Mesh
14.4.4. Models
1. Enable the energy equation.
Physics → Models
a. Enable Energy.
2. Enable the laminar viscous model.
Physics → Models → Viscous...
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a. Select Laminar in the Model group box.
b. Click OK to close the Viscous Model dialog box.
3. Set up the Monte Carlo (MC) radiation model.
Physics → Models → Radiation...
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Setup and Solution
a. Select Monte Carlo (MC).
b. Enter 20 for Energy Iterations per Radiation Iteration.
c. Enter 10000000 for Target Number of Histories.
The MC model is a statistical radiation model that tracks a sample of photons through the
system. The size of this sample is determined by Target Number of Histories. In general, the
larger the number of histories, the more accurate the simulation at the expense of compute
time. In this tutorial, a relatively low number is used for demonstration purposes. In practice,
this number may need to be increased to achieve suitable results.
The MC model is preferred in this case because of the collimated beam type irradiation being
modelled. The Discrete Ordinates model would require very high angular discretization and,
therefore, would be computationally expensive. The Surface to Surface model assumes all radiation to be diffuse and so would not capture the specular nature of the focusing of rays by
the lens.
d. Click OK to close the Radiation Model dialog box.
e. Click OK to close the Information dialog box.
14.4.5. Materials
1. Define a new material, glass.
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Physics → Materials → Create/Edit...
a. Select solid from the Material type drop-down list.
b. Clear the entry in the Chemical Formula field.
c. Configure the following properties for glass:
Field
Setting
Name
glass
Density
2650 kg/m3
Cp (Specific Heat)
1887 j/kg-k
Thermal Conductivity
7.6 w/m-k
Absorption Coefficient
5.302 m^-1
Refractive Index
1.4714
d. Click Change/Create and select Yes to overwrite aluminum, since it will not be used in this
case.
2. Define a new material, plastic.
Physics → Materials → Create/Edit...
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Setup and Solution
a. Configure the following properties for plastic:
Field
Setting
Name
plastic
Density
1545.3 kg/m3
Cp (Specific Heat)
2302 j/kg-k
Thermal Conductivity
0.316 w/m-k
Absorption Coefficient
0
Refractive Index
1
b. Click Change/Create and select No to retain glass.
3. Close the Create/Edit Materials dialog box.
14.4.6. Cell Zone Conditions
1. Set the cell zone conditions for the bezel.
Setup → Cell Zone Conditions → Solid → bezel
Edit...
a. Select plastic from the Material Name drop-down list.
b. Click Apply and close the Solid dialog box.
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2. Copy the cell zone conditions for bezel to holder, housing, inner-bezel, reflector, rim-bezel, and
seating-steel-rim.
Setup → Cell Zone Conditions → Solid → bezel
Copy...
a. Ensure bezel is selected in the From Cell Zone list.
b. In the To Cell Zones list, select holder, housing, inner-bezel, reflector, rim-bezel, and
seating-steel-rim.
c. Click Copy.
d. Click OK when prompted to confirm.
e. Close the Copy Conditions dialog box.
3. Set the cell zone conditions for the lens.
Setup → Cell Zone Conditions → Solid → lens
Edit...
a. Ensure glass is selected from the Material Name drop-down list.
b. Enable Participates in Radiation.
c. Click Apply and close the Solid dialog box.
14.4.7. Boundary Conditions
The mesh has a large number of faces and several have the suffix "-shadow". These are automatically
generated in Fluent because the faces are two-sided, meaning every face has two separate boundaries,
one for each side. You will utilize the copy function used in setting up the cell zone conditions to aide in
this section.
1. Set the basic boundary conditions for all boundaries:
Setup → Boundary Conditions → Wall → bezel-enclosure
Tab
Setting
Edit...
Value
Thermal
Material name
plastic
Radiation
BC Type
opaque
Internal Emissivity
1
Diffuse Fraction
1
Click Apply and close the Wall dialog box.
2. Copy the boundary conditions for bezel-enclosure to all other boundaries.
Setup → Boundary Conditions → Wall → bezel-enclosure
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Setup and Solution
a. Ensure bezel-enclosure is selected in the From Boundary Zone list.
b. Click Select All Shown (
) to select all boundaries in the To Boundary Zones list.
c. Click Copy.
d. Click OK when prompted to confirm.
e. Close the Copy Conditions dialog box.
3. Set the boundary conditions for the lens:
Setup → Boundary Conditions → Wall → enclosure-lens
Tab
Setting
Edit...
Value
Thermal
Material name
glass
Radiation
BC Type
semi-transparent
Diffuse Fraction
0
Click Apply and close the Wall dialog box.
4. Copy the boundary conditions for enclosure-lens to other lens boundary.
Setup → Boundary Conditions → Wall → enclosure-lens
Copy...
a. Ensure enclosure-lens is selected in the From Boundary Zone list.
b. Select enclosure-lens-shadow in the To Boundary Zones list.
c. Click Copy.
d. Click OK when prompted to confirm.
e. Close the Copy Conditions dialog box.
5. Set the boundary conditions for the rim bezel:
Setup → Boundary Conditions → Wall → enclosure-rim-bezel
Tab
Setting
Edit...
Value
Thermal
Material name
plastic
Radiation
BC Type
opaque
Internal Emissivity
0.16
Diffuse Fraction
0.1
Click Apply and close the Wall dialog box.
6. Copy the boundary conditions for enclosure-rim-bezel to other rim bezel boundaries.
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Setup → Boundary Zone Conditions → Wall → enclosure-rim-bezel
Copy...
a. Ensure enclosure-rim-bezel is selected in the From Boundary Zone list.
b. Select enclosure-rim-bezel-shadow, holder-rim-bezel, holder-rim-bezel-shadow, housingrim-bezel, and housing-rim-bezel-shadow in the To Boundary Zones list.
c. Click Copy.
d. Click OK when prompted to confirm.
e. Close the Copy Conditions dialog box.
7. Set the boundary conditions for the outer walls
Setup → Boundary Conditions → Wall → enclosure:1
Edit...
a. Click the Thermal tab and select Temperature from the Thermal Conditions list.
b. Enter 298.15 K for Temperature.
c. Click Apply and close the Wall dialog box.
8. Set the boundary conditions for the radiation input surfaces:
Setup → Boundary Conditions → Wall → rad-input
Tab
Edit...
Setting
Thermal
Radiation
Value
Thermal Conditions
Temperature
Temperature
298.15 k
Boundary Source
(enabled)
Direct Irradiation
1200 w/m2
Beam Direction X
-0.848
Beam Direction Y
0
Beam Direction Z
-0.53
Click Apply and close the Wall dialog box.
14.4.8. Solution
1. Specify the discretization schemes..
Solution → Solution → Methods...
Retain the default settiings.
2. Set the convergence criteria for you simulation.
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Setup and Solution
Solution → Reports → Residuals...
a. Ensure that Plot is enabled in the Options group box.
b. Enable Show Advanced Options and select none from the Convergence Criterion dropdown list so that automatic convergence checking does not occur.
c. Click OK to close the Residual Monitors dialog box.
3. Create a surface report definition for max temperature on the inner bezel.
Solution → Reports → Definitions → New → Surface Report → Facet Maximum
a. Enter max-temp for the Name of the surface report definition.
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b. In the Create group box, enable Report Plot and Print to Console.
Note:
Unlike residual values, data from other reports is not saved as part of the solution
set when the ANSYS Fluent data file is saved. If you want to access the surface report
data in future ANSYS Fluent sessions, you can enable the Report File option. The
report file will be saved in your working directory.
c. Select Temperature... and Static Temperature from the Field Variable drop-down lists.
d. Select enclosure-inner_bezel from the Surfaces selection list.
e. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
4. Save the case file (headlamp.cas.h5).
File → Write → Case...
5. Start the calculation.
Solution → Run Calculation → Run Calculation...
a. Enter 99 for Number of Iterations.
b. Click Calculate.
c. Click Yes to initialize the case before solving.
You can monitor the progression of the residuals and the temperature report of the inner bezel during
the run. The residuals spike every 20 iterations when the Monte Carlo model is called and the radiation
quantities are updated. This case is run for a relatively small number of iterations for demonstration
purposes but the temperature on the inner bezel could be monitored for many more iterations until it
reaches a relative steady state.
6. Save the case and data files (headlamp.cas.h5 and headlamp.dat.h5).
File → Write → Case & Data...
14.4.9. Postprocessing
1. Create a contour of temperature on the inner bezel.
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-temp for Contour Name.
b. Ensure the Filled option is enabled in the Options group box.
c. Select Banded in the Coloring group box.
d. Select Temperature... and Static Temperature from the Contours of drop-down lists.
e. Select enclosure-inner-bezel from the Surfaces selection list.
f.
Click Save/Display.
There is a clear hotspot on the inner bezel. You can use the draw mesh function to look at the
location of the hotpsot in relation to the lens.
g. Enable the Draw Mesh option in the Options group box to open the Mesh Display dialog
box.
i.
Deselect all surfaces, then select enclosure-lens from the Surfaces list.
ii. Close the Mesh Display dialog box.
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h. Click Save/Display.
Note:
On highly angular geometries, such as the inner bezel, the Gouraud lighting
method (used by default with the Automatic lighting method) will round off
corners. You may want to consider changing the lighting method to Flat in
the View tab to obtain the view as shown below.
Figure 14.4: Contour of Temperature on Inner Bezel
2. Create a contour of the normalized standard deviation of radiation intensity.
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-rad-std for Contour Name.
b. Ensure the Filled option is enabled in the Options group box.
c. Select Radiation... and Radiation Intensity.Normalized Std Deviation from the Contours
of drop-down lists.
d. Select all surfaces, then deselect enclosure:1 and rad-input from the Surfaces selection list.
e. Click Save/Display and close the Contours dialog box.
The standard deviation is generally less than 30, but still exceeds this value in many small areas,
which is undesirable. Increasing the number of histories in the Monte Carlo radiation model would
lower the standard deviation and improve the results, at the cost of the simulation being more
computationally expensive.
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Figure 14.5: Contour of Radiation Intensity Normalized Standard Deviation on Inner Bezel
3. Save the case file (headlamp.cas.h5).
File → Write → Case...
14.5. Summary
In this tutorial you completed a conduction and radiation simulation to investigate the occurrence of
any hot spots generated by the focusing of rays by the headlamp lens. The MC radiation model is appropriate for modeling collimated beam type radiation where the discretization methods used in the
DO model might be computationally expensive.
You can watch a video of this case being set up, solved, and postprocessed at:
14.6. Further Improvements
This tutorial guides you through the steps to reach a basic solution. You may be able to obtain a more
accurate solution by refining the MC model settings (increasing the number of histories) or running the
case for more iterations. You can also try importing the temperature field into ANSYS Mechanical for a
thermal stress analysis.
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Chapter 15: Using the Eddy Dissipation and Steady
Diffusion Flamelet Combustion Models
This tutorial is divided into the following sections:
15.1. Introduction
15.2. Prerequisites
15.3. Problem Description
15.4. Setup and Solution
15.5. Steady Diffusion Flamelet Model Setup and Solution
15.6. Summary
15.1. Introduction
This tutorial examines the reacting flow through a can combustor that burns methane in air in order
to determine the combustor performance. In this tutorial, you will first mesh the geometry in the ANSYS
Fluent Meshing and then simulate the combustion process using the Eddy Dissipation model. You will
then repeat the simulation using the steady flamelet model and compare the results of these two approaches.
This tutorial demonstrates how to do the following:
• Mesh the geometry in ANSYS Fluent Meshing.
• Set up a combustion simulation in ANSYS Fluent.
• Set up a reacting flow involving fuel and oxidizer.
• Use the Eddy Dissipation model.
• Use the Steady Diffusion Flamelet model.
• Display the results obtained using these two models.
15.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
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15.3. Problem Description
A can type combustor is a component of a land-based gas turbine in which combustion occurs. Can
combustors are designed to burn the fuel efficiently, minimize the emissions, and reduce the wall
temperature. The can combustor to be considered in this tutorial is shown schematically in Figure 15.1: Can Combustor Geometry (p. 594).
Figure 15.1: Can Combustor Geometry
Compressed primary air is forced into the combustion chamber at 10 m/s through the main inlet at the
base of the canister. Six swirl inlet vanes guide the incoming air into the canister and facilitate its mixing
with pure methane for proper combustion. Methane is injected through six fuel inlets with a velocity
of 40 m/s. As the reacting mixture proceeds through the canister, secondary air is fed into the combustion
chamber at a velocity of 6 m/s through six secondary air inlets downstream from the primary combustion
zone. This helps increase the combustion efficiency and also cool the can walls as they are exposed to
the hot reacting flow. The fuel and oxidizer enter the combustion chamber at 300 K.
In this tutorial, the quantitative analysis of the combusting mixture is performed and the following
quantities are determined:
• The expected loss of total pressure through the combustor
• The temperature distribution inside the combustor that burns methane in air
• The proportion of unburned fuel remaining at the combustor outlet
15.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
15.4.1. Preparation
15.4.2. Meshing Workflow
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Setup and Solution
15.4.3. Solver Settings
15.4.4. Models
15.4.5. Boundary Conditions
15.4.6. Solution
15.4.7. Postprocessing for the Eddy-Dissipation Solution
You can also watch a video that demonstrates how to setup, solve, and postprocess the solution results
for diffusion-controlled combustion at:
15.4.1. Preparation
To prepare for running this tutorial:
1.
Download the edm_flamelet.zip file here.
2.
Unzip edm_flamelet.zip to your working directory.
The file can_combustor.pmdb can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Meshing in the top-left selection list to start Fluent in Meshing Mode.
5.
Enable Double Precision under Options.
6.
Set Meshing Processes and Solver Processes to 4 under Parallel (Local Machine).
15.4.2. Meshing Workflow
1. In the Workflow tab on the left of the interface, click the drop-down list and select Watertight
Geometry.
2. Import the CAD geometry (can_combustor.pmdb).
a. Select the Import Geometry task.
b. Enable Advanced Options to expose additional options that may be required when importing
a CAD geometry.
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Select region for the Separate Zone By.
Enter 0.1 for the Tolerance.
Locate the can_combustor.pmdb file using the File Name option and select the file.
c. Select Import Geometry.
3. Add local sizing.
a. Select yes to add local face sizing to the inlets.
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Setup and Solution
i.
Select Face Size for the Size Control Type.
ii. Change the Target Mesh Size to 1.
iii. Select fuelinlet, inletair1 and inletair2 from the list of labels.
iv. Click Add Local Sizing.
b. Add fuelinlet proximity sizing.
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i.
Change the Size Control Type to Proximity.
ii. Adjust the Local Min Size to be 0.5 and the Max Size to be 2.
iii. Change the number of Cells Per Gap to be 16.
iv. Select fuelinlet from the list of labels and click Add Local Sizing.
c. Add proximity sizing to the inlet vanes.
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Setup and Solution
i.
Ensure Proximity is selected and change the Local Min Size to 0.5 and the Max Size to
2.
ii. Change the Select By option to zone.
iii. Select origin-solid:18, origin-solid:20, origin-solid:21, origin-solid:24 and origin-solid:25 from the list of zones.
iv. Click Add Local Sizing.
d. Add face sizing to the inlet vanes.
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i.
Change the Size Control Type to Face Size and enter 1 for the Target Mesh Size.
ii. Select origin-solid:18, origin-solid:20, origin-solid:21, origin-solid:24 and geom-solid:25 from the list of zones.
iii. Click Add Local Sizing.
4. Generate the surface mesh.
a. Adjust the Minimum Size to be 1 and the Maximum Size to be 15.
b. Change the Cells Per Gap to be 4 and click Generate the Surface Mesh.
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Setup and Solution
5. Describe the geometry.
a. In the Describe Geometry task, select the option "The geometry consists of only fluid regions
with no voids".
b. Check that both remaining options are set to "No".
c. Click Describe Geometry.
6. Update the boundaries.
a. Change the wallvanes boundary type to wall.
b. Click Update Boundaries.
7. Update the regions.
a. Retain default settings and click Update Regions.
8. Add boundary layers.
a. Retain default settings and click Add Boundary Layers.
9. Generate the volume mesh.
a. Change the Max Cell Length to 7.5.
b. Click Generate the Volume Mesh to generate the mesh.
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10. Check the quality of the mesh
a. Select Check from the Mesh drop-down list on the main taskbar.
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Setup and Solution
b. Switch to solution mode by clicking the Switch to Solution button on the Fluent ribbon tab.
15.4.3. Solver Settings
1. Retain the default setting of Pressure-Based in the Solver group box, under Type. Retain the
default selection of Steady from the Time list.
Setup →
General
15.4.4. Models
The fuel (methane) and oxidizer (air) undergo fast combustion (that is, the overall combustion rate
is controlled by turbulent mixing). In this first part of the tutorial, the combustion reaction is considered
to be driven by turbulent diffusion, and it is modeled using the Eddy Dissipation model, which is
suitable for modeling fast combustion.
1. Enable the k-ω SST turbulence model.
Physics → Models → Viscous...
a. Retain the default selections in the Viscous Model dialog box.
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b. Click OK to close the Viscous Model dialog box.
2. Enable chemical species transport and reaction.
Physics → Models → Species...
a. Select Species Transport in the Model list.
b. Select methane-air from the Mixture Material drop-down list.
The Mixture Material list contains the set of chemical mixtures that exist in the ANSYS Fluent
database. When selecting an appropriate mixture for your case, you can review the constituent
species and the reactions of the predefined mixture by clicking View... next to the Mixture Material drop-down list. The chemical species and their physical and thermodynamic properties are
defined by the selection of the mixture material. After enabling the Species Transport model, you
can alter the mixture material selection or modify the mixture material properties using the Create/Edit Materials dialog box.
c. Select Volumetric in the Reactions group box.
d. Select Eddy-Dissipation in the Turbulence-Chemistry Interaction group box.
The Eddy-Dissipation model computes the reaction rate under the assumption that chemical reaction
is fast compared to transport of reactants in the combusting flow. That is, the reaction is controlled
by diffusion.
e. Click OK to close the Species Model dialog box.
A Warning message appears in the console notifying you that ANSYS Fluent automatically enabled
the energy equation required for the Species reaction model.
f.
Click OK to close the Information dialog box.
15.4.5. Boundary Conditions
In this step, you will define the boundary conditions at the inlets and the outlet.
1. Set the boundary condition for the fuel inlet.
Setup → Boundary Conditions → Inlet → fuelinlet
Edit...
In the Velocity Inlet dialog box, configure the following settings.
Tab
Setting
Momentum
Velocity Magnitude
Thermal
Temperature
Species
ch4 (Species Mass Fractions group box)
2. Set the boundary condition for the primary air inlet.
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Value
40 m/s
300 (default)
1
Setup and Solution
Setup → Boundary Conditions → Inlet → inletair1
Edit...
In the Velocity Inlet dialog box, configure the following settings.
Tab
Setting
Value
Momentum
Velocity Magnitude
10 m/s
Thermal
Temperature
Species
o2 (Species Mass Fractions group box)
300 (default)
0.23[a]
a. Dry air is composed of 23% of oxygen and 77% of nitrogen, which is a bulk species in the
mixture. ANSYS Fluent adds an appropriate amount of nitrogen at the boundaries to ensure
that the sum of the mass fractions of the components is equal to unity.
3. Set the boundary condition for the secondary air inlet.
Setup → Boundary Conditions → Inlet → inletair2
Edit...
In the Velocity Inlet dialog box, configure the following settings.
Tab
Setting
Value
Momentum
Velocity Magnitude
6 m/s
Thermal
Temperature
Species
o2 (Species Mass Fractions group box)
300 (default)
0.23
4. Set the boundary condition for the pressure outlet.
Setup → Boundary Conditions → Outlet → outlet
Edit...
In the Pressure Outlet dialog box, configure the following settings.
Tab
Momentum
Setting
Value
Gauge Pressure
0 Pa [a] (default)
Backflow Pressure Specification
Total Pressure[b]
(default)
Average Pressure Specification
(Selected)
a. The gauge pressure of 0 Pa means that the pressure equals the ambient pressure.
b. This setting ensures that if the backflow occurs, only pure nitrogen at 300 K enters the chamber,
which will not affect the combustion reactions.
5. For wall-part-fluid, wallvanes and wallvanes-shadow retain the default stationary no slip adiabatic settings.
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15.4.6. Solution
1. Specify the discretization schemes.
Solution → Solution → Methods...
In the Solution Methods task page, configure the following settings.
Group Box
Setting
Value
Pressure Velocity Coupling
Scheme
Coupled
N/A
Pseudo-Transient
(Default)
N/A
Warped-Face Gradient Correction
(Default)
N/A
High Order Term Relaxation
(Selected)[b]
[a]
a. The warped-face gradient correction is designed to improve gradient accuracy for all gradient
methods.
b. The relaxation of high order terms will help to improve the solution behavior of flow simulations
when higher order spatial discretizations are used (higher than first).
2. Ensure that the plotting of residuals is enabled during the calculation.
Solution → Reports → Residuals...
3. Create a surface report definition of mass-weighted average of co2 at the outlet.
Solution → Reports → Definitions → New → Surface Report → Mass-Weighted Average...
Configure the following settings.
Group Box
Setting
Value
N/A
Name
N/A
Field Variable
N/A
Surfaces
Create
Report File
(Selected)
Report Plot
(Selected)
Print to Console
(Selected)
co2-out
Species... and Mass fraction of co2
outlet
4. Initialize the solution.
Solution → Initialization → Initialize
5. Save the case file (can_combustor_edm.cas.h5).
File → Write → Case...
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Setup and Solution
6. Start calculation.
Solution → Run Calculation → Run Calculation...
a. Set the global Timescale Factor to 5.
The Timescale Factor allows you to further manipulate the computed Time Step calculated by
ANSYS Fluent. Larger time steps can lead to faster convergence. However, if the time step is too
large it can lead to solution instability.
b. Enter 500 for Number of Iterations.
c. Click Calculate.
All scaled residuals have met the criteria for a converged solution (Figure 15.2: Scaled Residuals (p. 607)),
and the relative amount of CO2 exiting the combustor outlet has become stable (Figure 15.3: Convergence
History of Mass-Weighted Average CO2 on the Outlet (p. 608)).
Figure 15.2: Scaled Residuals
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Figure 15.3: Convergence History of Mass-Weighted Average CO2 on the Outlet
7. Save the case and data files (can_combustor_edm.cas.h5 and can_combustor_edm.dat.h5).
File → Write → Case & Data...
15.4.7. Postprocessing for the Eddy-Dissipation Solution
1. Check the mass flux balance.
Results → Reports → Fluxes...
Warning:
Although the mass flow rate history indicates that the solution is converged, you
should also check the net mass fluxes through the domain to ensure that mass is
being conserved.
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Setup and Solution
a. Select fuelinlet, inletair1, inletair2 and outlet from the Boundaries selection list.
b. Retain the default Mass Flow Rate option.
c. Click Compute and close the Flux Reports dialog box.
Warning:
The net mass imbalance should be a small fraction (for example, 0.5%) of the total
flux through the system. If a significant imbalance occurs, you should decrease
the residual tolerances by at least an order of magnitude and continue iterating.
2. Report the total sensible heat flux.
Results → Reports → Fluxes...
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a. Select Total Sensible Heat Transfer Rate in the Options list.
b. Select all the boundaries from the Boundaries selection list (you can click the select-all button
(
).
c. Click Compute and close the Flux Reports dialog box.
Note:
The energy balance is good because the net result is small compared to the heat
of reaction.
3. Create an XZ plane, which will be used for plotting the results.
Results → Surface → Create → Plane...
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Setup and Solution
a. Enter plane_xz in for New Surface Name.
b. In the Method drop-down list, select Point and Normal.
c. In the Point group box, enter 1, 0, 1 for X, Y, Z, respectively.
d. In the Normal group box, enter 0, 1, 0 for iX, iY, iZ, respectively.
e. Click Create and close the Plane Surface dialog box.
4. Display filled contours of CO2 mass fraction in the combustion chamber (Figure 15.4: Contours of
CO2 Mass Fraction (p. 612)).
Results → Graphics → Contours → New...
a. Enter co2-mass-fraction for Contour Name.
b. Enable Filled in the Options group box.
c. From the Contours of drop-down lists, select Species... and Mass Fraction of co2.
d. From the Surfaces selection list, deselect all surfaces and select plane_xz.
e. In the Coloring group box, select Smooth.
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f.
Click Save/Display, close the Contours dialog box, and rotate the view as shown in Figure 15.4: Contours of CO2 Mass Fraction (p. 612).
Figure 15.4: Contours of CO2 Mass Fraction
Note:
You may need to deselect Headlight and then Lighting in the View ribbon tab
(Display group).
The contour map of the CO2 concentration shows that the flow is mixing and reacting properly in
the combustor.
5. Display filled contours of oxygen mass fraction on the surface plane_xz (Figure 15.5: Contours of
O2 Mass Fraction (p. 613)).
Results → Graphics → Contours → New...
a. Enter o2-mass-fraction for Contour Name.
b. Enable Filled in the Options group box.
c. From the Contours of drop-down lists, select Species... and Mass Fraction of o2.
d. From the Surfaces selection list, deselect all surfaces and select plane_xz.
e. In the Coloring group box, select Smooth.
f.
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Click Save/Display and close the Contours dialog box.
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Setup and Solution
Figure 15.5: Contours of O2 Mass Fraction
6. Display filled contours of temperature on the aluminum combustor walls (Figure 15.6: Contours
of Static Temperature on the Combustor Walls (p. 614)).
Results → Graphics → Contours → New...
a. Enter surface-temperature for Contour Name.
b. Enable Filled in the Options group box.
c. From the Contours of drop-down lists, select Temperature... and Static Temperature.
d. Click New Surface and select Iso-Clip.
e. Name the surface clip-y-coordinate and select Mesh... and Y-Coordinate from the
Clip to Values of drop-down lists.
f.
Select the surface solid:1.
g. Click Compute and enter 0 for the Min (m).
h. Click Create and close the dialog box.
i.
From the Surfaces selection list, deselect all surfaces and select clip-y-coordinate and
wallvanes.
j.
In the Coloring group box, select Smooth.
k. Click Save/Display and close the Contours dialog box.
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Figure 15.6: Contours of Static Temperature on the Combustor Walls
l.
Rotate the contour plot to examine the temperature field of the combusting flow on the canister walls from different angles.
7. Save the case and data files (can_combustor_edm.cas.h5 and can_combustor_edm.dat.h5).
File → Write → Case & Data...
15.5. Steady Diffusion Flamelet Model Setup and Solution
In the first part of the tutorial, the combustion reaction was modeled using the Eddy Dissipation model.
In this part of the tutorial, you will use the Steady Diffusion Flamelet model to simulate a turbulent
non-premixed reacting flow. The Steady Diffusion Flamelet model can model local chemical non-equilibrium due to turbulent strain.
In the Steady Diffusion Flamelet model, reactions take place in a thin laminar locally one-dimensional
zone, called 'flamelet'. The turbulent flame is represented by an ensemble of such flamelets. Detailed
chemical kinetics is used to describe the combustion reaction. The chemistry is assumed to respond
rapidly to the turbulent strain, and as the strain relaxes to zero, the chemistry tends to equilibrium.
Despite the tendency toward equilibrium, a flamelet solution can often yield more accurate results than
an Eddy Dissipation or one- or two-step Finite Rate solution. This is because all the chemistry details
are included, making it possible to capture some of the faster intermediate reactions. To model turbulent
mixing, a probability density function (PDF) table is used as a lookup table at run time.
To watch a video that demonstrates some steps shown below, go to
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Steady Diffusion Flamelet Model Setup and Solution
15.5.1. Models
Specify settings for non-premixed combustion.
Physics → Models → Species...
1. In the Model group box, select Non-Premixed Combustion.
2. In the State Relation group box, select Steady Diffusion Flamelet.
3. Retain the selection of Create Flamelet in the Options group box.
If you are generating a flamelet file yourself, you need to read in the chemical kinetics mechanism and
thermodynamic data, which must be in CHEMKIN format.
4. Click Import CHEMKIN Mechanism...
5. In the CHEMKIN Mechanism Import dialog box, in the Kinetics Input File text entry field, enter
the following:
path\KINetics\data\grimech30_50spec_mech.inp
where path is the ANSYS Fluent installation directory (for example, C:\Program Files\ANSYS
Inc\v211\fluent\fluent21.1.0).
6. Click Import.
Once the reacting data file has been imported, the tab for specifying the fuel and oxidizer compositions,
flamelet and PDF table become accessible.
7. In the Boundary tab, specify the fuel (methane) and oxidizer (air) stream compositions in mass
fractions.
a. In the Specify Species in group box, make sure that Mass Fraction is selected.
b. Configure the following settings:
Group
Species
Mass Fraction
Fuel
ch4
1.0
Oxid
o2
0.233 (default)
n2
0.767 (default)
Tip:
Scroll down to see all the species.
Note:
All boundary species with a mass or mole fraction of zero will be ignored.
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c. In the Temperature group box, retain the default values of 300 K for Fuel and Oxid.
8. In the Control tab, retain the default settings.
9. In the Flamelet tab, retain the default settings and click Calculate Flamelets.
Once the diffusion flamelets are generated, a Question dialog box opens, asking whether you want
to save flamelets to a file. Click No.
10. In the Table tab, retain the default settings for the table parameters and click Calculate PDF
Table to compute a non-adiabatic probability density function (PDF) table.
11. Click Display PDF Table...
12. In the PDF Table dialog box, retain the selection of Mean Temperature from the Plot Variable
drop-down list and all the other default parameters and click Display.
In the graphical display of the 3D look-up table, the Z axis represents the mean temperature of the
reacting fluid, and the X and Y axes represent the mean mixture fraction and the scaled variance, respectively.
The maximum and minimum values for mean temperature and the corresponding mean mixture
fraction and scale variance are also reported in the console.
The 3D look-up tables are reviewed on a slice-by-slice basis. By default, the slice selected corresponds
to the adiabatic enthalpy values. You can also select other slices of constant enthalpy for display.
13. Save the PDF output file (can_combustor_flamelet.pdf.gz).
File → Write → PDF...
a. Enter can_combustor_flamelet.pdf.gz for PDF File name.
b. Click OK to write the file.
By default, the file will be saved as formatted (ASCII, or text). To save a binary (unformatted) file,
enable the Write Binary Files option in the Select File dialog box.
14. Click Close to close the PDF Table dialog box.
15. Click OK to close the Species Model dialog box.
15.5.2. Boundary Conditions
Specify the boundary condition for the fuel inlet.
Setup → Boundary Conditions → Inlet → fuelinlet
Edit...
1. In the Velocity Inlet dialog box, under the Species tab, enter 1 for Mean Mixture Fraction.
The value of 1 indicates that only pure methane will be entering the fuelinlet boundary.
2. Click Apply and close the Velocity Inlet dialog box.
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Steady Diffusion Flamelet Model Setup and Solution
15.5.3. Solution
1. Edit the output filename for mass-weighted average of co2 at the outlet.
Solution → Monitors → Report Files → co2-out-rfile
Edit...
a. Enter co2-out-fl-rfile.out for File Name.
b. Click OK to close the Edit Report File dialog box.
2. Save the case file (can_combustor_flamelet.cas.h5).
File → Write → Case...
3. Reinitialize the solution.
Solution → Initialization → Initialize
4. In the Run Calculation task page, retain the settings of 5 for Timescale Factor and 500 for
Number of Iterations and click Calculate.
Solution → Run Calculation → Run Calculation...
5. Save the case and data files (can_combustor_flamelet.cas.h5 and can_combustor_flamelet.dat.h5).
File → Write → Case & Data...
15.5.4. Postprocessing for the Steady Diffusion Flamelet Solution
1. Check the mass flux balance and the total sensible heat flux. Here, it is important for the total
sensible net heat flux to be at least less than 1% of the reaction source.
Note that in this case, the residuals may not converge. It is important to utilize both the flux calculations
along with the monitor plot to determine whether the solution has converged.
2. Display filled contours of mean mixture fraction on the surface plane_xz (Figure 15.7: Contours
of Mean Mixture Fraction (p. 618)).
Results → Graphics → Contours → New...
a. Enter mean-mixture-fraction for Contour Name.
b. From the Contours of drop-down lists, select Pdf... and Mean Mixture Fraction.
c. From the Surfaces selection list, deselect all surfaces and select plane_xz.
d. Enable Filled in the Options group box.
e. Clear the Auto Range and Clip to Range options.
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f.
Enter 0.15 for Max.
g. In the Coloring group box, select Smooth.
h. Click Save/Display.
Figure 15.7: Contours of Mean Mixture Fraction
3. Display filled contours of CO2 mass fraction in the combustion chamber (Figure 15.8: Contours of
CO2 Mass Fraction (p. 619)).
Results → Graphics → Contours → co2-mass-fraction
618
Display
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Steady Diffusion Flamelet Model Setup and Solution
Figure 15.8: Contours of CO2 Mass Fraction
The steady diffusion flamelet simulation yields a significantly different CO2 mass fraction distribution
as compared to the eddy dissipation model calculation. The lower CO2 concentration at the base of
the flamelet flame is caused by low local temperature in the area, which results in slower combustion.
In the eddy dissipation model, chemical kinetics is ignored, and the reaction is controlled by turbulent
mixing of the materials. In this case, the CO2 concentration is greater near the base of the flame because
the rate of mixing is high in the area (see Figure 15.4: Contours of CO2 Mass Fraction (p. 612)).
4. Display the outlet CO2 concentration profiles for both solutions on a single plot.
Results → Plots → Data Sources...
a. In the Plot Data Sources dialog box, click the Load File... button to open the Select File
dialog box.
b. In the Select File dialog box that opens, click once on co2-out-fl-rfile.out and co2-outrfile.out.
Each of these files will be listed with their folder path in the bottom list to indicate that they have
been selected.
Tip:
If you select a file by mistake, simply click the file in the bottom list and then
click Remove.
c. Click OK to save the files and close the Select File dialog box.
d. In the Plot group box, enter co2-out for Title.
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e. From the Curve Information selection list, select co2-out-rfile.out | Iteration | co2-out
f.
Enter co2-EDM in the lower-right text-entry box under the Legend Names selection list.
g. Click the Change Legend Entry button.
The item in the Legend Entries list for co2-out-rfile.out | Iteration | co2-out will be changed to
co2-EDM. This legend entry will be displayed in the upper-left corner of the XY plot generated in
a later step.
h. In a similar manner, change the legend entry for the co2-out-fl-rfile.out | Iteration | co2-out
curve to be co2-Flamelet.
i.
Click the Axes... button to open the Axes dialog box.
i.
From the Axis list, select Y.
ii. Enter 2 for Precision.
iii. Click Apply and close the Axes dialog box.
j.
Click the Curves... button to open the Curves dialog box, where you will define a different
curve symbol for the CO2 concentration data.
i.
Retain 0 for the Curve #.
ii. Select ---- from the Pattern drop-down list.
iii. From the Symbol drop-down list, select the "blank" choice, which is the first item in the
Symbol list.
iv. Click Apply.
v. Set Curve # to 1 by clicking the up-arrow button.
vi. Modify the settings for Pattern and Symbol in a manner similar to that for the previous
curve.
vii. Click Apply and close the Curves dialog box.
k. Click Plot and close the Plot Data Sources dialog box.
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Summary
Figure 15.9: Convergence History of Mass-Weighted Average CO2 on the Outlet
Despite the model differences, both models predicted similar mass-weighted average mass fractions
of CO2 exiting the combustor during the steady-state. However, the steady diffusion flamelet
model predicts less CO2 exiting the combustor and, due to its more realistic description of combustion
kinetics, is considered to be more accurate.
5. Save the case file (can_combustor_flamelet.cas.h5).
File → Write → Case...
You can perform further postprocessing of the solution results as shown in the following video:
15.6. Summary
In this tutorial, you have learned how to model the reacting flow through a can combustor using the
eddy dissipation model and steady diffusion flamelet model in ANSYS Fluent.
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Chapter 16: Modeling Surface Chemistry
This tutorial is divided into the following sections:
16.1. Introduction
16.2. Prerequisites
16.3. Problem Description
16.4. Setup and Solution
16.5. Summary
16.1. Introduction
In chemically reacting laminar flows, such as those encountered in chemical vapor deposition (CVD)
applications, accurate modeling of time-dependent hydrodynamics, heat and mass transfer, and
chemical reactions (including wall surface reactions) is important.
In this tutorial, surface reactions are considered. Modeling the reactions taking place at gas-solid interfaces
is complex and involves several elementary physicochemical processes like adsorption of gas-phase
species on the surface, chemical reactions occurring on the surface, and desorption of gases from the
surface back to the gas phase.
This tutorial demonstrates how to do the following:
• Create new materials and set the mixture properties.
• Model surface reactions involving site species.
• Enable physical models and define boundary conditions for a chemically reacting laminar flow involving
wall surface reactions.
• Calculate the deposition solution using the pressure-based solver.
• Examine the flow results using graphics.
16.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
Before beginning with this tutorial, see the Fluent User's Guide for more information about species
transport, chemically reacting flows, wall surface reaction modeling, and chemical vapor deposition. In
particular, you should be familiar with the Arrhenius rate equation, as this equation is used for the
surface reactions modeled in this tutorial.
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16.3. Problem Description
A rotating disk CVD reactor for the growth of Gallium Arsenide (GaAs) shown in Figure 16.1: Schematic
of the Reactor Configuration (p. 624) will be modeled.
Figure 16.1: Schematic of the Reactor Configuration
The process gases, Trimethyl Gallium (
) and Arsine (
) enter the reactor at 293 K through
the inlet at the top. These gases flow over the hot, spinning disk depositing thin layers of gallium and
arsenide on it in a uniform, repeatable manner. The disk rotation generates a radially pumping effect,
which forces the gases to flow in a laminar manner down to the growth surface, outward across the
disk, and finally to be discharged from the reactor.
The semiconductor materials Ga(s) and As(s) are deposited on the heated surface governed by the following surface reactions.
(16.1)
(16.2)
The inlet gas is a mixture of Trimethyl Gallium, which has a mass fraction of 0.15, and Arsine, which has
a mass fraction of 0.4, the remainder is hydrogen. The mixture velocity at the inlet is 0.02189 m/s. The
disk rotates at 80 rad/sec. The top wall (wall-1) is heated to 473 K and the sidewalls (wall-2) of the reactor
are maintained at 343 K. The susceptor (wall-4) is heated to a uniform temperature of 1023 K and the
bottom wall (wall-6) is at 303 K. These CVD reactors are typically known as cold-wall reactors, where
only the wafer surface is heated to higher temperatures, while the remaining reactor walls are maintained
at low temperatures.
In this tutorial, simultaneous deposition of Ga and As is simulated and examined. The mixture properties
and the mass diffusivity are determined based on kinetic theory. Detailed surface reactions with multiple
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sites and site species, and full multi-component/thermal diffusion effects are also included in the simulation.
The purpose of this tutorial is to demonstrate surface reaction capabilities in ANSYS Fluent. Convective
heat transfer is considered to be the dominant mechanism compared to radiative heat transfer, thus
radiation effects are ignored.
16.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
16.4.1. Preparation
16.4.2. Reading and Checking the Mesh
16.4.3. Solver and Analysis Type
16.4.4. Specifying the Models
16.4.5. Defining Materials and Properties
16.4.6. Specifying Boundary Conditions
16.4.7. Setting the Operating Conditions
16.4.8. Simulating Non-Reacting Flow
16.4.9. Simulating Reacting Flow
16.4.10. Postprocessing the Solution Results
16.4.1. Preparation
To prepare for running this tutorial:
1.
Download the surface_chem.zip file here.
2.
Unzip surface_chem.zip to your working directory.
The mesh file surface.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
16.4.2. Reading and Checking the Mesh
1. Read the mesh file surface.msh.
File → Read → Mesh...
2. Check the mesh.
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Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and will report the progress in the console. Ensure
that the reported minimum volume is a positive number.
3. Scale the mesh.
Domain → Mesh → Scale...
Scale the mesh to meters as it was created in centimeters.
a. Select cm (centimeters) from the Mesh Was Created In drop-down list in the Scaling group
box.
b. Click Scale and verify that the domain extents are as shown in the Scale Mesh dialog box.
The default SI units will be used in this tutorial, hence there is no need to change any units.
c. Close the Scale Mesh dialog box.
d. Re-display the mesh
e. Click the Fit to Window icon,
.
4. Check the mesh.
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Domain → Mesh → Check → Perform Mesh Check
Note:
It is a good practice to check the mesh after manipulating it (scale, convert to polyhedra,
merge, separate, fuse, add zones, or smooth and swap). This will ensure that the quality
of the mesh has not been compromised.
5. Examine the mesh (Figure 16.2: Mesh Display (p. 627)).
Figure 16.2: Mesh Display
Extra:
You can use the left mouse button to rotate the image and view it from different angles.
Use the right mouse button to check which zone number corresponds to each
boundary. If you click the right mouse button on one of the boundaries in the graphics
window, its name and type will be printed in the ANSYS Fluent console. This feature
is especially useful when you have several zones of the same type and you want to
distinguish between them quickly. Use the middle mouse button to zoom the image.
16.4.3. Solver and Analysis Type
Retain the default setting of Pressure-Based in the Solver group box, under Type. Retain the default
selection of Steady from the Time list.
Physics → Solver → General
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16.4.4. Specifying the Models
In this problem, the energy equation and the species conservation equations will be solved, along with
the momentum and continuity equations.
1. Enable heat transfer by turning on the energy equation.
Physics → Models → Energy
2. Enable the laminar viscous model.
Physics → Models → Viscous...
a. Select Laminar in the Model group box.
b. Click OK to close the Viscous Model dialog box.
3. Enable chemical species transport.
Physics → Models → Species...
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a. Select Species Transport in the Model list.
The Species Model dialog box will expand to show relevant input options.
b. Retain the selection of mixture-template from the Mixture Material drop-down list.
You will modify the mixture material later in this tutorial.
c. Retain the default setting for Diffusion Energy Source.
This includes the effect of enthalpy transport due to species diffusion in the energy equation, which
contributes to the energy balance, especially for the case of Lewis numbers far from unity.
d. Enable Full Multicomponent Diffusion and Thermal Diffusion.
The Full Multicomponent Diffusion activates Stefan-Maxwell’s equations and computes the diffusive fluxes of all species in the mixture to all concentration gradients. The Thermal Diffusion
effects cause heavy molecules to diffuse less rapidly, and light molecules to diffuse more rapidly,
toward heated surfaces.
e. Click Apply.
f.
Click OK to close the Species Model dialog box.
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16.4.5. Defining Materials and Properties
In the following steps you will copy the gas-phase species (AsH3 , Ga(CH3)3 , CH3 , and H2 ) from the ANSYS
Fluent database, specify the mixture materials, setup the reactions, and modify the material properties.
You will also create the site species (Ga_s and As_s) and the solid species (Ga and As).
1. Copy arsenic-trihydride, hydrogen, methyl-radical, and trimethyl-gallium from the ANSYS Fluent
material database to the list of fluid materials and modify their properties.
Setup → Materials → Fluid → air
Edit...
a. Click Fluent Database... in the Create/Edit Materials dialog box to open the Fluent Database
Materials dialog box.
b. In the Fluent Database Materials dialog box, select fluid from the Material Type drop-down
list.
c. From the Fluent Fluid Materials selection list, select arsenic-trihydride (ash3), hydrogen
(h2), methyl-radical (ch3), and trimethyl-gallium (game3) by clicking each species once.
Scroll down the Fluent Fluid Materials list to locate each species.
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d. Click Copy to copy the selected species to your model.
e. Click Close to close the Fluent Database Materials dialog box.
2. Create the site species (Ga_s and As_s) and the solid species (Ga and As).
a. In the Create/Edit Materials dialog box, select air from the Fluent Fluid Materials drop-down
list.
b. Enter ga_s for the Name text entry field.
c. Enter ga_s for the Chemical Formula text entry field.
d. Click Change/Create to create the new material.
e. Click No in the Question dialog box when asked if you want to overwrite air.
The new material ga_s is added to your model and listed under Fluid in the Materials task
page and under the Setup/Materials/Fluid tree branch.
f.
Create as_s, ga and as following the same procedure as for ga_s and close the Create/Edit
Materials dialog box.
Extra:
To enter complex formulae such as Ga(CH3)3 in the text entry box, use ‘<’ and ‘>’ instead
of ‘(’ and ‘ )’, respectively.
3. Set the mixture species.
Setup → Materials → Mixture → mixture-template
Edit...
a. Enter gaas_deposition for Name.
b. Click Change/Create.
c. Click Yes in the Question dialog box to overwrite the mixture-template.
d. Set the Selected Species.
i.
In Properties group box, click the Edit... button to the right of the names drop-down list
for Mixture Species to open the Species dialog box.
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ii. Set the Selected Species from the Available Materials selection list as shown in
Table 16.1: Selected Species (p. 632) .
Table 16.1: Selected Species
Selected Species
ash3
game3
ch3
h2
Important:
• Add arsenic-trihydride (ash3), trimethyl-gallium (game3), methyl-radical
(ch3), and hydrogen (h2) to the Selected Species list before removing h2o,
o2, and n2.
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• Ensure that h2 is at the bottom in the Selected Species selection list as shown
in Table 16.1: Selected Species (p. 632). ANSYS Fluent will interpret the last
species in the list as the bulk species.
Note:
To add/remove the species:
• To add a particular species to the list, select the required species from the
Available Materials selection list and click Add in the corresponding species
selection list (Selected Species, Selected Site Species, or Selected Solid
Species). The species will be added to the end of the relevant list and removed
from the Available Materials list.
• To remove an unwanted species from the selection list, select the species
from the selection list (Selected Species, Selected Site Species, or Selected
Solid Species) and click Remove in the corresponding selection list. The
species will be removed from the list and added to the Available Materials
list.
iii. Click OK to close the Species dialog box.
iv. Click Change/Create and close the Creat/Edit Materials dialog box.
4. Enable chemical species transport reaction.
Physics → Models → Species...
Although you enable reactions, you still run a non-reacting flow to produce an initial solution. You
will run a reacting flow in Simulating Reacting Flow (p. 651).
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a. Enable Volumetric and Wall Surface in the Reactions group box.
b. Retain the selection of gaas_deposition from the Mixture Material drop-down list.
c. Disable Heat of Surface Reactions and enable Mass Deposition Source.
d. Click OK to close the Species Model dialog box.
5. Set the site and solid species and the mixture reactions in a similar manner to the mixture species.
Setup → Materials → Mixture → gaas_deposition
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Setup and Solution
a. Click the Edit... button to the right of the names drop-down list for Mixture Species in the
Properties group box.
Specify the Selected Site Species and the Selected Solid Species as shown in
Table 16.2: Selected Site and Solid Species (p. 635).
Table 16.2: Selected Site and Solid Species
Selected Site Species
Selected Solid Species
ga_s
ga
as_s
as
Once you set the site and solid species, the Species dialog box should look like this:
b. Click OK to close the Species dialog box.
c. Click the Edit... button to the right of the Reaction drop-down list to open the Reactions
dialog box.
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d. Increase the Total Number of Reactions to 2, and define the following reactions using the
parameters in Table 16.3: Reaction Parameters (p. 636) :
(16.3)
(16.4)
Table 16.3: Reaction Parameters
Parameter
636
For Equation 16.3 (p. 636)
For Equation 16.4 (p. 636)
Reaction ID
1
2
Reaction Name
gallium-dep
arsenic-dep
Reaction Type
Wall Surface
Wall Surface
Number of Reactants
2
2
Species
ash3, ga_s
game3, as_s
a
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Parameter
For Equation 16.3 (p. 636)
For Equation 16.4 (p. 636)
Stoich. Coefficient
ash3= 1, ga_s= 1
game3= 1, as_s= 1
Rate Exponent
ash3= 1, ga_s= 1
game3= 1, as_s= 1
Arrhenius Rate
PEF= 1e+06, AE= 0, TE= 0.5
Number of Products
3
3
Species
ga, as_s, h2
as, ga_s, ch3
Stoich. Coefficient
ga= 1, as_s= 1, h2= 1.5
as= 1, ga_s= 1, ch3= 3
Rate Exponent
as_s= 0, h2= 0
ga_s= 0, ch3= 0
b
PEF= 1e+12, AE= 0, TE= 0.5
Set the ID to 2 in order to set the parameters for the second reaction.
Here, PEF = Pre-Exponential Factor, AE = Activation Energy, and TE = Temperature Exponent.
e. Click OK to save the data and close the Reactions dialog box.
f.
Set the reaction mechanisms for the mixture.
i.
Click the Edit... button to the right of the Mechanism drop-down list to open the Reaction
Mechanisms dialog box.
ii. Retain Number of Mechanisms as 1.
iii. Enter gaas-ald for Name.
iv. Select Wall Surface in the Reaction Type group box.
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v. Select gallium-dep and arsenic-dep from the Reactions selection list.
vi. Set Number of Sites to 1.
vii. Enter 1e-08 kgmol/m2 for Site Density for site-1.
viii.Click the Define... button to the right of site-1 to open the Site Parameters dialog box.
A. Set Total Number of Site Species to 2.
B. Select ga_s as the first site species and enter 0.7 for Initial Site Coverage.
C. Select as_s as the second site species and enter 0.3 for Initial Site Coverage.
D. Click Apply and close the Site Parameters dialog box.
ix. Click OK to close the Reaction Mechanisms dialog box.
g. Retain the default selection of incompressible-ideal-gas from the Density drop-down list.
h. Retain the default selection of mixing-law from the Cp (Specific Heat) drop-down list.
i.
Select mass-weighted-mixing-law from the Thermal Conductivity drop-down list.
j.
Select mass-weighted-mixing-law from the Viscosity drop-down list.
k. Retain the default selection of kinetic-theory from the Mass Diffusivity drop-down list.
l.
Retain the default selection of kinetic-theory from the Thermal Diffusion Coefficient dropdown list.
m. Click Change/Create and close the Create/Edit Materials dialog box.
6. Specify the material properties for arsenic-trihydride, hydrogen, methyl-radical, trimethyl-gallium,
site species (Ga_s and As_s), and solid species (Ga and As).
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Setup → Materials → Mixture → gaas_deposition → arsenic-trihydride
Edit...
a. In the Properties group box, modify the arsenic-trihydride properties as shown in
Table 16.4: Properties of Species (p. 639).
Important:
Ensure Mixture is set to gaas_deposition
Tip:
Scroll down in the Properties group box to see all the parameters.
Table 16.4: Properties of Species
Parameter
AsH_3
Ga(CH_3)_3
CH_3
H_2
Name
arsenictrihydride
trimethylgallium
methyl-radical
hydrogen
Chemical Formula
ash3
game3
ch3
h2
Cp (Specific Heat)
piecewisepolynomial
piecewisepolynomial
piecewise-polynomial
piecewise-polynomial
kinetic-theory
kinetic-theory
kinetic-theory
Thermal Conductiv- kinetic-theory
ity
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Parameter
AsH_3
Ga(CH_3)_3
CH_3
H_2
Viscosity
kinetic-theory
kinetic-theory
kinetic-theory
kinetic-theory
Molecular Weight
77.95
114.83
15
2.02
Standard State Enthalpy
0
0
2.044e+07
0
Standard State Entropy
130579.1
130579.1
257367.6
130579.1
Reference Temperature
298.15
298.15
298.15
298.15
L-J Characteristic
Length
4.145
5.68
3.758
2.827
398
148.6
59.7
L-J Energy Paramet- 259.8
er
b. When finished, click Change/Create to update your local copy of the species material.
Note:
When you modify the properties of the material local copy, the original copy in
Fluent material database stays intact.
c. In a similar way, modify the properties of trimethyl-gallium (game3), methyl-radical (ch3),
and hydrogen (h2).
Note:
Make sure to click Change/Create each time you modify the properties for the
material to apply the changes to the local copy.
d. Select ga_s from the Fluent Fluid Materials drop-down list.
e. Enter the parameter values for the ga_s species as shown in Table 16.5: Properties of Species (p. 640).
Table 16.5: Properties of Species
Parameter
640
Ga_s
As_s
Ga
As
Name
ga_s
as_s
ga
as
Chemical Formula
ga_s
as_s
ga
as
Cp (Specific Heat)
520.64
520.64
1006.43
1006.43
Thermal Conductivity
0.0158
0.0158
kinetic-theory
kinetic-theory
Viscosity
2.125e-05
2.125e-05
kinetic-theory
kinetic-theory
Molecular Weight
69.72
74.92
69.72
74.92
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Setup and Solution
Parameter
f.
Ga_s
As_s
Ga
As
Standard State
Enthalpy
-3117.71
-3117.71
0
0
Standard State
Entropy
154719.3
154719.3
0
0
Reference Temper- 298.15
ature
298.15
298.15
298.15
L-J Characteristic
Length
0
0
0
0
L-J Energy Parameter
0
0
0
0
Modify the material properties for As_s, Ga, and As as shown in Table 16.5: Properties of Species (p. 640).
g. Close the Create/Edit Materials dialog box.
16.4.6. Specifying Boundary Conditions
1. Set the conditions for velocity-inlet.
Setup → Boundary Conditions → Inlet → velocity-inlet
Edit...
a. Retain the default selection of Magnitude, Normal to Boundary from the Velocity Specification Method drop-down list.
b. Retain the default selection of Absolute from the Reference Frame drop-down list.
c. Enter 0.02189 m/s for Velocity Magnitude.
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d. Click the Thermal tab and enter 293 K for Temperature.
e. Under the Species tab, set the Species Mass Fractions for ash3 to 0.4, game3 to 0.15, and
ch3 to 0.
The mass fraction of hydrogen is 0.45, but there is no need to specify this since it is the last species
in the mixture.
f.
Click Apply and close the Velocity Inlet dialog box.
2. Set the boundary conditions for outlet.
Setup → Boundary Conditions → Outlet → outlet
Edit...
a. Retain the default settings under the Momentum tab.
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b. Under the Thermal tab, enter 400 K for Temperature.
c. Under the Species tab, set the Backflow Species Mass Fractions for ash3 to 0.32, game3
to 0.018, and ch3 to 0.06.
Since a certain amount of backflow is expected in the flow regions around the rotating shaft,
you should set the realistic backflow species mass fractions to minimize convergence difficulties.
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d. Click Apply and close the Pressure Oulet dialog box.
3. Set the boundary conditions for wall-1.
Setup → Boundary Conditions → Wall → wall-1
Edit...
a. Click the Thermal tab.
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i.
Select Temperature in the Thermal Conditions group box.
ii. Enter 473 K for Temperature.
b. Click Apply and close the Wall dialog box.
4. Set the boundary conditions for wall-2.
Setup → Boundary Conditions → Wall → wall-2
Edit...
a. Click the Thermal tab.
i.
Select Temperature in the Thermal Conditions group box.
ii. Enter 343 K for Temperature.
b. Click Apply and close the Wall dialog box.
5. Set the boundary conditions for wall-4.
Setup → Boundary Conditions → Wall → wall-4
Edit...
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a. Select Moving Wall in the Wall Motion group box.
The Wall dialog box will expand to wall motion inputs and options.
b. Select Absolute and Rotational in the Motion group box.
c. Enter 80 rad/s for Speed.
d. Retain the other default settings.
e. Click the Thermal tab.
i.
Select Temperature in the Thermal Conditions group box.
ii. Enter 1023 K for Temperature.
f.
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Click the Species tab.
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i.
Enable Reaction.
ii. Retain the selection of gaas-ald from the Reaction Mechanisms drop-down list.
g. Click Apply and close the Wall dialog box.
6. Set the boundary conditions for wall-5.
Setup → Boundary Conditions → Wall → wall-5
Edit...
a. Select Moving Wall in the Wall Motion group box.
b. Select Absolute and Rotational in the Motion group box.
c. Enter 80 rad/s for Speed.
d. Click the Thermal tab.
i.
Select Temperature in the Thermal Conditions group box.
ii. Enter 720 K for Temperature.
e. Click Apply and close the Wall dialog box.
7. Set the boundary conditions for wall-6.
Setup → Boundary Conditions → Wall → wall-6
Edit...
a. Click the Thermal tab.
i.
Select Temperature in the Thermal Conditions group box.
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ii. Enter 303 K for Temperature.
b. Click Apply and close the Wall dialog box.
16.4.7. Setting the Operating Conditions
1.
Physics → Solver → Operating Conditions...
a. Enter 10000 Pa for Operating Pressure.
b. Enable Gravity.
The dialog box will expand to show related gravitational inputs.
c. Enter 9.81 m/s2 for Gravitational Acceleration in the Z direction.
d. Enter 303 K for Operating Temperature.
e. Click OK to close the Operating Conditions dialog box.
The Operating Conditions dialog box can be accessed from the Cell Zone Conditions task page.
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Setup and Solution
16.4.8. Simulating Non-Reacting Flow
1. Disable Volumetric for solving non-reacting flow.
Physics → Models → Species...
a. Disable Volumetric in the Reactions group box.
b. Click OK to close the Species Model dialog box.
You will first run a non-reacting solution to establish the flow.
2. Select the Coupled solver method.
Solution →
Solution Methods
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Retain the default selections.
3. Enable residual plotting during the calculation.
Solution → Reports → Residuals...
a. Retain the default settings and close the Residual Monitors dialog box.
4. Initialize the flow field.
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Solution →
Initialization
a. Retain the default selection of Hybrid Initialization from the Initialization Methods group
box.
b. Click Initialize.
5. Save the case file (surface-non-react.cas.h5).
File → Write → Case...
6. Start the calculation by requesting 200 iterations.
Solution → Run Calculation
a. Enter 200 for No. of Iterations and click Calculate.
16.4.9. Simulating Reacting Flow
1. Enable Volumetric for the reacting flow solution.
Physics → Models → Species...
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a. Enable Volumetric and Wall Surface in the Reactions group box.
b. Ensure that Mass Deposition Source is enabled in the Wall Surface Reaction Options group
box.
c. Click OK to close the Species Model dialog box.
2. Retain the default convergence criteria for calculation.
Solution → Reports → Residuals...
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3. Request 200 more iterations.
Solution → Run Calculation → Calculate
4. Compute the mass fluxes.
Results → Reports → Fluxes...
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a. Retain the default selection of Mass Flow Rate in the Options group box.
b. Select outlet, velocity-inlet, and wall-4 from the Boundaries selection list.
In order to properly assess the mass balance, you must account for the mass deposition on the
spinning disk. Hence you select wall-4 in addition to the inlet and outlet boundaries.
c. Click Compute, examine the values displayed in the Results and Net Results boxes, and close
the Flux Reports dialog box.
The net mass imbalance should be a small fraction (for example, 0.5% or less) of the total flux
through the system. If a significant imbalance occurs, you should decrease your residual tolerances by at least an order of magnitude and continue iterating.
5. Display contours of surface deposition rate of ga (Figure 16.3: Contours of Surface Deposition Rate
of Ga (p. 655)).
Results → Graphics → Contours → New...
a. Enter contour-ga-deposition for Contour Name.
b. Select Banded in the Coloring group box.
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c. Select Species... and Surface Deposition Rate of ga from the Contours of drop-down lists.
d. Select wall-4 from the Surfaces selection list.
e. Click Save/Display and close the Contours dialog box.
f.
Disable the Headlight and Lighting options in the View ribbon tab.
Rotate the display with the mouse to obtain the view as shown in (Figure 16.3: Contours of Surface
Deposition Rate of Ga (p. 655)).
Figure 16.3: Contours of Surface Deposition Rate of Ga
6. Reduce the convergence criteria.
Solution → Reports → Residuals...
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a. Enter 5e-06 for Absolute Criteria for continuity.
b. Click OK to close the Residual Monitors dialog box.
7. Request 200 more iterations.
Solution → Run Calculation → Calculate
Figure 16.4: Scaled Residuals
8. Check the mass fluxes.
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Setup and Solution
Results → Reports → Fluxes...
a. Retain the default selection of Mass Flow Rate in the Options group box.
b. Retain the selection of outlet and velocity-inlet and, wall-4 from the Boundaries selection
list.
c. Click Compute, examine the values displayed in the Results and Net Results boxes, and close
the Flux Reports dialog box.
Again, the net mass imbalance should be a small fraction (for example, 0.5% or less) of the
total flux through the system.
9. Save the case and data files (surface-react1.cas.h5 and surface-react1.dat.h5).
File → Write → Case & Data...
16.4.10. Postprocessing the Solution Results
1. Create an iso-surface near wall-4.
Results → Surface → Create → Iso-Surface...
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a. Enter z=0.07 for New Surface Name.
Note:
If you want to delete or otherwise manipulate any surfaces, click Manage... to open
the Surfaces dialog box.
b. Select Mesh... and Z-Coordinate from the Surface of Constant drop-down lists.
c. Click Compute.
The Min and Max fields display the z-extent of the domain.
d. Enter 0.075438 m for Iso-Values.
e. Click Create and close the Iso-Surface dialog box.
The new surface z=0.07 is added to the surfaces selection list.
2. Display contours of temperature on the plane surface created. (Figure 16.5: Temperature Contours
Near wall-4 (p. 660)).
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-temp for Contour Name.
b. Select Banded in the Coloring group box.
c. Select Temperature... and Static Temperature from the Contours of drop-down lists.
d. Select z=0.07 from the Surfaces selection list.
e. Click Save/Display.
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Figure 16.5: Temperature Contours Near wall-4
Figure 16.5: Temperature Contours Near wall-4 (p. 660) shows the temperature distribution across a
plane just above the rotating disk. You can see that the disk has a temperature of 1023 K.
3. Display contours of surface deposition rates of ga (Figure 16.6: Contours of Surface Deposition
Rate of ga (p. 660)).
Results → Graphics → Contours → contour-ga-deposition
Display
Figure 16.6: Contours of Surface Deposition Rate of ga (p. 660) shows the gradient of surface deposition
rate of ga. The maximum deposition is seen at the center of the disk.
Figure 16.6: Contours of Surface Deposition Rate of ga
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Setup and Solution
4. Display contours of surface coverage of ga_s (Figure 16.7: Contours of Surface Coverage of
ga_s (p. 662)).
Results → Graphics → Contours → New...
a. Enter contour-ga_s-coverage for Contour Name.
b. Select Banded in the Coloring group box.
c. Select Species... and Surface Coverage of ga_s from the Contours of drop-down lists.
d. Select wall-4 from the Surfaces selection list.
e. Click Save/Display and close the Contours dialog box.
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Figure 16.7: Contours of Surface Coverage of ga_s
Figure 16.7: Contours of Surface Coverage of ga_s (p. 662) shows the rate of surface coverage of the
site species ga_s.
5. Create a line surface from the center of wall-4 to the edge.
Results → Surface → Create → Line/Rake...
a. Enter the values for x0, x1, y0, y1, z0, and z1 as follows:
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End Points
Value
x0
0
y0
0
z0
0.0762
x1
0.14
y1
0.14
z1
0.0762
You can also select the points by clicking Select Points with Mouse. Then, in the graphic display,
click at the center of wall-4 and at the edge using the right mouse button.
b. Click Create to accept the default name of line-8 for the New Surface Name.
Note:
If you want to delete or otherwise manipulate any surfaces, click Manage... to open
the Surfaces dialog box
c. Close the Line/Rake Surface dialog box.
6. Plot the surface deposition rate of Ga versus radial distance (Figure 16.8: Plot of Surface Deposition
Rate of Ga (p. 664)).
Results → Plots → XY Plot → New...
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a. Enter xy-ga-deposition-radial for Contour Name.
b. Disable Node Values in the Options group box.
c. Select Species... and Surface Deposition Rate of ga from the Y Axis Function drop-down
lists.
The source/sink terms due to the surface reaction are deposited in the cell adjacent to the wall
cells, so it is necessary to plot the cell values and not the node values.
d. Select line-8 you just created from the Surfaces selection list.
e. Click Save/Plot and close the Solution XY Plot dialog box.
The peak surface deposition rate occurs at the center of wall-4 (where the concentration of the mixture
is highest).
Figure 16.8: Plot of Surface Deposition Rate of Ga
Extra:
You can also perform all the postprocessing steps to analyze the deposition of As.
7. Save the case and data files (surface-react2.cas.h5 and surface-react2.dat.h5).
File → Write → Case & Data...
16.5. Summary
The main focus of this tutorial is the accurate modeling of macroscopic gas flow, heat and mass transfer,
species diffusion, and chemical reactions (including surface reactions) in a rotating disk CVD reactor. In
this tutorial, you learned how to use the two-step surface reactions involving site species, and computed
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Summary
simultaneous deposition of gallium and arsenide from a mixture of precursor gases on a rotating susceptor. Note that the same approach is valid if you are simulating multi-step reactions with multiple
sites/site species.
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Chapter 17: Modeling Evaporating Liquid Spray
This tutorial is divided into the following sections:
17.1. Introduction
17.2. Prerequisites
17.3. Problem Description
17.4. Setup and Solution
17.5. Summary
17.1. Introduction
In this tutorial, the air-blast atomizer model in ANSYS Fluent is used to predict the behavior of an
evaporating methanol spray. Initially, the air flow is modeled without droplets. To predict the behavior
of the spray, the discrete phase model is used, including a secondary model for breakup.
This tutorial demonstrates how to do the following:
• Define a spray injection for an air-blast atomizer.
• Calculate a solution using the discrete phase model in ANSYS Fluent.
17.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
17.3. Problem Description
The geometry to be considered in this tutorial is shown in Figure 17.1: Problem Specification (p. 668).
Methanol is cooled to
C before being introduced into an air-blast atomizer. The atomizer contains
an inner air stream surrounded by a swirling annular stream. To make use of the periodicity of the
problem, only a
section of the atomizer will be modeled.
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Figure 17.1: Problem Specification
17.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
17.4.1. Preparation
17.4.2. Mesh
17.4.3. Solver
17.4.4. Models
17.4.5. Materials
17.4.6. Boundary Conditions
17.4.7. Initial Solution Without Droplets
17.4.8. Creating a Spray Injection
17.4.9. Solution
17.4.10. Postprocessing
17.4.1. Preparation
To prepare for running this tutorial:
1.
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Download the evaporate_liquid.zip file here.
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Setup and Solution
2.
Unzip evaporate_liquid.zip to your working directory.
The mesh file sector.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
17.4.2. Mesh
1. Read in the mesh file sector.msh.
File → Read → Mesh...
2. Change the periodic type of periodic-a to rotational.
Setup →
Boundary Conditions →
periodic-a → Edit...
a. Select Rotational in the Periodic Type group box.
b. Click Apply and close the Periodic dialog box.
3. In a similar manner, change the periodic type of periodic-b to rotational.
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4. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and report the progress in the console. Ensure
that the reported minimum volume is a positive number.
5. Display the mesh.
Domain → Mesh → Display...
a. Ensure that Faces is enabled in the Options group box.
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Setup and Solution
b. Select only atomizer-wall, central_air, and swirling_air from the Surfaces selection list.
Tip:
To deselect all surfaces click the far-right button
at the top of the Surfaces
selection list, and then select the desired surfaces from the Surfaces selection list.
c. Click the Colors... button to open the Mesh Colors dialog box.
i.
Select wall from the Types selection list.
ii. Select pink from the Colors selection list.
iii. Close the Mesh Colors dialog box.
d. Click Display and close the Mesh Display dialog box.
The graphics display will be updated to show the mesh. Zoom in with the mouse to obtain the view
shown in Figure 17.2: Air-Blast Atomizer Mesh Display (p. 672).
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Figure 17.2: Air-Blast Atomizer Mesh Display
17.4.3. Solver
Retain the default solver settings of pressure-based steady-state solver in the Solver group of the
Physics tab.
Physics → Solver
17.4.4. Models
1. Enable heat transfer by enabling the energy equation.
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Setup and Solution
Physics → Models → Energy
2. Enable the k-ω SST turbulence model.
Physics → Models → Viscous...
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a. Retain the default selection of k-omega (2 eqn) in the Model list.
b. Retain the default selection of SST in the k-omega Model list.
c. Click OK to close the Viscous Model dialog box.
3. Enable chemical species transport and reaction.
Physics → Models → Species...
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Setup and Solution
a. Select Species Transport in the Model list.
b. Select methyl-alcohol-air from the Mixture Material drop-down list.
The Mixture Material list contains the set of chemical mixtures that exist in the ANSYS Fluent
database. When selecting an appropriate mixture for your case, you can review the constituent
species and the reactions of the predefined mixture by clicking View... next to the Mixture Material drop-down list. The chemical species and their physical and thermodynamic properties are
defined by the selection of the mixture material. After enabling the Species Transport model, you
can alter the mixture material selection or modify the mixture material properties using the Create/Edit Materials dialog box. You will modify your local copy of the mixture material later in this
tutorial.
c. Click OK to close the Species Model dialog box.
17.4.5. Materials
Define materials using the Materials task page.
Setup →
Materials
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1. Remove water vapor and carbon dioxide from the Mixture Species list.
Setup →
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Materials →
Mixture → Create/Edit...
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Setup and Solution
a. Click the Edit button next to the Mixture Species drop-down list to open the Species dialog
box.
i.
Select carbon dioxide (co2) from the Selected Species selection list.
ii. Click Remove to remove carbon dioxide from the Selected Species list.
iii. In a similar manner, remove water vapor (h2o) from the Selected Species list.
iv. Click OK to close the Species dialog box.
b. Click Change/Create and close the Create/Edit Materials dialog box.
Note:
It is good practice to click the Change/Create button whenever changes are made
to material properties even though it is not necessary in this case.
17.4.6. Boundary Conditions
Specify boundary conditions using the Boundary Conditions task page.
Setup →
Boundary Conditions
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1. Set the boundary conditions for the inner air stream (central_air).
Setup →
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Boundary Conditions →
central_air → Edit...
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Setup and Solution
a. Enter 9.167e-5 kg/s for Mass Flow Rate.
b. Enter 0 for X-Component of Flow Direction.
c. Retain the default value of 0 for Y-Component of Flow Direction.
d. Enter 1 for Z-Component of Flow Direction.
e. Select Intensity and Hydraulic Diameter from the Specification Method drop-down list.
f.
Enter 10 for Turbulent Intensity.
g. Enter 0.0037 m for Hydraulic Diameter.
h. Click the Thermal tab and enter 293 K for Total Temperature.
i.
Click the Species tab and enter 0.23 for o2 in the Species Mass Fractions group box.
j.
Click Apply and close the Mass-Flow Inlet dialog box.
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2. Set the boundary conditions for the air stream surrounding the atomizer (co-flow-air).
Setup →
Boundary Conditions →
co-flow-air → Edit...
a. Enter 1 m/s for Velocity Magnitude.
b. Select Intensity and Hydraulic Diameter from the Specification Method drop-down list.
c. Retain the default value of 5 for Turbulent Intensity.
d. Enter 0.0726 m for Hydraulic Diameter.
e. Click the Thermal tab and enter 293 K for Temperature.
f.
Click the Species tab and enter 0.23 for o2 in the Species Mass Fractions group box.
g. Click Apply and close the Velocity Inlet dialog box.
3. Set the boundary conditions for the exit boundary (outlet).
Setup →
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Boundary Conditions →
outlet → Edit...
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Setup and Solution
a. Select From Neighboring Cell from the Backflow Direction Specification Method drop-down
list.
b. Retain Intensity and Viscosity Ratio from the Specification Method drop-down list.
c. Retain the default value of 5 for Backflow Turbulent Intensity (%).
d. Enter 5 for Backflow Turbulent Viscosity Ratio.
e. Click the Thermal tab and enter 293 K for Backflow Total Temperature.
f.
Click the Species tab and enter 0.23 for o2 in the Species Mass Fractions group box.
g. Click Apply and close the Pressure Outlet dialog box.
4. Set the boundary conditions for the swirling annular stream (swirling_air).
Setup →
Boundary Conditions →
swirling_air → Edit...
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a. Select Magnitude and Direction from the Velocity Specification Method drop-down list.
b. Enter 19 m/s for Velocity Magnitude.
c. Select Cylindrical (Radial, Tangential, Axial) from the Coordinate System drop-down list.
d. Enter 0 for Radial-Component of Flow Direction.
e. Enter 0.7071 for Tangential-Component of Flow Direction.
f.
Enter 0.7071 for Axial-Component of Flow Direction.
g. Select Intensity and Hydraulic Diameter from the Specification Method drop-down list.
h. Retain the default value of 5 for Turbulent Intensity.
i.
Enter 0.0043 m for Hydraulic Diameter.
j.
Click the Thermal tab and enter 293 K for Temperature.
k. Click the Species tab and enter 0.23 for o2 in the Species Mass Fractions group box.
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Setup and Solution
l.
Click Apply and close the Velocity Inlet dialog box.
5. Set the boundary conditions for the outer wall of the atomizer (outer-wall).
Setup →
Boundary Conditions →
outer-wall → Edit...
a. Select Specified Shear in the Shear Condition list.
b. Retain the default values for the remaining parameters.
c. Click Apply and close the Wall dialog box.
17.4.7. Initial Solution Without Droplets
The airflow will first be solved and analyzed without droplets.
1. Set the solution method.
Solution → Solution → Methods...
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Modeling Evaporating Liquid Spray
Retain the default selections.
2. Retain the default under-relaxation factors.
Solution → Controls → Controls...
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Setup and Solution
3. Enable residual plotting during the calculation.
Solution → Reports → Residuals...
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Modeling Evaporating Liquid Spray
a. Ensure that Plot is enabled in the Options group box.
b. Click OK to close the Residual Monitors dialog box.
4. Initialize the flow field.
Solution → Initialization
a. Retain the Method at the default of Hybrid.
b. Click Initialize to initialize the variables.
Note:
For flows in complex topologies, hybrid initialization will provide better initial velocity
and pressure fields than standard initialization. This will help to improve the convergence
behavior of the solver.
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Setup and Solution
5. Save the case file (spray1.cas.h5).
File → Write → Case...
6. Start the calculation by requesting 150 iterations.
Solution →
Run Calculation
a. Select User Specified from the Time Step Method group box.
b. Retain 1 s for Pseudo Time Step Size.
c. Enter 150 for Number of Iterations.
d. Click Calculate.
Figure 17.3: Scaled Residuals
7. Save the case and data files (spray1.cas.h5 and spray1.dat.h5).
File → Write → Case & Data...
Note:
ANSYS Fluent will ask you to confirm that the previous case file is to be overwritten.
8. Create a clip plane to examine the flow field at the midpoint of the atomizer section.
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Modeling Evaporating Liquid Spray
Results → Surface → Create → Iso-Surface...
a. Enter angle=15 for New Surface Name.
b. Select Mesh... and Angular Coordinate from the Surface of Constant drop-down lists.
c. Click Compute to obtain the minimum and maximum values of the angular coordinate.
d. Enter 15 for Iso-Values.
e. Click Create to create the isosurface.
f.
Close the Iso-Surface dialog box.
9. Review the current state of the solution by examining contours of velocity magnitude (Figure 17.4: Velocity Magnitude at Mid-Point of Atomizer Section (p. 690)).
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-vel for Contour Name.
b. Select Banded in the Coloring group box.
c. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
d. Enable Draw Mesh.
The Mesh Display dialog box will open.
i.
Retain the current mesh display settings.
ii. Close the Mesh Display dialog box.
e. Select angle=15 from the Surfaces selection list.
f.
Click Save/Display and close the Contours dialog box.
g. Use the mouse to obtain the view shown in Figure 17.4: Velocity Magnitude at Mid-Point of
Atomizer Section (p. 690).
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Figure 17.4: Velocity Magnitude at Mid-Point of Atomizer Section
10. Modify the view to include the entire atomizer.
View → Display → Views...
a. Click the Define... button under Periodic Repeats to open the Graphics Periodicity dialog
box.
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Setup and Solution
i.
Select fluid from the Cell Zones selection list.
ii. Retain the selection of Rotational in the Periodic Type list.
iii. Retain the value of 12 for Number of Repeats.
iv. Click Set and close the Graphics Periodicity dialog box.
The graphics display will be updated to show the entire atomizer.
b. Click Apply and close the Views dialog box.
11. Display pathlines of the air in the swirling annular stream (Figure 17.5: Pathlines of Air in the
Swirling Annular Stream (p. 693)).
Results → Graphics → Pathlines → New...
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Modeling Evaporating Liquid Spray
a. Enter pathlines-air for Pathline Name.
b. Increase the Path Skip value to 5.
c. In the Release from Surfaces filter, type s to display the surface names that begin with s and
select swirling_air from the selection list.
d. Enable Draw Mesh in the Options group box.
The Mesh Display dialog box will open.
i.
Retain the current mesh display settings.
ii. Close the Mesh Display dialog box.
e. Click Save/Display and close the Pathlines dialog box.
f.
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Use the mouse to obtain the view shown in Figure 17.5: Pathlines of Air in the Swirling Annular
Stream (p. 693).
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Setup and Solution
Figure 17.5: Pathlines of Air in the Swirling Annular Stream
17.4.8. Creating a Spray Injection
1. Define the discrete phase modeling parameters.
Physics → Models → Discrete Phase...
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a. Select Interaction with Continuous Phase in the Interaction group box.
This will include the effects of the discrete phase trajectories on the continuous phase.
b. Retain the value of 10 for DPM Iteration Interval.
c. Select Mean Values in the Contour Plots for DPM Variables group box.
This will make the cell-averaged variables available for postprocessing activities.
d. Select the Unsteady Particle Tracking option in the Particle Treatment group box.
e. Enter 0.0001 for Particle Time Step Size.
f.
Enter 10 for Number of Time Steps.
g. Under the Physical Models tab, enable Temperature Dependent Latent Heat and Breakup
in the Options group box.
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Setup and Solution
h. Under the Numerics tab, select Linearize Source Terms (Source Terms group).
Enabling this option will allow you to run the simulation with more aggressive setting for the
Discrete Phase Sources under-relaxation factor to speed up the solution convergence.
i.
Click Injections... to open the Injections dialog box.
In this step, you will define the characteristics of the atomizer.
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An Information dialog box appears indicating that the Max. Number of Steps has been
changed from 50000 to 500. Click OK in the Information dialog box to continue.
j.
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Click the Create button to create the spray injection.
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Setup and Solution
k. In the Set Injection Properties dialog box, select air-blast-atomizer from the Injection Type
drop-down list.
l.
Enter 600 for Number of Streams.
This option controls the number of droplet parcels that are introduced into the domain at every
time step.
m. Select Droplet in the Particle Type group box.
n. Select methyl-alcohol-liquid from the Material drop-down list.
o. In the Point Properties tab, specify point properties for particle injections.
i.
Retain the default values of 0 and 0 for X-Position and Y-Position.
ii. Enter 0.0015 for Z-Position.
iii. Retain the default values of 0, 0, and 1 for X-Axis, Y-Axis, and Z-Axis, respectively.
iv. Enter 263 K for Temperature.
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Scroll down the list to see the remaining point properties.
v. Enter 8.5e-5 kg/s for Flow Rate.
This is the methanol flow rate for a 30-degree section of the atomizer. The actual atomizer flow
rate is 12 times this value.
vi. Retain the default Start Time of 0 s and enter 100 s for the Stop Time.
For this problem, the injection should begin at
and not stop until long after the time period
of interest. A large value for the stop time (for example, 100 s) will ensure that the injection will
essentially never stop.
vii. Enter 0.0035 m for the Injector Inner Diameter and 0.0045 m for the Injector Outer
Diameter.
viii.Enter 45 degrees for Spray Half Angle.
The spray angle is the angle between the liquid sheet trajectory and the injector centerline.
ix. Enter 82.6 m/s for the Relative Velocity.
The relative velocity is the expected relative velocity between the atomizing air and the liquid
sheet.
x. Retain the default Azimuthal Start Angle of 0 degrees and enter 30 degrees for the Azimuthal Stop Angle.
This will restrict the injection to the 30-degree section of the atomizer that is being modeled.
p. In the Physical Models tab, specify the breakup model and drag parameters.
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i.
In the Breakup group, ensure that Enable Breakup is selected and TAB is selected from
the Breakup Model drop-down list.
ii. Retain the default values of 0 for y0 and 2 for Breakup Parcels.
iii. In the Drag Parameters group box, select dynamic-drag from the Drag Law drop-down
list.
The dynamic-drag law is available only when the Breakup model is used.
q. In the Turbulent Dispersion tab, define the turbulent dispersion.
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i.
Enable Discrete Random Walk Model and Random Eddy Lifetime in the Stochastic
Tracking group box.
These models will account for the turbulent dispersion of the droplets.
ii. Click OK to close the Set Injection Properties dialog box.
Note:
To modify the existing injection, select its name in the Injections list and click
Set..., or simply double-click the injection of interest.
r.
Close the Injections dialog box.
Note:
In the case that the spray injection would be striking a wall, you should specify the
wall boundary conditions for the droplets. Though this tutorial does have wall zones,
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Setup and Solution
they are a part of the atomizer apparatus. You need not change the wall boundary
conditions any further because these walls are not in the path of the spray droplets.
s. Click OK to close the Discrete Phase Model dialog box.
2. Specify the droplet material properties.
Setup →
Materials →
methyl-alcohol-liquid → Create/Edit...
When secondary atomization models (such as Breakup) are used, several droplet properties need to
be specified.
a. Ensure droplet-particle is selected in the Material Type drop-down list.
b. Enter 0.00095 kg/m-s for Viscosity in the Properties group box.
c. Ensure that piecewise-linear is selected from the Saturation Vapor Pressure drop-down list.
Scroll down to find the Saturation Vapor Pressure drop-down list.
d. Click the Edit... button next to Saturation Vapor Pressure to open the Piecewise-Linear
Profile dialog box.
e. Retain the default values and click OK to close the Piecewise-Linear Profile dialog box.
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f.
Select convection/diffusion-controlled from the Vaporization/Boiling Model drop-down
list.
g. Click OK to close the Convection/Diffusion Model dialog box.
h. Click Change/Create to accept the change in properties for the methanol droplet material
and close the Create/Edit Materials dialog box.
17.4.9. Solution
1. Increase the under-relaxation factor for Discrete Phase Sources.
Solution → Controls → Controls...
In the Pseudo Transient Explicit Relaxation Factors group box, change the under-relaxation
factor for Discrete Phase Sources to 0.9.
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2. Remove the convergence criteria.
Solution → Reports → Residuals...
a. Enable Show Advanced Options and select none from the Convergence Criterion dropdown list.
b. Click OK to close the Residual Monitors dialog box.
3. Enable the plotting of mass fraction of ch3oh.
Solution → Reports → Definitions → New → Surface Report → Mass-Weighted Average...
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a. Enter ch3oh_outlet for Name of the surface report definition.
b. In the Create group box, enable Report Plot and Print to Console.
c. Select Species... and Mass fraction of ch3oh from the Field Variable drop-down lists.
d. Select outlet from the Surfaces selection list.
e. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
Fluent automatically generates the ch3oh_outlet-rplot report plot under the Solution/Monitors/Report Plots tree branch.
4. Enable the plotting of the sum of the DPM Mass Source.
Solution → Reports → Definitions → New → Volume Report → Sum...
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a. Enter dpm-mass-source for Name.
b. In the Create group box, enable Report Plot and Print to Console.
c. Select Discrete Phase Sources... and DPM Mass Source from the Field Variable drop-down
lists.
d. Select fluid from the Cell Zones selection list.
e. Click OK to save the volume report definition settings and close the Volume Report Definition
dialog box.
Fluent automatically generates the dpm-mass-source-rplot report plot under Solution/Monitors/Report Plots tree branch.
f.
Modify the attributes of the dpm-mass-source-rplot report plot axes.
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Solution → Monitors → Report Plots → dpm-mass-source-rplot
i.
Edit...
In the Plot Window group box, click the Axes... button to open the Axes dialog box.
ii. Select Y in the Axis list.
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Setup and Solution
iii. Select exponential from the Type drop-down list.
iv. Set Precision to 2.
v. Click Apply and close the Axes dialog box.
vi. Click OK to close the Edit Report Plot dialog box.
5. Create a DPM report definition for tracking the total mass present in the domain.
Solution → Reports → Definitions → New → DPM Report → Mass in Domain...
a. Enter dpm-mass-in-domain for Name.
b. In the Create group box, enable Report Plot and Print to Console.
c. Select injection-0 from the Injections selection list.
d. Disable Show Mass Flow / Change Rate.
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e. Click OK to save the volume report definition settings and close the DPM Report Definition
dialog box.
Fluent automatically generates the dpm-mass-in-domain-rplot report plot under Solution/Monitors/Report Plots tree branch.
f.
Modify the attributes of the dpm-mass-in-domain-rplot report plot axes (in a manner similar
to that for the dpm-mass-source-rplot plot).
Solution → Monitors → Report Plots → dpm-mass-in-domain-rplot
i.
Edit...
In the Plot Window group box, click the Axes... button to open the Axes dialog box.
ii. Select Y in the Axis list.
iii. Select exponential from the Type drop-down list.
iv. Set Precision to 2.
v. Click Apply and close the Axes dialog box.
vi. Click OK to close the Edit Report Plot dialog box.
6. Create a DPM report definition for tracking the mass of the evaporated particles.
Solution → Reports → Definitions → New → DPM Report → Evaporated Mass...
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Setup and Solution
a. Enter dpm-evaporated-mass for Name.
b. In the Create group box, enable Report Plot and Print to Console.
c. Select injection-0 from the Injections selection list.
d. Ensure that the Show Mass Flow / Change Rate option is selected.
e. Click OK to save the volume report definition settings and close the DPM Report Definition
dialog box.
Fluent automatically generates the dpm-evaporated-mass-rplot report plot under Solution/Monitors/Report Plots tree branch.
f.
Modify the attributes of the dpm-evaporated-mass-rplot report plot axes in a manner similar
to that for the dpm-mass-source-rplot plot.
7. Request 300 more iterations (Figure 17.6: Convergence History of Mass Fraction of ch3oh on Fluid (p. 710), Figure 17.7: Convergence History of DPM Mass Source on Fluid (p. 710), Figure 17.8: Convergence History of Total Mass in Domain (p. 711), and Figure 17.9: Convergence History of Evaporated Particle Mass (p. 711)).
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Solution → Run Calculation
It can be concluded that the solution is converged because the number of particle tracks are constant
and the flow variable plots are flat.
Figure 17.6: Convergence History of Mass Fraction of ch3oh on Fluid
Figure 17.7: Convergence History of DPM Mass Source on Fluid
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Setup and Solution
Figure 17.8: Convergence History of Total Mass in Domain
Figure 17.9: Convergence History of Evaporated Particle Mass
8. Save the case and data files (spray2.cas.h5 and spray2.dat.h5).
File → Write → Case & Data...
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17.4.10. Postprocessing
1. Display the trajectories of the droplets in the spray injection (Figure 17.10: Particle Tracks for the
Spray Injection (p. 713)).
This will allow you to review the location of the droplets.
Results → Graphics → Particle Tracks → New...
a. Enter particle-tracks-droplets for Particle Tracks Name.
b. Enable Draw Mesh in the Options group box.
The Mesh Display dialog box will open.
i.
Retain the current display settings.
ii. Close the Mesh Display dialog box.
c. Retain the default selection of point from the Track Style drop-down list.
d. Select Particle Variables... and Particle Diameter from the Color by drop-down lists.
This will display the location of the droplets colored by their diameters.
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Setup and Solution
e. Select injection-0 from the Release from Injections selection list.
f.
Click Save/Display.
As an optional exercise, you can increase the particle size by clicking the Attributes... button in
the Particle Tracks dialog box and adjusting the Marker Size value in the Track Style Attributes
dialog box.
g. Close the Particle Tracks dialog box.
h. Restore the 30–degree section to obtain the view as shown in Figure 17.10: Particle Tracks for
the Spray Injection (p. 713).
View → Display → Views...
i.
Click the Define... button to open the Graphics Periodicity dialog box.
ii. Click Reset and close the Graphics Periodicity dialog box.
iii. Close the Views dialog box.
i.
Use the mouse to obtain the view shown in Figure 17.10: Particle Tracks for the Spray Injection (p. 713).
Figure 17.10: Particle Tracks for the Spray Injection
The air-blast atomizer model assumes that a cylindrical liquid sheet exits the atomizer, which then
disintegrates into ligaments and droplets. Appropriately, the model determines that the droplets should
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be input into the domain in a ring. The radius of this disk is determined from the inner and outer radii
of the injector.
Note:
The maximum diameter of the droplets is about 4.9x10–5 m or 0.49 mm, which is
simililar to the film height. The inner diameter and outer diameter of the injector are
3.5 mm and 4.5 mm, respectively. Hence the film height is 0.5 mm. The range in the
droplet sizes is due to the fact that the air-blast atomizer automatically uses a distribution of droplet sizes.
Also note that the droplets are placed a slight distance away from the injector. Once
the droplets are injected into the domain, their behavior will be determined by secondary models. For instance, they may collide/coalesce with other droplets depending on
the secondary models employed. However, once a droplet has been introduced into
the domain, the air-blast atomizer model no longer affects the droplet.
2. Display the mean particle temperature field (Figure 17.11: Contours of DPM Temperature (p. 715)).
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-dpm-temp for Contour Name.
b. Ensure that Filled is enabled in the Options group box.
c. Select Banded in the Coloring group box.
d. Select Discrete Phase Variables... and DPM Temperature from the Contours of drop-down
lists.
e. Disable Auto Range.
The Clip to Range option will automatically be enabled.
f.
Click Compute to update the Min and Max fields.
g. Enter 260 for Min.
h. Select angle=15 from the Surfaces selection list.
i.
Click Save/Display and close the Contours dialog box.
j.
Use the mouse to obtain the view shown in Figure 17.11: Contours of DPM Temperature (p. 715).
Figure 17.11: Contours of DPM Temperature
3. Display the mean Sauter diameter (Figure 17.12: Contours of DPM Sauter Diameter (p. 716)).
Results → Graphics → Contours → New...
a. Enter contour-dpm-sauter-diameter for Contour Name.
b. Ensure that Filled is enabled in the Options group box.
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c. Select Banded in the Coloring group box.
d. Select Discrete Phase Variables... and DPM D32 from the Contours of drop-down lists.
e. Select angle=15 from the Surfaces selection list.
f.
Click Save/Display and close the Contours dialog box.
Figure 17.12: Contours of DPM Sauter Diameter
4. Display vectors of DPM mean velocity colored by DPM velocity magnitude (Figure 17.13: Vectors
of DPM Mean Velocity Colored by DPM Velocity Magnitude (p. 718)).
Results → Graphics → Vectors → New...
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Setup and Solution
a. Enter vector-dpm-vel for Vector Name.
b. Select dpm-mean-velocity from the Vectors of drop-down lists.
c. Select Discrete Phase Variables... and DPM Velocity Magnitude from the Color by dropdown lists.
d. Select arrow from the Style drop-down list.
e. Enter 7 for Scale.
f.
Select angle=15 from the Surfaces selection list.
g. Click Save/Display and close the Contours dialog box.
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Figure 17.13: Vectors of DPM Mean Velocity Colored by DPM Velocity Magnitude
5. Create an isosurface of the methanol mass fraction.
Results → Surface → Create → Iso-Surface...
a. Enter methanol-mf=0.002 for the New Surface Name.
b. Select Species... and Mass fraction of ch3oh from the Surface of Constant drop-down lists.
c. Click Compute to update the minimum and maximum values.
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Setup and Solution
d. Enter 0.002 for Iso-Values.
e. Click Create and then close the Iso-Surface dialog box.
6. Display the isosurface you just created (methanol-mf=0.002).
Results → Graphics → Mesh → New...
a. Deselect atomizer-wall and select methanol-mf=0.002 in the Surfaces selection list.
b. Click the Colors... button to open the Mesh Colors dialog box.
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i.
Select surface in the Types list and green in the Colors list.
Scroll down the Types list to locate surface. The isosurface will now be displayed in green,
which contrasts better with the rest of the mesh.
ii. Close the Mesh Colors dialog box.
c. Click Display in the Mesh Display dialog box.
The graphics display will be updated to show the isosurface.
7. Modify the view to include the entire atomizer.
View → Display → Views...
a. Click Define... to open the Graphics Periodicity dialog box.
i.
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Setup and Solution
ii. Ensure that Rotational is selected from the Periodic Type list and the Number of Repeats
is set to 12.
iii. Click Set and close the Graphics Periodicity dialog box.
b. Click Apply and close the Views dialog box.
c. Click Display and close the Mesh Display dialog box.
d. Use the mouse to obtain the view shown in Figure 17.14: Full Atomizer Display with Surface
of Constant Methanol Mass Fraction (p. 721).
Figure 17.14: Full Atomizer Display with Surface of Constant Methanol Mass Fraction
e. This view can be improved to resemble Figure 17.15: Atomizer Display with Surface of Constant
Methanol Mass Fraction Enhanced (p. 722) by changing some of the following variables:
• Disable Edges in the Mesh Display dialog box
• Select only atomizer-wall and methanol-mf=0.002 in the Surfaces list of the
Mesh Display dialog box
• Change the Number of Repeats to 6 in the Graphics Periodicity dialog box
• Enable Lighting and change it to Flat in the View tab (Display group)
• Enable Headlight check in the View tab (Display group)
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Figure 17.15: Atomizer Display with Surface of Constant Methanol Mass Fraction Enhanced
8. Save the case and data files (spray3.cas.h5 and spray3.dat.h5).
File → Write → Case & Data...
17.5. Summary
In this tutorial, a spray injection was defined for an air-blast atomizer and the solution was calculated
using the discrete phase model in ANSYS Fluent. The location of methanol droplet particles after exiting
the atomizer and an isosurface of the methanol mass fraction were examined.
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Chapter 18: Using the VOF Model
This tutorial is divided into the following sections:
18.1. Introduction
18.2. Prerequisites
18.3. Problem Description
18.4. Setup and Solution
18.5. Summary
18.1. Introduction
This tutorial examines the flow of ink as it is ejected from the nozzle of a printhead in an inkjet printer.
Using ANSYS Fluent’s volume of fluid (VOF) multiphase modeling capability, you will be able to predict
the shape and motion of the resulting droplets in an air chamber.
This tutorial demonstrates how to do the following:
• Set up and solve a transient problem using the pressure-based solver and VOF model.
• Copy material from the property database.
• Define time-dependent boundary conditions with an expression.
• Patch initial conditions in a subset of the domain.
• Automatically save data files at defined points during the solution.
• Examine the flow and interface of the two fluids using volume fraction contours.
18.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
18.3. Problem Description
The problem considers the transient tracking of a liquid-gas interface in the geometry shown in Figure 18.1: Schematic of the Problem (p. 724). The axial symmetry of the problem enables a 2D geometry
to be used. The computation mesh consists of 24,600 cells. The domain consists of two regions: an ink
chamber and an air chamber. The dimensions are summarized in Table 18.1: Ink Chamber Dimensions (p. 724).
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Figure 18.1: Schematic of the Problem
Table 18.1: Ink Chamber Dimensions
Ink Chamber, Cylindrical Region: Radius (mm)
0.015
Ink Chamber, Cylindrical Region: Length (mm)
0.050
Ink Chamber, Tapered Region: Final Radius (mm)
0.009
Ink Chamber, Tapered Region: Length (mm)
0.050
Air Chamber: Radius (mm)
0.030
Air Chamber: Length (mm)
0.280
The following is the chronology of events modeled in this simulation:
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Setup and Solution
• At time zero, the nozzle is filled with ink, while the rest of the domain is filled with air. Both fluids
are assumed to be at rest. To initiate the ejection, the ink velocity at the inlet boundary (which is
modeled in this simulation by a user-defined function) suddenly increases from 0 to 3.58 m/s and
then decreases according to a cosine law.
• After 10 microseconds, the velocity returns to zero.
The calculation is run for 30 microseconds overall, that is, three times longer than the duration of the
initial impulse.
Because the dimensions are small, the double-precision version of ANSYS Fluent will be used. Air will
be designated as the primary phase, and ink (which will be modeled with the properties of liquid water)
will be designated as the secondary phase. Patching will be required to fill the ink chamber with the
secondary phase. Gravity will not be included in the simulation. To capture the capillary effect of the
ejected ink, the surface tension and prescription of the wetting angle will be specified. The surface inside
the nozzle will be modeled as neutrally wettable, while the surface surrounding the nozzle orifice will
be non-wettable.
18.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
18.4.1. Preparation
18.4.2. Reading and Manipulating the Mesh
18.4.3. General Settings
18.4.4. Models
18.4.5. Materials
18.4.6. Phases
18.4.7. Operating Conditions
18.4.8. Boundary Conditions
18.4.9. Solution
18.4.10. Postprocessing
18.4.1. Preparation
To prepare for running this tutorial:
1.
Download the vof.zip file here.
2.
Unzip vof.zip to your working directory.
The mesh file inkjet.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
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Using the VOF Model
6.
Enable Double Precision under Options.
Note:
The double precision solver is recommended for modeling multiphase flows simulation.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
18.4.2. Reading and Manipulating the Mesh
1. Read the mesh file inkjet.msh.
File → Read → Mesh...
A warning message will be displayed twice in the console. You need not take any action at this point,
as the issue will be resolved when you define the solver settings in General Settings (p. 730).
2. Examine the mesh (Figure 18.2: Default Display of the Nozzle Mesh (p. 726)).
Figure 18.2: Default Display of the Nozzle Mesh
Tip:
By zooming in with the middle mouse button, you can see that the interior of the
model is composed of a fine mesh of quadrilateral cells (see Figure 18.3: The Quadrilateral Mesh (p. 727)).
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Setup and Solution
Figure 18.3: The Quadrilateral Mesh
3. Set graphics display options
View → Display → Options...
a. Ensure that All is selected from the Animation Option drop-down list.
Selecting All will allow you to see the movement of the entire mesh as you manipulate the Camera
view in the next step.
4. Click Apply and close the Display Options dialog box.
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5. Manipulate the mesh display to show the full chamber upright.
View → Display → Views...
a. Select front from the Views selection list.
b. Select axis from the Mirror Planes selection list.
c. Click Apply.
The mesh display is updated to show both sides of the chamber.
d. Click the Camera... button to open the Camera Parameters dialog box.
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Setup and Solution
Note:
You may notice that the scale of the dimensions in the Camera Parameters dialog
box appear very large given the problem dimensions. This is because you have not
yet scaled the mesh to the correct units. You will do this in a later step.
i.
Drag the indicator of the dial with the left mouse button in the clockwise direction until
the upright view is displayed (Figure 18.4: Mesh Display of the Nozzle Mirrored and Upright (p. 730)).
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Figure 18.4: Mesh Display of the Nozzle Mirrored and Upright
ii. Click Apply and close the Camera Parameters dialog box.
e. Close the Views dialog box.
18.4.3. General Settings
1. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and report the progress in the console. Make
sure that the reported minimum volume is a positive number.
2. Scale the mesh.
Domain → Mesh → Scale...
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Setup and Solution
a. Select Specify Scaling Factors from the Scaling group box.
b. Enter 1e-6 for X and Y in the Scaling Factors group box.
c. Click Scale and close the Scale Mesh dialog box.
3. a. Right click in the graphics window and select Refresh Display
b. Click the Fit to Window icon,
, to center the graphic in the window.
4. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
Note:
It is a good idea to check the mesh after you manipulate it (that is, scale, convert to
polyhedra, merge, separate, fuse, add zones, or smooth and swap.) This will ensure that
the quality of the mesh has not been compromised.
5. Define the units for the mesh.
Domain → Mesh → Units...
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Using the VOF Model
a. Select length from the Quantities list.
b. Select mm from the Units list.
c. Select surface-tension from the Quantities list.
d. Select dyn/cm from the Units list.
e. Close the Set Units dialog box.
6. Retain the default setting of Pressure-Based in the Solver group box of the General task page.
Setup →
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Setup and Solution
7. Select Transient from the Time list.
8. Select Axisymmetric in the Solver group box.
18.4.4. Models
1. Enable the laminar viscous model.
Physics → Models → Viscous...
a. Select Laminar in the Model group box.
b. Click OK to close the Viscous Model dialog box.
2. Enable the Volume of Fluid multiphase model.
Physics → Models → Multiphase...
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a. Select Volume of Fluid from the Model list.
The Multiphase Model dialog box expands to show related inputs.
b. Retain the default settings and click Apply and then Close to close the Multiphase Model
dialog box.
Important:
When setting up your case, if you have made changes in the current tab, you should
click the Apply button to make them effective before moving to the next tab.
Otherwise, the relevant models may not be available in the other tabs, and your
settings may be lost.
18.4.5. Materials
The default properties of air and water defined in ANSYS Fluent are suitable for this problem. In this step,
you will make sure that both materials are available for selection in later steps.
1. Add water to the list of fluid materials by copying it from the ANSYS Fluent materials database.
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Setup and Solution
Physics → Materials → Create/Edit...
a. Click Fluent Database... in the Create/Edit Materials dialog box to open the Fluent Database
Materials dialog box.
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i.
Select water-liquid (h2o < l >) from the Fluent Fluid Materials selection list.
Scroll down the Fluent Fluid Materials list to locate water-liquid (h2o < l >).
ii. Click Copy to copy the information for water to your list of fluid materials.
iii. Close the Fluent Database Materials dialog box.
b. Click Change/Create and close the Create/Edit Materials dialog box.
18.4.6. Phases
In the following steps, you will define water as the secondary phase. When you define the initial solution,
you will patch water in the nozzle region. In general, you can specify the primary and secondary phases
whichever way you prefer. It is a good idea to consider how your choice will affect the ease of problem
setup, especially with more complicated problems.
Physics → Models → Multiphase...
In the Multiphase Model dialog box, open the Phases tab.
1. Specify air (air) as the primary phase.
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Setup and Solution
a. Select phase-1 – Prmary Phase in the Phases selection list.
b. Enter air for Name.
c. Retain the default selection of air in the Phase Material drop-down list.
d. Click Apply
2. Specify water (water-liquid) as the secondary phase.
a. In the Phases selection list, select phase-2 – Secondary Phase.
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Using the VOF Model
b. Enter water-liquid for Name.
c. Select water-liquid from the Phase Material drop-down list.
d. Click Apply.
3. Specify the interphase interaction.
In the Multiphase Model dialog box, open the Phase Interaction tab.
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Setup and Solution
a. In the Force tab, select Surface Tension Force Modeling (Global Options group box).
The surface tension inputs is displayed and the Continuum Surface Force model is set as the default.
b. Enable Wall Adhesion (Adhesion Options group box) so that contact angles can be prescribed.
c. For Surface Tension Coefficient (Force Setup group box), select constant from the dropdown list and enter 73.5 dyn/cm .
d. Click Apply.
4. Close the Multiphase Model dialog box.
18.4.7. Operating Conditions
1. Set the operating reference pressure location.
Setup →
Boundary Conditions → Operating Conditions...
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Using the VOF Model
You will set the Reference Pressure Location to be a point where the fluid will always be 100
air.
a. Enter 0.10 mm for X.
b. Enter 0.03 mm for Y.
c. Click OK to close the Operating Conditions dialog box.
18.4.8. Boundary Conditions
1. Set the boundary conditions at the inlet (inlet) for the mixture by selecting mixture from the
Phase drop-down list in the Boundary Conditions task page.
Setup → Boundary Conditions → Inlet → inlet
Edit...
a. Select expression from the Velocity Magnitude drop-down list.
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Setup and Solution
b. Enter the expression in the Expression Editor dialog box as shown and click OK and close
the dialog box.
IF(t<=10e-06[sec],3.58[m/s]*cos(PI*t/30e-6[s]),0[m/s])
c. Click Apply to close the Velocity Inlet dialog box.
2. Set the boundary conditions at the inlet (inlet) for the secondary phase by selecting water-liquid
from the Phase drop-down list in the Boundary Conditions task page.
Setup → Boundary Conditions → Inlet → inlet → water-liquid
Edit...
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a. Click the Multiphase tab and enter 1 for the Volume Fraction.
b. Click Apply and close the Velocity Inlet dialog box.
3. Set the boundary conditions at the outlet (outlet) for the secondary phase by selecting water-liquid
from the Phase drop-down list in the Boundary Conditions task page.
Setup → Boundary Conditions → Outlet → outlet → water-liquid
Edit...
a. Click the Multiphase tab and retain the default setting of 0 for the Backflow Volume Fraction.
b. Click Apply and close the Pressure Outlet dialog box.
4. Set the conditions at the top wall of the air chamber (wall_no_wet) for the mixture by selecting
mixture from the Phase drop-down list in the Boundary Conditions task page.
Setup → Boundary Conditions → Wall → wall_no_wet
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Edit...
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Setup and Solution
a. Enter 175 degrees for Contact Angles.
b. Click Apply and close the Wall dialog box.
Note:
This angle affects the dynamics of droplet formation. You can repeat this simulation
to find out how the result changes when the wall is hydrophilic (that is, using a
small contact angle, say 10 degrees).
5. Set the conditions at the side wall of the ink chamber (wall_wet) for the mixture.
Setup → Boundary Conditions → Wall → wall_wet
Edit...
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a. Retain the default setting of 90 degrees for Contact Angles.
b. Click Apply and close the Wall dialog box.
18.4.9. Solution
1. Set the solution methods.
Solution → Solution → Methods...
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Setup and Solution
a. Enable Non-Iterative Time Advancement.
The non-iterative time advancement (NITA) scheme is often advantageous compared to the iterative
schemes as it is less CPU intensive. Although smaller time steps must be used with NITA compared
to the iterative schemes, the total CPU expense is often smaller. If the NITA scheme leads to convergence difficulties, then the iterative schemes (for example, PISO, SIMPLE) should be used instead.
b. Select Fractional Step from the Scheme drop-down list in the Pressure-Velocity Coupling
group box.
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c. Retain the default selection of Least Squares Cell Based from the Gradient drop-down list
in the Spatial Discretization group box.
d. Retain the default selection of PRESTO! from the Pressure drop-down list.
e. Select QUICK from the Momentum drop-down list.
f.
Select Compressive from the Volume-Fraction drop-down list.
2. Enable the plotting of residuals during the calculation.
Solution → Reports → Residuals...
a. Ensure Plot is selected in the Options group box.
b. Click OK to close the Residual Monitors dialog box.
3. Initialize the solution after reviewing the default initial values.
Solution → Initialization → Options...
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Setup and Solution
a. Retain the default settings for all the parameters and click Initialize (either in the ribbon or
in the Solution Initialization task page.
4. Define a register for the ink chamber region.
Solution → Cell Registers
New → Region...
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Setup and Solution
a. Enter a setting of 0 mm for X Min and Y Min in the Input Coordinates group box.
b. Enter 0.10 mm for X Max.
c. Enter 0.03 mm for Y Max.
d. Click Save and close the Region Register dialog box.
5. Patch the initial distribution of the secondary phase (water-liquid).
Solution → Initialization → Patch...
a. Select water-liquid from the Phase drop-down list.
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b. Select Volume Fraction from the Variable list.
c. Enter 1 for Value.
d. Select region_0 from the Registers to Patch selection list.
e. Click Patch and close the Patch dialog box.
6. Request the saving of data files every 200 steps.
Solution → Activities → Autosave...
a. Enter 200 for Save Data File Every (Time Steps).
b. Ensure that time-step is selected from the Append File Name with drop-down list.
c. Enter inkjet for the File Name.
ANSYS Fluent will append the time step value to the file name prefix (inkjet). The standard
.dat.h5 extension will also be appended. This will yield file names of the form inkjet-100200.dat.h5, where 200 is the time step number.
d. Click OK to close the Autosave dialog box.
7. Save the initial case file (inkjet.cas.h5).
File → Write → Case...
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Setup and Solution
8. Run the calculation.
Solution → Run Calculation
a. Enter 1.0e-8 seconds for the Time Step Size (s).
Note:
Small time steps are required to capture the oscillation of the droplet interface and
the associated high velocities. Failure to use sufficiently small time steps may cause
differences in the results between platforms.
b. Enter 3000 for the Number of Time Steps.
c. Click Calculate.
The solution will run for 3000 iterations.
18.4.10. Postprocessing
1. Read the data file for the solution after 6 microseconds (inkjet-1-00600.dat.h5).
File → Read → Data...
2. Create and display a filled contour of water volume fraction after 6 microseconds (Figure 18.5: Contours of Water Volume Fraction After 6 μs (p. 753)).
Results → Graphics → Contours → New...
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Using the VOF Model
a. Change the Contour Name to contour-volume-fraction.
b. Enable Filled in the Options group box.
c. Select Phases... and Volume fraction from the Contours of drop-down lists.
d. Select water-liquid from the Phase drop-down list.
e. Click Save/Display.
Tip:
In order to display the contour plot in the graphics window, you may need to click the
Fit to Window button
.
3. Save the case file (inkjet.cas.h5).
File → Write → Case...
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Setup and Solution
4. Display contours of water volume fraction after 12, 18, 24, and 30 microseconds (Figure 18.6: Contours of Water Volume Fraction After 12 μs (p. 754) - Figure 18.9: Contours of Water Volume Fraction
After 30 μs (p. 755)).
a. Read the data file for the solution after 12 microseconds (inkjet-1-01200.dat.h5).
File → Read → Data...
b. Reload the contour graphic saved in the previous step.
Results → Graphics → Contours → contour-volume-fraction
Display
c. Repeat these steps for the 18, 24, and 30 microseconds files.
Figure 18.5: Contours of Water Volume Fraction After 6 μs
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Figure 18.6: Contours of Water Volume Fraction After 12 μs
Figure 18.7: Contours of Water Volume Fraction After 18 μs
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Summary
Figure 18.8: Contours of Water Volume Fraction After 24 μs
Figure 18.9: Contours of Water Volume Fraction After 30 μs
18.5. Summary
This tutorial demonstrated the application of the volume of fluid method with surface tension effects.
The problem involved the 2D axisymmetric modeling of a transient liquid-gas interface, and postprocessing showed how the position and shape of the surface between the two immiscible fluids changed
over time.
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Chapter 19: Modeling Cavitation
This tutorial is divided into the following sections:
19.1. Introduction
19.2. Prerequisites
19.3. Problem Description
19.4. Setup and Solution
19.5. Summary
19.1. Introduction
This tutorial examines the pressure-driven cavitating flow of water through a sharp-edged orifice. This
is a typical configuration in fuel injectors, and brings a challenge to the physics and numerics of cavitation models because of the high pressure differentials involved and the high ratio of liquid to vapor
density. Using the multiphase modeling capability of ANSYS Fluent, you will be able to predict the
strong cavitation near the orifice after flow separation at a sharp edge.
This tutorial demonstrates how to do the following:
• Set boundary conditions for internal flow.
• Use the mixture model with cavitation effects.
• Calculate a solution using the pressure-based coupled solver.
19.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
19.3. Problem Description
The problem considers the cavitation caused by the flow separation after a sharp-edged orifice. The
flow is pressure driven, with an inlet pressure of 5 x 105 Pa and an outlet pressure of 9.5 x 104 Pa. The
orifice diameter is 4 x 10–3 m, and the geometrical parameters of the orifice are D/d = 2.88 and L/d =
4, where D, d, and L are the inlet diameter, orifice diameter, and orifice length respectively. The geometry
of the orifice is shown in Figure 19.1: Problem Schematic (p. 758).
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Modeling Cavitation
Figure 19.1: Problem Schematic
19.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
19.4.1. Preparation
19.4.2. Reading and Checking the Mesh
19.4.3. Solver Settings
19.4.4. Models
19.4.5. Materials
19.4.6. Phases
19.4.7. Boundary Conditions
19.4.8. Operating Conditions
19.4.9. Solution
19.4.10. Postprocessing
19.4.1. Preparation
To prepare for running this tutorial:
1.
Download the cavitation.zip file here.
2.
Unzip cavitation.zip to your working directory.
The mesh file cav.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
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Setup and Solution
6.
Enable Double Precision under Options.
Note:
The double precision solver is recommended for modeling multiphase flows
simulation.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
19.4.2. Reading and Checking the Mesh
1. Read the mesh file cav.msh.
File → Read → Mesh...
2. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
3. Check the mesh scale.
Domain → Mesh → Scale...
a. Retain the default settings.
b. Close the Scale Mesh dialog box.
4. Examine the mesh (Figure 19.2: The Mesh in the Orifice (p. 760)).
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Modeling Cavitation
Figure 19.2: The Mesh in the Orifice
As seen in Figure 19.2: The Mesh in the Orifice (p. 760), half of the problem geometry is modeled, with
an axis boundary (consisting of two separate lines) at the centerline. The quadrilateral mesh is slightly
graded in the plenum to be finer toward the orifice. In the orifice, the mesh is uniform with aspect ratios
close to , as the flow is expected to exhibit two-dimensional gradients.
When you display data graphically in a later step, you will mirror the view across the centerline to
obtain a more realistic view of the model.
Since the bubbles are small and the flow is high speed, gravity effects can be neglected and the problem
can be reduced to axisymmetrical. If gravity could not be neglected and the direction of gravity were
not coincident with the geometrical axis of symmetry, you would have to solve a 3D problem.
19.4.3. Solver Settings
1. Specify an axisymmetric model.
Setup →
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Setup and Solution
a. Retain the default selection of Pressure-Based in the Type list.
The pressure-based solver must be used for multiphase calculations.
b. Select Axisymmetric in the 2D Space list.
Note:
A computationally intensive, transient calculation is necessary to accurately simulate
the irregular cyclic process of bubble formation, growth, filling by water jet re-entry,
and break-off. In this tutorial, you will perform a steady-state calculation to simulate
the presence of vapor in the separation region in the time-averaged flow.
19.4.4. Models
1. Enable the multiphase mixture model.
Physics → Models → Multiphase...
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a. Select Mixture in the Model list.
The Multiphase Model dialog box will expand.
b. Clear Slip Velocity in the Mixture Parameters group box.
In this flow, the high level of turbulence does not allow large bubble growth, so gravity is not important. It is also assumed that the bubbles have same velocity as the liquid. Therefore, there is no
need to solve for the slip velocity.
c. Click Apply and close the Multiphase Model dialog box.
Important:
When setting up your case, if you have made changes in the current tab, you should
click the Apply button to make them effective before moving to the next tab.
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Setup and Solution
Otherwise, the relevant models may not be available in the other tabs, and your
settings may be lost.
2. Enable the k-ω SST turbulence model.
Physics → Models → Viscous...
a. Retain the default selection of k-omega (2 eqn) in the Model list.
b. Retain the default selection of SST in the k-omega Model list
c. Click OK to close the Viscous Model dialog box.
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19.4.5. Materials
For the purposes of this tutorial, you will be modeling the liquid and vapor phases as incompressible.
Note that more comprehensive models are available for the densities of these phases, and could be
used to more fully capture the affects of the pressure changes in this problem.
1. Create a new material to be used for the primary phase.
Setup → Materials → Fluid
New...
a. Enter water for Name.
b. Enter 1000 kg/m3 for Density.
c. Enter 0.001 kg/m–s for Viscosity.
d. Click Change/Create and select Yes.
2. Copy water vapor from the materials database and modify the properties of your local copy.
a. In the Create/Edit Materials dialog box, click the Fluent Database... button to open the
Fluent Database Materials dialog box.
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Setup and Solution
i.
Select water-vapor (h2o) from the Fluent Fluid Materials selection list.
Scroll down the list to find water-vapor (h2o).
ii. Click Copy to include water vapor in your model.
water-vapor appears under Fluid in the Materials task page
iii. Close the Fluent Database Materials dialog box.
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b. Enter 0.02558 kg/m3 for Density.
c. Enter 1.26e-06 kg/m–s for Viscosity.
d. Click Change/Create and close the Create/Edit Materials dialog box.
19.4.6. Phases
Setup → Models → Multiphase
Edit...
In the Multiphase Model dialog box, go to the Phases tab.
1. Specify liquid water as the primary phase.
a. In the Phases selection list, select phase-1 – Primary Phase.
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Setup and Solution
b. Enter liquid for Name.
c. Select water from the Phase Material drop-down list.
d. Click Apply.
2. Specify water vapor as the secondary phase.
a. In the Phases selection list, select phase-2 – Secondary Phase.
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b. Enter vapor for Name.
c. Select water-vapor from the Phase Material drop-down list.
d. Click Apply.
3. Enable the cavitation model.
a. In the Multiphase Model dialog box, go to the Phase Interaction tab.
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Setup and Solution
b. In the Heat, Mass, Reaction tab, set Number of Mass Transfer Mechanisms to 1.
The dialog box expands to show relevant modeling parameters.
c. Ensure that liquid is selected from the From Phase drop-down list in the Mass Transfer group
box.
d. Select vapor from the To Phase drop-down list.
e. Select cavitation from the Mechanism drop-down list.
The Cavitation Model dialog box will open to show the cavitation inputs.
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i.
Retain the value of 3540 Pa for Vaporization Pressure.
The vaporization pressure is a property of the working liquid, which depends mainly on the
temperature and pressure. The default value is the vaporization pressure of water at 1 atmosphere and a temperature of 300 K.
ii. Retain the value of 1e+11 for Bubble Number Density.
iii. Click OK to close the Cavitation Model dialog box.
f.
Click Apply and close the Multiphase Model dialog box.
19.4.7. Boundary Conditions
For the multiphase mixture model, you will specify conditions for the mixture (that is, conditions that apply
to all phases) and the conditions that are specific to the primary and secondary phases. In this tutorial,
boundary conditions are required only for the mixture and secondary phase of two boundaries: the pressure
inlet (consisting of two boundary zones) and the pressure outlet. The pressure outlet is the downstream
boundary, opposite the pressure inlets.
Setup →
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Boundary Conditions
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Setup and Solution
1. Set the boundary conditions at inlet_1 for the mixture. Ensure that mixture is selected from the
Phase drop-down list in the Boundary Conditions task page.
Setup →
Boundary Conditions →
inlet_1 → Edit...
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a. Enter 500000 Pa for Gauge Total Pressure.
b. Enter 449000 Pa for Supersonic/Initial Gauge Pressure.
If you choose to initialize the solution based on the pressure-inlet conditions, the Supersonic/Initial
Gauge Pressure will be used in conjunction with the specified stagnation pressure (the Gauge
Total Pressure) to compute initial values according to the isentropic relations (for compressible
flow) or Bernoulli’s equation (for incompressible flow). Otherwise, in an incompressible flow calculation, ANSYS Fluent will ignore the Supersonic/Initial Gauge Pressure input.
c. Retain the default selection of Normal to Boundary from the Direction Specification Method
drop-down list.
d. Retain the default settings in the Turbulence group box.
e. Click Apply and close the Pressure Inlet dialog box.
2. Set the boundary conditions at inlet-1 for the secondary phase.
Setup →
Boundary Conditions →
inlet_1
a. Select vapor from the Phase drop-down list.
b. Click Edit... to open the Pressure Inlet dialog box.
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Setup and Solution
i.
In the Multiphase tab, retain the default value of 0 for Volume Fraction.
ii. Click Apply and close the Pressure Inlet dialog box.
3. Copy the boundary conditions defined for the first pressure inlet zone (inlet_1) to the second
pressure inlet zone (inlet_2).
Setup →
Boundary Conditions →
inlet_1
a. Select mixture from the Phase drop-down list.
b. Click Copy... to open the Copy Conditions dialog box.
i.
Select inlet_1 from the From Boundary Zone selection list.
ii. Select inlet_2 from the To Boundary Zones selection list.
iii. Click Copy.
A Question dialog box will open, asking if you want to copy inlet_1 boundary conditions to
inlet_2. Click OK.
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iv. Close the Copy Conditions dialog box.
4. Set the boundary conditions at outlet for the mixture.
Setup →
Boundary Conditions →
a. Enter 95000
outlet → Edit...
for Gauge Pressure.
b. Retain the default settings in the Turbulence group box.
c. Click Apply and close the Pressure Outlet dialog box.
5. Set the boundary conditions at outlet for the secondary phase.
Setup →
Boundary Conditions →
outlet
a. Select vapor from the Phase drop-down list.
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Setup and Solution
b. Click Edit... to open the Pressure Outlet dialog box.
i.
In the Multiphase tab, retain the default value of 0 for Backflow Volume Fraction.
ii. Click Apply and close the Pressure Outlet dialog box.
19.4.8. Operating Conditions
1. Set the operating pressure.
Setup →
Boundary Conditions → Operating Conditions...
a. Enter 0 Pa for Operating Pressure.
b. Click OK to close the Operating Conditions dialog box.
19.4.9. Solution
1. Set the solution parameters.
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Modeling Cavitation
Solution → Solution → Methods...
a. Select Coupled from the Scheme drop-down list in the Pressure-Velocity Coupling group
box.
b. Retain the selection of PRESTO! from the Pressure drop-down list in the Spatial Discretization
group box.
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Setup and Solution
c. Select QUICK for Momentum and Volume Fraction.
d. Retain First Order Upwind for Turbulent Kinetic Energy and Turbulent Dissipation Rate.
e. Enable Pseudo Transient.
f.
Enable High Order Term Relaxation.
The relaxation of high order terms will help to improve the solution behavior of flow simulations
when higher order spatial discretizations are used (higher than first).
2. Set the solution controls.
Solution → Controls → Controls...
a. Set the pseudo transient explicit relaxation factor for Volume Fraction to 0.3.
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3. Enable the plotting of residuals during the calculation.
Solution → Reports → Residuals...
a. Ensure that Plot is enabled in the Options group box.
b. Enter 1e-05 for the Absolute Criteria of continuity, x-velocity, y-velocity, k, omega, and
vf-vapor.
Decreasing the criteria for these residuals will improve the accuracy of the solution.
c. Click OK to close the Residual Monitors dialog box.
4. Initialize the solution.
Solution → Initialization
a. Select Hybrid from the Initialization group box.
b. Click More Settings... to open the Hybrid Initialization dialog box.
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Setup and Solution
c. Enable Use Specified Initial Pressure on Inlets in the Initialization Options group box. The
velocity will now be initialized to the Initial Gauge Pressure value that you set in the Pressure
Inlet boundary condition dialog box. For more information on initialization options, see hybrid
initialization in the Fluent User's Guide.
d. Click OK to close the Hybrid Initialization dialog box.
e. Click Initialize to initialize the solution.
Note:
For flows in complex topologies, hybrid initialization will provide better initial velocity
and pressure fields than standard initialization. This will help to improve the convergence behavior of the solver.
5. Save the case file (cav.cas.h5).
File → Write → Case...
6. Start the calculation by requesting 500 iterations.
Solution → Run Calculation → Run Calculation...
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a. Enter 500 for Number of Iterations.
b. Click Calculate.
7. Save the case and data files (cav.cas.h5 and cav.dat.h5).
File → Write → Case & Data...
19.4.10. Postprocessing
1. Create and plot a definition of pressure contours in the orifice (Figure 19.3: Contours of Static
Pressure (p. 782)).
Results → Graphics → Contours → New...
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a. Change Contour Name to contour-static-pressure
b. Enable Filled in the Options group box.
c. Enable Banded in the Coloring group box.
d. Retain the default selection of Pressure... and Static Pressure from the Contours of dropdown lists.
e. Click Save/Display and close the Contours dialog box.
The contour-static-pressure contour definition appears under the Results/Graphics/Contours tree branch. Once you create a plot definition, you can use a right-click menu
to display this definition at a later time, for instance, in subsequent simulations with different
settings ;or in combination with other plot definitions.
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Figure 19.3: Contours of Static Pressure
Note the dramatic pressure drop at the flow restriction in Figure 19.3: Contours of Static Pressure (p. 782).
Low static pressure is the major factor causing cavitation. Additionally, turbulence contributes to
cavitation due to the effect of pressure fluctuation (Figure 19.4: Mirrored View of Contours of Static
Pressure (p. 783)) and turbulent diffusion (Figure 19.5: Contours of Turbulent Kinetic Energy (p. 784)).
2. Mirror the display across the centerline (Figure 19.4: Mirrored View of Contours of Static Pressure (p. 783)).
View → Display → Views...
Mirroring the display across the centerline gives a more realistic view.
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a. Select symm_2 and symm_1 from the Mirror Planes selection list.
b. Click Apply and close the Views dialog box.
Figure 19.4: Mirrored View of Contours of Static Pressure
3. Create and plot a contour definition of the turbulent kinetic energy (Figure 19.5: Contours of Turbulent Kinetic Energy (p. 784)).
Results → Graphics → Contours → New...
a. Change Contour Name to contour-tke
b. Enable Filled in the Options group box.
c. Enable Banded in the Coloring group box.
d. Select Turbulence... and Turbulent Kinetic Energy(k) from the Contours of drop-down lists.
e. Click Save/Display.
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Figure 19.5: Contours of Turbulent Kinetic Energy
In this example, the mesh used is fairly coarse. However, in cavitating flows the pressure distribution
is the dominant factor, and is not very sensitive to mesh size.
4. Create and plot a contour definition of the volume fraction of water vapor (Figure 19.6: Contours
of Vapor Volume Fraction (p. 785)).
Results → Graphics → Contours → New...
a. Change Contour Name to contour-vf-vapor
b. Enable Filled in the Options group box.
c. Enable Banded in the Coloring group box.
d. Select Phases... and Volume fraction from the Contours of drop-down lists.
e. Select vapor from the Phase drop-down list.
f.
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Summary
Figure 19.6: Contours of Vapor Volume Fraction
The high turbulent kinetic energy region near the neck of the orifice in Figure 19.5: Contours of Turbulent
Kinetic Energy (p. 784) coincides with the highest volume fraction of vapor in Figure 19.6: Contours of
Vapor Volume Fraction (p. 785). This indicates the correct prediction of a localized high phase change
rate. The vapor then gets convected downstream by the main flow.
5. Save the case file (cav.cas.h5).
File → Write → Case...
19.5. Summary
This tutorial demonstrated how to set up and resolve a strongly cavitating pressure-driven flow through
an orifice, using multiphase mixture model of ANSYS Fluent with cavitation effects. You learned how
to set the boundary conditions for an internal flow. A steady-state solution was calculated to simulate
the formation of vapor in the neck of the flow after the section restriction at the orifice. A more computationally intensive transient calculation is necessary to accurately simulate the irregular cyclic process
of bubble formation, growth, filling by water jet re-entry, and break-off.
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Chapter 20: Using the Eulerian Multiphase Model
This tutorial is divided into the following sections:
20.1. Introduction
20.2. Prerequisites
20.3. Problem Description
20.4. Setup and Solution
20.5. Summary
20.1. Introduction
This tutorial examines a turbulent two-phase flow consisting of air sparged into a water-filled mixing
lab reactor. You will use the Eulerian multiphase model to simulate the mixing tank processes since the
air and water phases are not in equilibrium throughout the simulation.
This tutorial demonstrates how to do the following:
• Set up a multiphase flow simulation involving air and water.
• Use multiple frames of reference.
• Use a degassing outlet boundary condition to enable only air, but not water, to escape from the
boundary.
• Calculate a solution using the multiphase coupled solver with the Eulerian model.
• Display the solution results.
• Calculate torque and power requirements.
20.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
20.3. Problem Description
The problem to be modeled in this tutorial is shown schematically in Figure 20.1: Problem Schematic (p. 788).
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Figure 20.1: Problem Schematic
The geometry consists of a mixing vessel, four baffles along the vessel wall, a ring sparger, a pitch blade
turbine, a Rushton blade turbine, and a rotating vertical shaft. There is no water flow into or out of the
vessel. Air is injected into the tank at the bottom through the ring sparger at a speed of 0.05 m/s. Small
inlet holes in the sparger ring are ignored, and the air inlet is modeled as a uniform circular strip. The
air mixes with water, producing small bubbles. The Rushton blade turbine agitates the air-water mixture,
evenly distributing the air bubbles. The pitch blade turbine performs dispersion and pumping operations.
Both impellers rotate at 450 rpm in the counterclockwise direction about the Z axis (as viewed from
the top). Dispersed gas bubbles can escape through the top water surface, which is open to the ambient
air. This model can be used as a reasonable representation of the initial conditions in a real mixing tank.
20.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
20.4.1. Preparation
20.4.2. Mesh
20.4.3. Solver Settings
20.4.4. Models
20.4.5. Materials
20.4.6. Phases
20.4.7. Cell Zone Conditions
20.4.8. Boundary Conditions
20.4.9. Solution
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Setup and Solution
20.4.10. Postprocessing
20.4.1. Preparation
To prepare for running this tutorial:
1.
Download the mixing_tank.zip file here.
2.
Unzip mixing_tank.zip to your working directory.
The mesh file mixing_tank.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 4 under Parallel (Local Machine).
20.4.2. Mesh
1. Read the mesh file mixing_tank.msh.
File → Read → Mesh...
As Fluent reads the mesh file, it will report the progress in the console.
A warning message will be displayed that the degassing boundary condition type is not compatible
with currently enabled models. You will resolve this issue when you enable the Eulerian multiphase
model in a subsequent step.
Click OK and close the Information dialog box.
2. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
Fluent will perform various checks on the mesh and will report the progress in the console. Make sure
that the reported minimum volume is a positive number.
3. Display the mesh.
Domain → Mesh → Display...
a. In the Options group box, enable Faces and Edges.
b. In the Surfaces selection list, select wall_liquid_level, gas-inlet, and Wall (to select all walls),
deselect fluid-tank_body
c. Click Display and close the Mesh Display dialog box.
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4. Examine the mesh (Figure 20.2: Mesh Display of the Mixing Tank (p. 790)).
Extra:
You can use the right mouse button to check which zone number corresponds to each
boundary. If you click the right mouse button on one of the boundaries in the graphics
window, its zone number, name, and type will be printed in the ANSYS Fluent console.
This feature is especially useful when you have several zones of the same type and you
want to distinguish between them quickly.
Figure 20.2: Mesh Display of the Mixing Tank
20.4.3. Solver Settings
Related video that demonstrates steps for setting up, solving, and postprocessing the solution results
for a two-phase turbulent flow within a mixing tank:
1. Retain the default Solver settings.
Physics → Solver → General...
2. Set the gravitational acceleration.
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Setup and Solution
Physics → Solver → Operating Conditions...
a. In the Operating Conditions dialog box, enable Gravity to account for gravitational forces.
b. In the Gravitational Acceleration group box, enter -9.81 m/s2 for the Gravitational Acceleration in the Z direction.
c. Select Specified Operating Density.
d. Retain the default value of 1.225 kg/m3 for Operating Density.
For this simulation, you will model air as an incompressible fluid with a density of 1.225 kg/m3,
which is a default value.
Note:
For multiphase flows, the operating density should be set to the density of the least
dense phase.
e. Click OK to close the Operating Conditions dialog box.
f.
Click OK to close the Information dialog box.
20.4.4. Models
1. Enable the Eulerian multiphase model.
Since you will use the default settings for the Eulerian model, you can enable it directly from the tree
by right-clicking the Multiphase node and choosing Eulerian from the context menu.
Setup → Models → Multiphase
Eulerian
Click OK to close the Information dialog box.
Enabling the Eulerian multiphase model will also automatically enable the operating density parameters.
You can verify this in the Operating Conditions dialog box.
2. Verify the operating density.
Physics → Solver → Operating Conditions...
a. Ensure that minimum-phase-averaged is selected from the Operating Density Method
drop-down list.
b. Click OK to close the Operating Conditions dialog box.
3. Enable the k-ω turbulence model with standard wall functions.
Physics → Models → Viscous...
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a. Retain the default k-omega model in the Model group box.
b. Retain SST in the k-omega Model group box.
c. In the Turbulence Multiphase Model group box, select Dispersed.
The dispersed turbulence model is suitable for cases when the dispersed phase is dilute. The model
assumes that turbulence in the primary phase is dominant, while the turbulent quantities of the
secondary phase can be obtained from the mean characteristics of the primary phase.
d. Click OK to close the Viscous Model dialog box.
20.4.5. Materials
The default properties for water defined in ANSYS Fluent are suitable for this problem. In this step, you will
make sure that this material is available for selecting in future steps.
1. Add water to the list of fluid materials by copying it from the ANSYS Fluent materials database.
Setup →
Materials →
Fluid → air → Create/Edit...
a. Click Fluent Database... in the Create/Edit Materials dialog box to open the Fluent Database
Materials dialog box.
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Setup and Solution
i.
Select water-liquid (h2o<l>) in the Fluent Fluid Materials selection list.
Scroll down the list to find water-liquid (h2o<l>). Selecting this item will display the default
properties in the dialog box.
ii. Click Copy and close the Fluent Database Materials dialog box.
The Create/Edit Materials dialog box will now display the copied properties for water-liquid.
b. Click Change/Create and close the Create/Edit Materials dialog box.
20.4.6. Phases
In the following steps you will define the liquid water and air phases that flow in the mixing tank.
Setup → Models → Multiphase
Edit...
1. In the Phases tab of the Multiphase Model dialog box, specify liquid water as the primary phase.
a. In the Phases selection list, select phase-1 – Primary Phase.
b. Enter water for Name.
c. Select water-liquid from the Phase Material drop-down list.
d. Click Apply.
2. Specify air as the secondary phase.
a. In the Phases selection list, select phase-2 – Secondary Phase.
b. Enter air for Name.
c. Retain the default selection of air from the Phase Material drop-down list.
d. Enter 0.0015 m for Diameter.
The diameter of the air bubbles that are formed when the air is injected into the tank depends on
the diameter of the inlet holes in the real reactor, which is 1 mm in this example.
e. Click Apply.
3. Define the interphase interactions formulations to be used.
a. Open the Phase Interaction tab.
b. In the Forces tab, select grace from the Coefficient drop-down list (Drag Coefficient group
box).
The Grace model is suitable for liquid-gas mixtures with low gas density and bubble sizes of 12 mm.
Click OK to close the Grace Swarm Correction dialog box.
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c. For Surface Tension Coefficients (Force Setup group box), select constant from the dropdown list and enter 0.073.
d. Click Apply and close the Multiphase Model dialog box.
20.4.7. Cell Zone Conditions
The mesh has three fluid cell zones: fluid_mrf_1-1 and fluid_mrf_2-0 are zones associated with the Rushton
blade turbine and pitch blade turbine, respectively, and fluid_tank-2 represents the rest of the tank. In this
section, you will use multiple reference frames to define boundary conditions for the cell zones that contain
rotating components. Moving reference frames enable you to model the flow around rotating parts as
steady-state with respect to the moving frames.
Physics → Zones → Cell Zones...
Tip:
To visually confirm the location of a cell or boundary zone, you can display it by rightclicking it in the tree and selecting either Display or Add to Graphics. Conversely, if you
click a cell or boundary mesh in the graphics window, the selected item will be highlighted
in the tree. You can use Ctrl or Shift to select multiple zones.
1. Set up the cell zone conditions for the fluid zone associated with the Rushton blade turbine (fluid_mrf_1-1).
Setup → Cell Zone Conditions → Fluid → fluid_mrf_1-1
Edit...
a. In the Fluid dialog box, enter rbt-zone for Zone Name.
This name is more descriptive for the zone than fluid_mrf_1-1.
b. Select Frame Motion.
c. Retain the default values of (0, 0, 1) for X, Y, and Z in the Rotation-Axis Direction group box.
d. Enter 450 rpm for Speed in the Rotational Velocity group box.
e. Click Apply and close the Fluid dialog box.
2. In a similar manner, set up the cell zone conditions for the fluid zone associated with the pitch
blade turbine (fluid_mrf_2-0).
Setup → Cell Zone Conditions → fluid_mrf_2-0
Edit...
a. In the Fluid dialog box, enter pbt-zone for Zone Name.
b. Select Frame Motion.
c. Retain the default values of (0, 0, 1) for X, Y, and Z in the Rotation-Axis Direction group box.
d. Enter 450 rpm for Speed in the Rotational Velocity group box.
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Setup and Solution
e. Click Apply and close the Fluid dialog box.
3. Retain the default settings for fluid_tank-2, which is stationary in the absolute reference frame.
20.4.8. Boundary Conditions
You will now define the conditions on the boundaries of the domain. Since each wall uses the same reference
frame as the cell zone within which they are located, all walls will use the default stationary wall condition.
A stationary wall condition implies that the wall is stationary with respect to the adjacent cell zone.
Therefore, in the case of a rotating reference frame, a stationary wall is actually rotating with respect to
the absolute reference frame.
The degassing boundary condition at the top of the fluid was created in a meshing application. At the
degassing outlet, only gas phase can leave the domain. The degassing boundary condition became active
after you enabled the Eulerian multiphase model in Fluent. No input is required for this type of boundary
condition. For this problem, you only need to set the boundary conditions for the velocity inlet. Since this
is a multiphase model, you will set the conditions that are specific to the primary and secondary phases.
1. Set the boundary conditions at the inlet (gas-inlet) for the primary phase (water).
Setup → Boundary Conditions → Inlet → gas-inlet → water
Edit...
Since this is a dispersed turbulent flow, only turbulence must be defined for the water phase.
a. In the Turbulence group box, select Intensity and Hydraulic Diameter as the turbulence
Specification Method.
b. Enter 3% for Turbulent Intensity.
c. Enter 0.0254 m for Hydraulic Diameter.
d. Click Apply and close the Velocity Inlet dialog box.
2. Set the boundary conditions at the inlet (gas-inlet) for the secondary phase (air).
Setup → Boundary Conditions → Inlet → gas-inlet → air
Edit...
a. Enter 0.05 m/s for Velocity Magnitude.
b. In the Multiphase tab, enter 1 for Volume Fraction.
A value of unity implies that only air enters the inlet.
c. Click Apply and close the Velocity Inlet dialog box.
20.4.9. Solution
1. Specify the discretization schemes.
Solution → Solution → Methods...
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In the Solution Methods task page, configure the following settings.
Group Box
Setting
Value
Pressure Velocity Coupling
Scheme
Coupled
N/A
Pseudo-Transient
(Selected)
N/A
Warped-Face Gradient Correction
(Selected)
2. Ensure that the plotting of residuals is enabled during the calculation.
Solution → Reports → Residuals...
3. Initialize the solution.
Solution → Initialization → Initialize
4. Save the case file (mixing_tank.cas.h5).
File → Write → Case...
5. Start calculation.
Solution → Run Calculation → Run Calculation...
a. Enter 1500 for Number of Iterations.
b. Retain the default selection of Automatic for the Time Step Method.
c. Retain the default value of 1 for Timescale Factor.
Note:
It may take significant time and computer resources to complete the problem calculation.
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Setup and Solution
Figure 20.3: Residual History
6. After the solution has converged, save the case and data files (mixing_tank.cas.h5 and
mixing_tank.dat.h5).
File → Write → Case & Data...
20.4.10. Postprocessing
1. Display the distribution of air on the XZ plane (Figure 20.4: Contours of Air Volume Fraction on
the XZ plane (p. 799)).
Results → Graphics → Contours → New...
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a. Enter contour-air-vf-xz for Contour Name.
b. From the Contours of drop-down lists, select Phases... and Volume Fraction.
c. From the Phase drop-down lists, select air.
d. In the Surfaces selection list, deselect all surfaces by clicking
wall_impeller_1, and wall_impeller_2.
and then select y=0,
e. In the Options group box, make sure that Filled is selected.
f.
Disable Global Range, Auto Range, and Clip to Range.
g. Enter 0.01 for Max.
The specified range will allow you to better view the volume fraction variation.
h. Select Draw Mesh to open the Mesh Display dialog box.
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Setup and Solution
i.
In the Mesh Display dialog box, click
next to the Surfaces filter to deselect all surfaces
and then select wall_baffle_1, wall_sparger, and all walls whose names begin with
'wall_shaft'.
ii. Enable Edges and disable Faces in the Options group box.
iii. Click Close to close the Mesh Display dialog box.
i.
Ensure that Smooth is selected in the Coloring group box.
j.
Click Save/Display and use the interactive triad to orient the view as shown in Figure 20.4: Contours of Air Volume Fraction on the XZ plane (p. 799).
Note:
You may need to deselect Headlight and Lighting in the View ribbon tab (Display
group).
Figure 20.4: Contours of Air Volume Fraction on the XZ plane
The contour map of the air volume fraction on the XZ plane shows how the air is agitated by impellers as it moves upward in the mixing tank. The shape of the Rushton blade turbine is forming
cavities below the turbine.
2. Display the distribution of air on the plane z=0.08 (Figure 20.5: Contours of Air Volume Fraction
on the z=0.08 plane (p. 800)).
Results → Graphics → Contours → New...
a. Enter contour-air-vf-z=0.08 for Contour Name.
b. Set up the contour plot in a similar manner to step 1, except using the z=0.08 instead of y=0.
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c. Click Save/Display and close the Contours dialog box.
d. In the View Tools toolbar, from the Set View drop-down list (
), select the view from the
negative Z axis (
) to obtain the view shown in Figure 20.5: Contours of Air Volume Fraction
on the z=0.08 plane (p. 800).
Figure 20.5: Contours of Air Volume Fraction on the z=0.08 plane
Note that the air is collecting on the bottom surface of the Rushton blade turbine disk before its
dispersed by the impeller’s blades.
3. Display vectors of velocity magnitude for water on the XZ plane (Figure 20.6: Vectors of Water
Velocity Magnitude on the XZ plane (p. 801)).
Results → Graphics → Vectors → New...
a. Enter vector-vel-water for Vector Name.
b. Enable Draw Mesh and retain the default settings.
c. Select arrow from the Style drop-down list.
d. Select Velocity from the Vectors of drop-down list.
e. Select water from the Phase drop-down list.
Since the Eulerian model solves individual momentum equations for each phase, you can choose
the phase for which solution data is plotted.
f.
From the Color by drop-down lists, select Velocity... and Velocity Magnitude.
g. Retain the selection of water from the Phase drop-down list.
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h. In the Surfaces selection list, deselect all surfaces by clicking
wall_impeller_1, and wall_impeller_2.
i.
and then select y=0,
Click Save/Display, close the Vectors dialog box, and use the interactive triad to orient the
view as shown in Figure 20.6: Vectors of Water Velocity Magnitude on the XZ plane (p. 801).
Figure 20.6: Vectors of Water Velocity Magnitude on the XZ plane
The vector plot of the water velocity shows that the water moves in a circular motion, creating a
closed loop since it cannot escape the reactor.
4. Display vectors of velocity magnitude for air on the XZ plane (Figure 20.7: Vectors of Air Velocity
Magnitude on the XZ plane (p. 802)).
Results → Graphics → Vectors → New...
a. Enter vector-vel-air for Vector Name.
b. Enable Draw Mesh and retain the default settings.
c. Select arrow from the Style drop-down list.
d. Under Vectors of, select air from the Phase drop-down list.
e. Under Color by, select air from the Phase drop-down list.
f.
In the Surfaces selection list, deselect all surfaces by clicking
wall_impeller_1, and wall_impeller_2.
and then select y=0,
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g. Click Save/Display and close the Vectors dialog box.
Figure 20.7: Vectors of Air Velocity Magnitude on the XZ plane
The vector plot of the air velocity shows that the air moves upward all the way to the water surface,
where it escapes. The baffle walls located on the sides of the tank prevent the undesirable vortex
formation.
5. Calculate the torque about the shaft for the Rushton blade turbine.
Results → Reports → Forces...
a. From the Options group box, select Moments.
b. In the Moment Center group box, enter 0, 0, and 0 for X, Y, Z, respectively.
c. In the Moment Axis group box, enter 0, 0, and -1 for X, Y, Z, respectively.
d. From the Wall Zones selection list, deselect all zones by clicking
wall_impeller_1.
and then select
e. Click Print and close the Force Reports dialog box.
Fluent reports the individual and net values of the pressure moment, viscous moment, total
moment, pressure coefficient, viscous coefficient, and total coefficient about the specified
center in the console.
The power requirement is simply the required torque (0.03767 N m) multiplied by the rotational
speed (450 rpm = 47.12 rad/s): 0.03767 N m * 47.1 rad/s = 1.77 W.
802
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Summary
Note that this value does not account for any mechanical losses, motor efficiencies, and so
on.
6. Save the case file (mixing_tank.cas.h5).
File → Write → Case...
20.5. Summary
This tutorial demonstrated how to set up and solve a turbulent multiphase flow in the mixing tank using
the Eulerian multiphase model. You learned how to set degassing boundary conditions and boundary
conditions for primary and secondary phases. After completing the simulation, you displayed the results
of your calculation and calculated the torque and power requirements. For more information about the
Eulerian multiphase model, see the Fluent User's Guide.
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803
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Chapter 21: Modeling Solidification
This tutorial is divided into the following sections:
21.1. Introduction
21.2. Prerequisites
21.3. Problem Description
21.4. Setup and Solution
21.5. Summary
21.1. Introduction
This tutorial illustrates how to set up and solve a problem involving solidification and will demonstrate
how to do the following:
• Define a solidification problem.
• Define pull velocities for simulation of continuous casting.
• Define a surface tension gradient for Marangoni convection.
• Solve a solidification problem.
21.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
21.3. Problem Description
This tutorial demonstrates the setup and solution procedure for a fluid flow and heat transfer problem
involving solidification, namely the Czochralski growth process. The geometry considered is a 2D
axisymmetric bowl (shown in Figure 21.1: Solidification in Czochralski Model (p. 806)), containing liquid
metal. The bottom and sides of the bowl are heated above the liquidus temperature, as is the free
surface of the liquid. The liquid is solidified by heat loss from the crystal and the solid is pulled out of
the domain at a rate of 0.001
and a temperature of 500 . There is a steady injection of liquid at
the bottom of the bowl with a velocity of
and a temperature of 1300
properties are listed in Figure 21.1: Solidification in Czochralski Model (p. 806).
. Material
Starting with an existing 2D mesh, the details regarding the setup and solution procedure for the solidification problem are presented. The steady conduction solution for this problem is computed as an
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Modeling Solidification
initial condition. Then, the fluid flow is enabled to investigate the effect of natural and Marangoni
convection in a transient fashion.
Figure 21.1: Solidification in Czochralski Model
In the above figure,
is the mushy zone constant.
21.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
21.4.1. Preparation
21.4.2. Reading and Checking the Mesh
21.4.3. Specifying Solver and Analysis Type
21.4.4. Specifying the Models
21.4.5. Defining Materials
21.4.6. Setting the Cell Zone Conditions
21.4.7. Setting the Boundary Conditions
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Setup and Solution
21.4.8. Solution: Steady Conduction
21.4.9. Solution: Transient Flow and Heat Transfer
21.4.1. Preparation
To prepare for running this tutorial:
1.
Download the solidification.zip file here.
2.
Unzip solidification.zip to your working directory.
The mesh file solid.msh can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
6.
Disable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
21.4.2. Reading and Checking the Mesh
1. Read the mesh file solid.msh.
File → Read → Mesh...
As the mesh is read by ANSYS Fluent, messages will appear in the console reporting the progress of
the reading.
A warning about the use of axis boundary conditions is displayed in the console. You are asked to
consider making changes to the zone type or change the problem definition to axisymmetric. You will
change the problem to axisymmetric swirl later in this tutorial.
2. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and will report the progress in the console. Make
sure that the minimum volume is a positive number.
3. Examine the mesh (Figure 21.2: Mesh Display (p. 808)).
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Modeling Solidification
Figure 21.2: Mesh Display
21.4.3. Specifying Solver and Analysis Type
1. Select Axisymmetric Swirl from the 2D Space list.
Setup →
808
General
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Setup and Solution
The geometry comprises an axisymmetric bowl. Furthermore, swirling flows are considered in this
problem, so the selection of Axisymmetric Swirl best defines this geometry.
Also, note that the rotation axis is the X axis. Hence, the X direction is the axial direction and the Y
direction is the radial direction. When modeling axisymmetric swirl, the swirl direction is the tangential
direction.
2. Add the effect of gravity on the model.
Setup →
General →
Gravity
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Modeling Solidification
a. Enable Gravity.
b. Enter -9.81
for X in the Gravitational Acceleration group box.
21.4.4. Specifying the Models
1. Enable the laminar viscous model.
Setup → Models → Viscous
Edit...
a. Select Laminar in the Model group box.
2. Define the solidification model.
Setup → Models → Solidification & Melting
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Edit...
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Setup and Solution
a. Enable the Solidification/Melting option in the Solidification and Melting dialog box.
The Solidification and Melting dialog box will expand to show the related parameters.
b. Retain the default value of 100000 for the Mushy Zone Constant.
This default value is acceptable for most cases.
c. Enable the Include Pull Velocities option.
By including the pull velocities, you will account for the movement of the solidified material as it
is continuously withdrawn from the domain in the continuous casting process.
When you enable this option, the Solidification and Melting dialog box will expand to show the
Compute Pull Velocities option. If you were to enable this additional option, ANSYS Fluent would
compute the pull velocities during the calculation. This approach is computationally expensive and
is recommended only if the pull velocities are strongly dependent on the location of the liquid-solid
interface. In this tutorial, you will patch values for the pull velocities instead of having ANSYS Fluent compute them.
For more information about computing the pull velocities, see the Fluent User's Guide.
d. Click OK to close the Solidification and Melting dialog box.
An Information dialog box opens, telling you that available material properties have changed for
the solidification model. You will set the material properties later, so you can click OK in the dialog
box to acknowledge this information.
Note:
ANSYS Fluent will automatically enable the energy calculation when you enable the
solidification model, so you need not visit the Energy dialog box.
21.4.5. Defining Materials
In this step, you will create a new material and specify its properties, including the melting heat, solidus
temperature, and liquidus temperature.
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Modeling Solidification
1. Define a new material.
Setup → Materials → Fluid → air
Edit...
a. Enter liquid-metal for Name.
b. Select polynomial from the Density drop-down list in the Properties group box.
c. Configure the following settings In the Polynomial Profile dialog box:
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Setup and Solution
i.
Set Coefficients to 2.
ii. In the Coefficients group box, enter 8000 for 1 and -0.1 for 2.
As shown in Figure 21.1: Solidification in Czochralski Model (p. 806), the density of the material
is defined by a polynomial function:
.
iii. Click OK to close the Polynomial Profile dialog box.
d. In the Question dialog box, click Yes to overwrite air and add the new material (liquid-metal)
to the Fluent Fluid Materials drop-down list.
e. Set the liquid-metal material properties as follows:
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Modeling Solidification
f.
Enter 680
for Cp (Specific Heat).
g. Enter 30
for Thermal Conductivity.
h. Enter 0.00553
i.
Enter 100000
for Viscosity.
for Pure Solvent Melting Heat.
Scroll down the group box to find Pure Solvent Melting Heat and the properties that follow.
j.
Enter 1150
k. Enter 1150
l.
814
for Solidus Temperature.
for Liquidus Temperature.
Click Change/Create and close the Create/Edit Materials dialog box.
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Setup and Solution
21.4.6. Setting the Cell Zone Conditions
1. Set the cell zone conditions for the fluid (fluid).
Setup → Cell Zone Conditions → Fluid → fluid
Edit...
a. Ensure liquid-metal is selected from the Material Name drop-down list.
b. Click Apply and close the Fluid dialog box.
21.4.7. Setting the Boundary Conditions
1. Set the boundary conditions for the inlet (inlet).
Setup → Boundary Conditions → Inlet → inlet
Edit...
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Modeling Solidification
a. Enter 0.00101
for Velocity Magnitude.
b. Click the Thermal tab and enter 1300
816
for Temperature.
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Setup and Solution
c. Click Apply and close the Velocity Inlet dialog box.
2. Set the boundary conditions for the outlet (outlet).
Setup → Boundary Conditions → Inlet → outlet
Edit...
Here, the solid is pulled out with a specified velocity, so a velocity inlet boundary condition is used with
a positive axial velocity component.
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Modeling Solidification
a. From the Velocity Specification Method drop-down list, select Components.
The Velocity Inlet dialog box will change to show related inputs.
b. Enter 0.001
c. Enter 1
for Axial-Velocity.
for Swirl Angular Velocity.
d. Click the Thermal tab and enter 500
for Temperature.
e. Click Apply and close the Velocity Inlet dialog box.
3. Set the boundary conditions for the bottom wall (bottom-wall).
Setup → Boundary Conditions → Wall → bottom-wall
Edit...
a. Click the Thermal tab.
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Setup and Solution
i.
Select Temperature in the Thermal Conditions group box.
ii. Enter 1300
for Temperature.
b. Click Apply and close the Wall dialog box.
4. Set the boundary conditions for the free surface (free-surface).
Setup → Boundary Conditions → Wall → free-surface
Edit...
The specified shear and Marangoni stress boundary conditions are useful in modeling situations in
which the shear stress (rather than the motion of the fluid) is known. A free surface condition is an
example of such a situation. In this case, the convection is driven by the Marangoni stress and the
shear stress is dependent on the surface tension, which is a function of temperature.
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Modeling Solidification
a. Select Marangoni Stress in the Shear Condition group box.
The Marangoni Stress condition allows you to specify the gradient of the surface tension with
respect to temperature at a wall boundary.
b. Enter -0.00036
for Surface Tension Gradient.
c. Click the Thermal tab to specify the thermal conditions.
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Setup and Solution
i.
Select Convection from the Thermal Conditions group box.
ii. Enter 100
iii. Enter 1500
for Heat Transfer Coefficient.
for Free Stream Temperature.
d. Click Apply and close the Wall dialog box.
5. Set the boundary conditions for the side wall (side-wall).
Setup → Boundary Conditions → Wall → side-wall
Edit...
a. Click the Thermal tab.
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Modeling Solidification
i.
Select Temperature from the Thermal Conditions group box.
ii. Enter 1400
for the Temperature.
b. Click Apply and close the Wall dialog box.
6. Set the boundary conditions for the solid wall (solid-wall).
Setup → Boundary Conditions → Wall → solid-wall
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Edit...
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Setup and Solution
a. From the Wall Motion group box, select Moving Wall.
The Wall dialog box is expanded to show additional parameters.
b. in the Motion group box, in the lower box, select Rotational.
The Wall dialog box is changed to show the rotational speed.
c. Enter 1.0
for Speed.
d. Click the Thermal tab to specify the thermal conditions.
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Modeling Solidification
i.
Select Temperature from the Thermal Conditions selection list.
ii. Enter 500
for Temperature.
e. Click Apply and close the Wall dialog box.
21.4.8. Solution: Steady Conduction
In this step, you will specify the discretization schemes to be used and temporarily disable the calculation
of the flow and swirl velocity equations, so that only conduction is calculated. This steady-state solution
will be used as the initial condition for the time-dependent fluid flow and heat transfer calculation.
1. Set the solution parameters.
Solution → Solution → Methods...
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Setup and Solution
a. Select Coupled from the Scheme drop-down list in the Pressure-Velocity Coupling group
box.
b. Select PRESTO! from the Pressure drop-down list in the Spatial Discretization group box.
The PRESTO! scheme is well suited for rotating flows with steep pressure gradients.
c. Retain the default selection of Second Order Upwind from the Momentum, Swirl Velocity,
and Energy drop-down lists.
d. Enable Pseudo Transient.
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Modeling Solidification
The Pseudo Transient option enables the pseudo transient algorithm in the coupled pressure-based
solver. This algorithm effectively adds an unsteady term to the solution equations in order to improve
stability and convergence behavior. Use of this option is recommended for general fluid flow
problems.
2. Enable the calculation for energy.
Solution → Controls → Equations...
a. Deselect Flow and Swirl Velocity from the Equations selection list to disable the calculation
of flow and swirl velocity equations.
b. Click OK to close the Equations dialog box.
3. Confirm the Relaxation Factors.
Solution → Controls → Controls...
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Setup and Solution
Retain the default values.
4. Enable the plotting of residuals during the calculation.
Solution → Reports → Residuals...
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Modeling Solidification
a. Ensure Plot is enabled in the Options group box.
b. Click OK to accept the remaining default settings and close the Residual Monitors dialog box.
5. Initialize the solution.
Solution → Initialization
a. Retain the Method at the default of Hybrid in the Initialization group.
For flows in complex topologies, hybrid initialization will provide better initial velocity and pressure
field than standard initialization. This in general will help in improving the convergence behavior
of the solver.
b. Click Initialize.
6. Define a custom field function for the swirl pull velocity.
Parameters & Customization → Parameters → Custom Field Functions
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New...
Setup and Solution
In this step, you will define a field function to be used to patch a variable value for the swirl pull velocity
in the next step. The swirl pull velocity is equal to
, where is the angular velocity, and is the
radial coordinate. Since = 1 rad/s, you can simplify the equation to simply . In this example, the
value of is included for demonstration purposes.
a. From the Field Functions drop-down lists, select Mesh... and Radial Coordinate.
b. Click the Select button to add radial-coordinate in the Definition field.
If you make a mistake, click the DEL button on the calculator pad to delete the last item you added
to the function definition.
c. Click the
button on the calculator pad.
d. Click the 1 button.
e. Enter omegar for New Function Name.
f.
Click Define.
The omegar item appears under the Parameters & Customization/Parameters tree branch.
Note:
To check the function definition or delete the custom field function, click Manage....
Then in the Field Function Definitions dialog box, from the Field Functions selection list, select omegar to view the function definition.
g. Close the Custom Field Function Calculator dialog box.
7. Patch the pull velocities.
Solution → Initialization → Patch...
As noted earlier, you will patch values for the pull velocities, rather than having ANSYS Fluent compute
them. Since the radial pull velocity is zero, you will patch just the axial and swirl pull velocities.
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Modeling Solidification
a. From the Variable selection list, select Axial Pull Velocity.
b. Enter 0.001
for Value.
c. From the Zones to Patch selection list, select fluid.
d. Click Patch.
You have just patched the axial pull velocity. Next you will patch the swirl pull velocity.
e. From the Variable selection list, select Swirl Pull Velocity.
Scroll down the list to find Swirl Pull Velocity.
f.
Enable the Use Field Function option.
g. Select omegar from the Field Function selection list.
h. Ensure that fluid is selected from the Zones to Patch selection list.
i.
Click Patch and close the Patch dialog box.
8. Save the initial case and data files (solid0.cas.h5 and solid0.dat.h5).
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Setup and Solution
File → Write → Case & Data...
9. Start the calculation by requesting 20 iterations.
Solution → Run Calculation → Run Calculation...
a. In the Run Calculation task page, select User Specified for the Time Step Method in both
the Fluid Time Scale and the Solid Time Scale group boxes.
b. Retain the default values of 1 s and 1000 s for the Pseudo Time Step Size in the Fluid Time
Scale and the Solid Time Scale group boxes, respectively.
c. Enter 20 for Number of Iterations.
d. Click Calculate.
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Modeling Solidification
10. Create and display the definition of filled temperature contours (Figure 21.3: Contours of Temperature for the Steady Conduction Solution (p. 833)).
Results → Graphics → Contours → New...
a. Enter temperature for Contour Name.
b. Enable the Filled option in the Options group box.
c. Select Banded in the Coloring group box.
d. Select Temperature... and Static Temperature from the Contours of drop-down lists.
e. Click Save/Display (Figure 21.3: Contours of Temperature for the Steady Conduction Solution (p. 833)) and close the Contours dialog box.
The temperature contour definition appear under the Results/Graphics/Contours tree branch.
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Setup and Solution
Figure 21.3: Contours of Temperature for the Steady Conduction Solution
11. Display filled contours of temperature to determine the thickness of mushy zone.
Results → Graphics → Contours → New...
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Modeling Solidification
a. Enter temperature-mushy for Contour Name.
b. Disable Auto Range in the Options group box.
The Clip to Range option is automatically enabled.
c. Enter 1100 for Min and 1200 for Max.
d. Select Banded in the Coloring group box.
e. Enable Draw Mesh in the Options group box.
f.
Deselect default-interior from the Surfaces selection list and close the Mesh Display dialog
box.
g. Click Save/Display (See Figure 21.4: Contours of Temperature (Mushy Zone) for the Steady
Conduction Solution (p. 835)) and close the Contours dialog box.
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Setup and Solution
Figure 21.4: Contours of Temperature (Mushy Zone) for the Steady Conduction Solution
12. Save the case and data files for the steady conduction solution (solid.cas.h5 and solid.dat.h5).
File → Write → Case & Data...
21.4.9. Solution: Transient Flow and Heat Transfer
In this step, you will turn on time dependence and include the flow and swirl velocity equations in the
calculation. You will then solve the transient problem using the steady conduction solution as the initial
condition.
1. Enable a time-dependent solution by selecting Transient from the Time list.
Setup →
General
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Modeling Solidification
2. Set the solution parameters.
Solution → Solution → Methods...
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Setup and Solution
a. Retain the default selection of First Order Implicit from the Transient Formulation dropdown list.
b. Ensure that PRESTO! is selected from the Pressure drop-down list in the Spatial Discretization
group box.
3. Enable calculations for flow and swirl velocity.
Solution → Controls → Equations...
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Modeling Solidification
a. Select Flow and Swirl Velocity and ensure that Energy is selected from the Equations selection
list.
Now all three items in the Equations selection list will be selected.
b. Click OK to close the Equations dialog box.
4. Set the Under-Relaxation Factors.
Solution → Controls → Controls...
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Setup and Solution
a. Enter 0.1 for Liquid Fraction Update.
b. Retain the default values for other Under-Relaxation Factors.
5. Save the initial case and data files (solid01.cas.h5 and solid01.dat.h5).
File → Write → Case & Data...
6. Run the calculation for 2 time steps.
Solution → Run Calculation → Run Calculation...
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Modeling Solidification
a. Enter 0.1 s for Time Step Size.
b. Set the Number of Time Steps to 2.
c. Retain the default value of 20 for Max Iterations/Time Step.
d. Click Calculate.
7. Display filled contours of the temperature after 0.2 seconds using the temperature contours
definition that you created earlier.
Results → Graphics → Contours → temperature
840
Display
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Setup and Solution
Figure 21.5: Contours of Temperature at t=0.2 s
8. Create and display the definition of stream function contours (Figure 21.6: Contours of Stream
Function at t=0.2 s (p. 842)).
Results → Graphics → Contours → New...
a. Enter stream-function for Contour Name.
b. Disable Filled in the Options group box.
c. Disable Global Range.
d. Ensure that the Auto Range is enabled.
e. Select Velocity... and Stream Function from the Contours of drop-down lists.
f.
Click Save/Display.
The stream-function contour definition appear under the Results/Graphics/Contours tree
branch.
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Modeling Solidification
Figure 21.6: Contours of Stream Function at t=0.2 s
As shown in Figure 21.6: Contours of Stream Function at t=0.2 s (p. 842), the liquid is beginning to circulate in a large eddy, driven by natural convection and Marangoni convection on the free surface.
9. Create and display the definition of liquid fraction contours by modifying the stream-function
contour definition (Figure 21.7: Contours of Liquid Fraction at t=0.2 s (p. 843)).
Results → Graphics → Contours → New...
a. Enter liquid-fraction for Contour Name.
b. Enable Filled in the Options group box.
c. Enable Auto Range in the Options group box.
d. Select Solidification/Melting... and Liquid Fraction from the Contours of drop-down lists.
e. Click Save/Display and close the Contours dialog box.
842
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Setup and Solution
Figure 21.7: Contours of Liquid Fraction at t=0.2 s
The liquid fraction contours show the current position of the melt front. Note that in Figure 21.7: Contours
of Liquid Fraction at t=0.2 s (p. 843), the mushy zone divides the liquid and solid regions roughly in
half.
10. Continue the calculation for 48 additional time steps.
Solution → Run Calculation → Run Calculation...
a. Enter 48 for Number of Time Steps.
b. Click Calculate.
After a total of 50 time steps have been completed, the elapsed time will be 5 seconds.
11. Display filled contours of the temperature after 5 seconds using the contour definition created
earlier (Figure 21.8: Contours of Temperature at t=5 s (p. 844)).
Results → Graphics → Contours → temperature
Display
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Modeling Solidification
Figure 21.8: Contours of Temperature at t=5 s
As shown in Figure 21.8: Contours of Temperature at t=5 s (p. 844), the temperature contours are fairly
uniform through the melt front and solid material. The distortion of the temperature field due to the
recirculating liquid is also clearly evident.
In a continuous casting process, it is important to pull out the solidified material at the proper time.
If the material is pulled out too soon, it will not have solidified (that is, it will still be in a mushy state).
If it is pulled out too late, it solidifies in the casting pool and cannot be pulled out in the required shape.
The optimal rate of pull can be determined from the contours of liquidus temperature and solidus
temperature.
12. Display contours of stream function (Figure 21.9: Contours of Stream Function at t=5 s (p. 845)).
Results → Graphics → Contours → stream-function
Display
As shown in Figure 21.9: Contours of Stream Function at t=5 s (p. 845), the flow has developed more
fully by 5 seconds, as compared with Figure 21.6: Contours of Stream Function at t=0.2 s (p. 842) after
0.2 seconds. The main eddy, driven by natural convection and Marangoni stress, dominates the flow.
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Setup and Solution
Figure 21.9: Contours of Stream Function at t=5 s
To examine the position of the melt front and the extent of the mushy zone, you will plot the contours
of liquid fraction.
13. Display filled contours of liquid fraction (Figure 21.10: Contours of Liquid Fraction at t=5 s (p. 846)).
Results → Graphics → Contours → liquid-fraction
Display
The introduction of liquid material at the left of the domain is balanced by the pulling of the solidified
material from the right. After 5 seconds, the equilibrium position of the melt front is beginning to be
established (Figure 21.10: Contours of Liquid Fraction at t=5 s (p. 846)).
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Modeling Solidification
Figure 21.10: Contours of Liquid Fraction at t=5 s
14. Save the case and data files for the solution at 5 seconds (solid5.cas.h5 and solid5.dat.h5).
File → Write → Case & Data...
21.5. Summary
In this tutorial, you studied the setup and solution for a fluid flow problem involving solidification for
the Czochralski growth process.
The solidification model in ANSYS Fluent can be used to model the continuous casting process where
a solid material is continuously pulled out from the casting domain. In this tutorial, you patched a
constant value and a custom field function for the pull velocities instead of computing them. This approach is used for cases where the pull velocity is not changing over the domain, as it is computationally
less expensive than having ANSYS Fluent compute the pull velocities during the calculation.
For more information about the solidification/melting model, see the Fluent User's Guide.
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Chapter 22: Using the Eulerian Granular Multiphase
Model with Heat Transfer
This tutorial is divided into the following sections:
22.1. Introduction
22.2. Prerequisites
22.3. Problem Description
22.4. Setup and Solution
22.5. Summary
22.6. References
22.1. Introduction
This tutorial examines the flow of air and a granular solid phase consisting of glass beads in a hot gas
fluidized bed, under uniform minimum fluidization conditions. The results obtained for the local wallto-bed heat transfer coefficient in ANSYS Fluent can be compared with analytical results [1].
This tutorial demonstrates how to do the following:
• Use the Eulerian granular model.
• Set boundary conditions for internal flow.
• Compile a User-Defined Function (UDF) for the gas and solid phase thermal conductivities.
• Calculate a solution using the pressure-based solver.
22.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
In order to complete the steps to compile the UDF, you will need to have a working C compiler installed
on your machine.
22.3. Problem Description
This problem considers a hot gas fluidized bed in which air flows upwards through the bottom of the
domain and through an additional small orifice next to a heated wall. A uniformly fluidized bed is ex-
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Using the Eulerian Granular Multiphase Model with Heat Transfer
amined, which you can then compare with analytical results [1]. The geometry and data for the problem
are shown in Figure 22.1: Problem Schematic (p. 848).
Figure 22.1: Problem Schematic
22.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
22.4.1. Preparation
22.4.2. Mesh
22.4.3. Solver Settings
22.4.4. Models
22.4.5. UDF
22.4.6. Materials
22.4.7. Phases
22.4.8. Boundary Conditions
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Setup and Solution
22.4.9. Solution
22.4.10. Postprocessing
22.4.1. Preparation
To prepare for running this tutorial:
1.
Download the eulerian_granular_heat.zip file here.
2.
Unzip eulerian_granular_heat.zip to your working directory.
The files fluid-bed.msh and conduct.c can be found in the folder.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
6.
Enable Double Precision under Options.
Note:
The double precision solver is recommended for modeling multiphase flow simulations.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
8.
Ensure that Set up Compilation Environment for UDF is enabled in the Environment tab of
the Fluent Launcher window. This will allow you to compile the UDF.
22.4.2. Mesh
1. Read the mesh file fluid-bed.msh.
File → Read → Mesh...
As ANSYS Fluent reads the mesh file, it will report the progress in the console.
2. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
ANSYS Fluent will perform various checks on the mesh and will report the progress in the console.
Make sure that the reported minimum volume is a positive number.
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Using the Eulerian Granular Multiphase Model with Heat Transfer
3. Examine the mesh (Figure 22.2: Mesh Display of the Fluidized Bed (p. 850)).
Extra:
You can use the right mouse button to check which zone number corresponds to each
boundary. If you click the right mouse button on one of the boundaries in the graphics
window, its zone number, name, and type will be printed in the ANSYS Fluent console.
This feature is especially useful when you have several zones of the same type and you
want to distinguish between them quickly.
Figure 22.2: Mesh Display of the Fluidized Bed
22.4.3. Solver Settings
1. Enable the pressure-based transient solver.
Setup →
850
General
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Setup and Solution
a. Retain the default selection of Pressure-Based from the Type list.
The pressure-based solver must be used for multiphase calculations.
b. Select Transient from the Time list.
c. Enable Gravity.
d. Enter -9.81 m/s2 for the Gravitational Acceleration in the Y direction.
22.4.4. Models
1. Enable the Eulerian multiphase model for two phases.
You will use the default settings for the Eulerian model, so you can enable it directly from the tree by
right-clicking the Multiphase node and choosing Eulerian from the context menu.
Setup → Models → Multiphase
Eulerian
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2. Enable heat transfer by enabling the energy equation.
Setup → Models → Energy
On
An Information dialog box appears reminding you to confirm the property values. Click OK in
the Information dialog box to continue.
3. Enable the laminar viscous model.
The decision to use the laminar model should be based on the Stokes number for the particles suspended
in the fluid flow.
Setup → Models → Viscous
Model → Laminar
22.4.5. UDF
1. Compile the user-defined function, conduct.c, that will be used to define the thermal conductivity for the gas and solid phases.
User Defined → User Defined → Functions → Compiled...
a. Click the Add... button below the Source Files option to open the Select File dialog box.
b. Select the file conduct.c and click OK in the Select File dialog box.
c. Click Build.
ANSYS Fluent will create a libudf folder and compile the UDF. Also, a Warning dialog box will
open asking you to make sure that UDF source file and case/data files are in the same folder.
d. Click OK to close the Warning dialog box.
e. Click Load to load the UDF.
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Setup and Solution
22.4.6. Materials
1. Modify the properties for air, which will be used for the primary phase.
Setup →
Materials →
air → Create/Edit...
The properties used for air are modified to match data used by Kuipers et al. [1]
a. Enter 1.2 kg/m3 for Density.
b. Enter 994 J/kg-K for Cp.
c. Select user-defined from the Thermal Conductivity drop-down list to open the User Defined
Functions dialog box.
i.
Select conduct_gas::libudf from the available list.
ii. Click OK to close the User Defined Functions dialog box.
d. Click Change/Create.
2. Define a new fluid material for the granular phase (the glass beads).
Setup →
Materials →
air → Create/Edit...
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a. Enter solids for Name.
b. Enter 2660 kg/m3 for Density.
c. Enter 737 J/kg-K for Cp.
d. Retain the selection of user-defined from the Thermal Conductivity drop-down list.
e. Click the Edit... button to open the User Defined Functions dialog box.
i.
Select conduct_solid::libudf in the User Defined Functions dialog box and click
OK.
A Question dialog box will open asking if you want to overwrite air.
ii. Click No in the Question dialog box.
f.
Click Change/Create and close the Materials dialog box.
22.4.7. Phases
You will now configure the phases.
Setup → Models → Multiphase
Edit...
1. In the Phases tab of the Multiphase Model dialog box, define air as the primary phase.
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Setup and Solution
a. In the Phases selection list, select phase-1 – Primary Phase.
b. Enter air for Name.
c. Ensure that air is selected from the Phase Material drop-down list.
d. Click Apply.
Important:
When setting up your case, if you have made changes in the current tab, you should
click the Apply button to make them effective before moving to the next tab.
Otherwise, the relevant models may not be available in the other tabs, and your
settings may be lost.
2. Define solids (glass beads) as the secondary phase.
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Using the Eulerian Granular Multiphase Model with Heat Transfer
a. In the Phases selection list, select phase-2 – Secondary Phase.
b. Enter solids for Name.
c. Select solids from the Phase Material drop-down list.
d. Enable Granular.
e. Retain the default selection of Phase Property in the Granular Temperature Model group
box.
f.
Enter 0.0005 m for Diameter.
g. Select syamlal-obrien from the Granular Viscosity drop-down list.
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Setup and Solution
h. Select lun-et-al from the Granular Bulk Viscosity drop-down list.
i.
Select constant from the Granular Temperature drop-down list and enter 1e-05.
j.
Enter 0.6 for the Packing Limit.
k. Click Apply.
3. In the Phases Interaction tab of the Multiphase Model dialog box, define the interphase interactions formulations to be used.
a. In the Forces tab, select syamlal-obrien from the Coefficient drop-down list (Drag Coefficient
group box).
b. Click Apply.
c. Go to the Heat, Mass, Reactions tab.
d. In the Heat tab, select gunn from the Heat Transfer Coefficient drop-down list.
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Using the Eulerian Granular Multiphase Model with Heat Transfer
The interphase heat exchange is simulated, using a drag coefficient, the default restitution coefficient
for granular collisions of 0.9, and a heat transfer coefficient. Granular phase lift is not very relevant
in this problem, and in fact is rarely used.
e. Click Apply.
f.
In the Interfacial Area tab, select ia-symmetric from the Interfacial Area drop-down list.
The default ia-particle method is best suited for typical dispersed flow applications with a volume
fraction lower than 30%. In this analysis, the volume fraction of the secondary phase is relatively
high (close to 60%). The ia-symmetric correlation is more accurate for such cases because it considers the volume fraction of both the primary and secondary phases in the interfacial area calculation.
g. Click Apply and close the Multiphase Model dialog box.
22.4.8. Boundary Conditions
For this problem, you need to set the boundary conditions for all boundaries.
Setup →
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Boundary Conditions
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Setup and Solution
1. Set the boundary conditions for the lower velocity inlet (v_uniform) for the primary phase.
Setup →
Boundary Conditions →
v_uniform
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Using the Eulerian Granular Multiphase Model with Heat Transfer
For the Eulerian multiphase model, you will specify conditions at a velocity inlet that are specific to
the primary and secondary phases.
a. Select air from the Phase drop-down list.
b. Click the Edit... button to open the Velocity Inlet dialog box.
i.
Retain the default selection of Magnitude, Normal to Boundary from the Velocity Specification Method drop-down list.
ii. Enter 0.25 m/s for the Velocity Magnitude.
iii. Click the Thermal tab and enter 293 K for Temperature.
iv. Click Apply and close the Velocity Inlet dialog box.
2. Set the boundary conditions for the lower velocity inlet (v_uniform) for the secondary phase.
Setup →
Boundary Conditions →
v_uniform
a. Select solids from the Phase drop-down list.
b. Click the Edit... button to open the Velocity Inlet dialog box.
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Setup and Solution
i.
Retain the default Velocity Specification Method and Reference Frame.
ii. Retain the default value of 0 m/s for the Velocity Magnitude.
iii. Click the Thermal tab and enter 293 K for Temperature.
iv. Click the Multiphase tab and retain the default value of 0 for Volume Fraction.
v. Click Apply and close the Velocity Inlet dialog box.
3. Set the boundary conditions for the orifice velocity inlet (v_jet) for the primary phase.
Setup →
Boundary Conditions →
v_jet
a. Select air from the Phase drop-down list.
b. Click the Edit... button to open the Velocity Inlet dialog box.
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i.
Retain the default Velocity Specification Method and Reference Frame.
ii. Enter 0.25 m/s for the Velocity Magnitude.
In order for a comparison with analytical results [1] to be meaningful, in this simulation you
will use a uniform value for the air velocity equal to the minimum fluidization velocity at both
inlets on the bottom of the bed.
iii. Click the Thermal tab and enter 293 K for Temperature.
iv. Click Apply and close the Velocity Inlet dialog box.
4. Set the boundary conditions for the orifice velocity inlet (v_jet) for the secondary phase.
Setup →
Boundary Conditions →
v_jet
a. Select solids from the Phase drop-down list.
b. Click the Edit... button to open the Velocity Inlet dialog box.
i.
Retain the default Velocity Specification Method and Reference Frame.
ii. Retain the default value of 0 m/s for the Velocity Magnitude.
iii. Click the Thermal tab and enter 293 K for Temperature.
iv. Click the Multiphase tab and retain the default value of 0 for the Volume Fraction.
v. Click Apply and close the Velocity Inlet dialog box.
5. Set the boundary conditions for the pressure outlet (poutlet) for the mixture phase.
Setup →
862
Boundary Conditions →
poutlet
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Setup and Solution
For the Eulerian granular model, you will specify conditions at a pressure outlet for the mixture and
for both phases.
The thermal conditions at the pressure outlet will be used only if flow enters the domain through this
boundary. You can set them equal to the inlet values, as no flow reversal is expected at the pressure
outlet. In general, however, it is important to set reasonable values for these downstream scalar values,
in case flow reversal occurs at some point during the calculation.
a. Select mixture from the Phase drop-down list.
b. Click the Edit... button to open the Pressure Outlet dialog box.
i.
Retain the default value of 0 Pascal for Gauge Pressure.
ii. Click Apply and close the Pressure Outlet dialog box.
6. Set the boundary conditions for the pressure outlet (poutlet) for the primary phase.
Setup →
Boundary Conditions →
poutlet
a. Select air from the Phase drop-down list.
b. Click the Edit... button to open the Pressure Outlet dialog box.
i.
In the Thermal tab, enter 293 K for Backflow Total Temperature.
ii. Click Apply and close the Pressure Outlet dialog box.
7. Set the boundary conditions for the pressure outlet (poutlet) for the secondary phase.
Setup →
Boundary Conditions →
poutlet
a. Select solids from the Phase drop-down list.
b. Click the Edit... button to open the Pressure Outlet dialog box.
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Using the Eulerian Granular Multiphase Model with Heat Transfer
i.
In the Thermal tab, enter 293 K for the Backflow Total Temperature.
ii. In the Multiphase tab, retain default settings.
iii. Click Apply and close the Pressure Outlet dialog box.
8. Set the boundary conditions for the heated wall (wall_hot) for the mixture.
Setup →
Boundary Conditions →
wall_hot
For the heated wall, you will set thermal conditions for the mixture, and momentum conditions (zero
shear) for both phases.
a. Select mixture from the Phase drop-down list.
b. Click the Edit... button to open the Wall dialog box.
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Setup and Solution
i.
In the Thermal tab, select Temperature from the Thermal Conditions list.
ii. Enter 373 K for Temperature.
iii. Click Apply and close the Wall dialog box.
9. Set the boundary conditions for the heated wall (wall_hot) for the primary phase.
Setup →
Boundary Conditions →
wall_hot
a. Select air from the Phase drop-down list.
b. Click the Edit... button to open the Wall dialog box.
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Using the Eulerian Granular Multiphase Model with Heat Transfer
c. Retain the default No Slip condition and click Apply and close the Wall dialog box.
10. Set the boundary conditions for the heated wall (wall_hot) for the secondary phase (solids) same
as that of the primary phase.
Setup →
Boundary Conditions →
wall_hot
For the secondary phase, you will retain the default no slip condition as for the primary phase.
11. Set the boundary conditions for the adiabatic wall (wall_ins).
Setup →
Boundary Conditions →
wall_ins
For the adiabatic wall, retain the default thermal conditions for the mixture (zero heat flux), and the
default momentum conditions (no slip) for both phases.
22.4.9. Solution
1. Select the second order implicit transient formulation and higher-order spatial discretization
schemes.
Solution → Solution → Methods...
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Setup and Solution
a. Select Second Order Implicit from the Transient Formulation drop-down list.
b. Modify the discretization methods in the Spacial Discretization group box.
i.
Select Second Order Upwind for Pressure and Momentum.
ii. Select QUICK for Volume Fraction and Energy.
2. Set the solution parameters.
Solution → Controls → Controls...
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Using the Eulerian Granular Multiphase Model with Heat Transfer
a. Enter 0.5 for Pressure.
b. Enter 0.2 for Momentum.
3. Ensure that the plotting of residuals is enabled during the calculation.
Solution → Reports → Residuals...
4. Define a custom field function for the heat transfer coefficient.
User Defined → Field Functions → Custom...
Initially, you will define functions for the mixture temperature, and thermal conductivity, then you will
use these to define a function for the heat transfer coefficient.
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Setup and Solution
a. Define the function t_mix.
i.
Select Temperature... and Static Temperature from the Field Functions drop-down lists.
ii. Ensure that air is selected from the Phase drop-down list and click Select.
iii. Click the multiplication symbol in the calculator pad.
iv. Select Phases... and Volume fraction from the Field Functions drop-down list.
v. Ensure that air is selected from the Phase drop-down list and click Select.
vi. Click the addition symbol in the calculator pad.
vii. Similarly, add the term solids-temperature * solids-vof.
viii.Enter t_mix for New Function Name.
ix. Click Define.
b. Define the function k_mix.
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i.
Select Properties... and Thermal Conductivity from the Field Functions drop-down lists.
ii. Select air from the Phase drop-down list and click Select.
iii. Click the multiplication symbol in the calculator pad.
iv. Select Phases... and Volume fraction from the Field Functions drop-down lists.
v. Ensure that air is selected from the Phase drop-down list and click Select.
vi. Click the addition symbol in the calculator pad.
vii. Similarly, add the term solids-thermal-conductivity-lam * solids-vof.
viii.Enter k_mix for New Function Name.
ix. Click Define.
c. Define the function ave_htc.
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Setup and Solution
i.
Click the subtraction symbol in the calculator pad.
ii. From the Field Functions drop-down lists, select Custom Field Functions... and k_mix
and click Select.
iii. Use the calculator pad and the Field Functions lists to complete the definition of the
function.
iv. Enter ave_htc for New Function Name.
v. Click Define and close the Custom Field Function Calculator dialog box.
5. Define the point surface in the cell next to the wall on the plane
.
Domain → Surface → Create → Point...
a. Enter y=0.24 for New Surface Name.
b. Enter 0.28494 m for x and 0.24 m for y in the Coordinates group box.
c. Click Create and close the Point Surface dialog box.
6. Create a surface report definition for the heat transfer coefficient.
Solution → Reports → Definitions → New → Surface Report → Facet Average...
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Using the Eulerian Granular Multiphase Model with Heat Transfer
a. Enter surf-mon-1 for Name of the surface report definition.
b. In the Create group box, enable Report File, Report Plot and Print to Console.
c. Select Custom Field Functions... and ave_htc from the Field Variable drop-down lists.
d. Select y=0.24 from the Surfaces selection list.
e. Click OK to save the surface report definition settings and close the Surface Report Definition
dialog box.
surf-mon-1-rplot and surf-mon-1-rfile that are automatically generated by Fluent appear in
the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report Files, respectively).
f.
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Rename the report output file.
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Setup and Solution
Solution → Monitors → Report Files → surf-mon-1-rfile
i.
Edit...
Enter htc-024.out for Output File Base Name.
ii. Click OK to close the Edit Report File dialog box.
7. Define a cell register for the lower half of the fluidized bed.
Solution → Cell Registers
New → Region...
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Using the Eulerian Granular Multiphase Model with Heat Transfer
a. Enter 0.3 m for Xmax and 0.5 m for Ymax in the Input Coordinates group box.
b. Click Save and close the Region Register dialog box.
This register is used to patch the initial volume fraction of solids in the next step.
8. Initialize the solution.
Solution → Initialization → Options...
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Setup and Solution
a. Select all-zones from the Compute from drop-down list.
b. Retain the default values and click Initialize.
9. Patch the initial volume fraction of solids in the lower half of the fluidized bed.
Solution → Initialization → Patch...
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Using the Eulerian Granular Multiphase Model with Heat Transfer
a. Select solids from the Phase drop-down list.
b. Select Volume Fraction from the Variable selection list.
c. Enter 0.598 for Value.
d. Select region_0 from the Registers to Patch selection list.
e. Click Patch and close the Patch dialog box.
At this point, it is a good practice to display contours of the variable you just patched, to ensure that
the desired field was obtained.
10. Display contours of Volume Fraction of solids (Figure 22.3: Initial Volume Fraction of Granular
Phase (solids) (p. 877)).
Results → Graphics → Contours → New...
a. Enable Filled in the Options group box.
b. Select Phases... from the upper Contours of drop-down list.
c. Select solids from the Phase drop-down list.
d. Ensure that Volume fraction is selected from the lower Contours of drop-down list.
e. Click Display and close the Contours dialog box.
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Setup and Solution
Figure 22.3: Initial Volume Fraction of Granular Phase (solids)
11. Save the case file (fluid-bed.cas.h5).
File → Write → Case...
12. Start calculation.
Solution → Run Calculation → Run Calculation...
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Using the Eulerian Granular Multiphase Model with Heat Transfer
a. Set 0.00015 for Time Step Size(s).
b. Set 12000 for Number of Time Steps.
c. Enter 50 for Max Iterations/Time Step.
d. Click Calculate.
The plot of the value of the mixture-averaged heat transfer coefficient in the cell next to the heated
wall versus time is in excellent agreement with results published for the same case [1].
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Setup and Solution
Figure 22.4: Plot of Mixture-Averaged Heat Transfer Coefficient in the Cell Next to the Heated
Wall Versus Time
13. Save the case and data files (fluid-bed.cas.h5 and fluid-bed.dat.h5).
File → Write → Case & Data...
22.4.10. Postprocessing
1. Display the pressure field in the fluidized bed (Figure 22.5: Contours of Static Pressure (p. 881)).
Results → Graphics → Contours → New...
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Using the Eulerian Granular Multiphase Model with Heat Transfer
a. Enter contour-pressure for Contour Name.
b. Select Banded in the Coloring group box.
c. Select mixture from Phase drop-down list.
d. Select Pressure... and Static Pressure from the Contours of drop-down lists.
e. Click Save/Display and close the Contours dialog box.
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Figure 22.5: Contours of Static Pressure
Note the build-up of static pressure in the granular phase.
2. Display the volume fraction of solids (Figure 22.6: Contours of Volume Fraction of Solids (p. 882)).
Results → Graphics → Contours → New...
a. Enter contour-solid-vf for Contour Name.
b. Select Banded in the Coloring group box.
c. Select solids from the Phase drop-down list.
d. Select Phases... and Volume fraction from the Contours of drop-down lists.
e. Click Save/Display and close the Contours dialog box.
f.
Zoom in to show the contours close to the region where the change in volume fraction is the
greatest.
Note that the region occupied by the granular phase has expanded slightly, as a result of fluidization.
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Figure 22.6: Contours of Volume Fraction of Solids
3. Save the case file (fluid-bed.cas.h5).
File → Write → Case...
22.5. Summary
This tutorial demonstrated how to set up and solve a granular multiphase problem with heat transfer,
using the Eulerian model. You learned how to set boundary conditions for the mixture and both phases.
The solution obtained is in excellent agreement with analytical results from Kuipers et al. [1].
22.6. References
1. J. A. M. Kuipers, W. Prins, and W. P. M. Van Swaaij "Numerical Calculation of Wall-to-Bed Heat
Transfer Coefficients in Gas-Fluidized Beds", Department of Chemical Engineering, Twente University
of Technology, in AIChE Journal, July 1992, Vol. 38, No. 7.
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Chapter 23: Modeling One-Way Fluid-Structure
Interaction (FSI) Within Fluent
This tutorial is divided into the following sections:
23.1. Introduction
23.2. Prerequisites
23.3. Problem Description
23.4. Setup and Solution
23.5. Summary
23.1. Introduction
This tutorial examines turbulent air flow through a cylindrical test chamber that includes a steel probe.
You will enable a structural model in order to simulate the deformation of the probe as a result of the
fluid flow. It is assumed that the deformation will be small enough that this problem can be modeled
as a one-way fluid-structure interaction (FSI) simulation; that is, the fluid flow will affect the deformation
of the structure, but not vice versa. Because Fluent performs all of the structural calculations (as opposed
to using a separate structural program), it is referred to as "intrinsic FSI".
This tutorial demonstrates how to do the following:
• Run a journal file to complete an initial fluid flow simulation without structural calculations.
• Enable a structural model.
• Define structural material properties, a solid cell zone, and related boundary conditions.
• Turn off flow and turbulence equations.
• Complete a one-way FSI simulation.
• Postprocess the deformation of a solid cell zone.
23.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
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23.3. Problem Description
The problem to be modeled in this tutorial is shown schematically in Figure 23.1: Problem Schematic (p. 884).
Figure 23.1: Problem Schematic
Taking advantage of the symmetry of the problem, only half of the geometry is modeled. The cylindrical
test chamber is 20 cm long, with a diameter of 10 cm. Turbulent air enters the chamber at 100 m/s,
flows around and through the steel probe, and exits through a pressure outlet.
23.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
23.4.1. Preparation
23.4.2. Structural Model
23.4.3. Materials
23.4.4. Cell Zone Conditions
23.4.5. Boundary Conditions
23.4.6. Solution
23.4.7. Postprocessing
23.4.1. Preparation
To prepare for running this tutorial:
1.
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Download the fsi_1way.zip file here.
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Setup and Solution
2.
Unzip fsi_1way.zip to your working directory.
The files probe.msh and fluid_flow.jou can be found in the folder. Note that the solid cell
zone in the mesh file is appropriate for a 3D intrinsic FSI simulation, which requires that only hexahedral, tetrahedral, wedge, and/or pyramid cell types are used and that a conformal mesh exists
between the solid and fluid zones.
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Retain the default Solver Processes to 1 under Parallel (Local Machine).
8.
Make sure that the Working Directory (in the General Options tab) is set to the one created
when you unzipped fsi_1way.zip.
9.
Read the journal file fluid_flow.jou.
File → Read → Journal...
This journal file will read the mesh file probe.msh and set up and solve a fluid flow simulation that
will serve as the starting point for the structural calculations. It is not necessary to separate these
calculations, but it is a advantage of one-way FSI simulation that structural calculations can be simply
added to an existing fluid flow case and data file. Separating the calculations allows you to easily
discern and resolve any convergence issues that are solely related to the fluid simulation.
As Fluent reads the journal file, it will report the text commands and solution progress in the console.
You can also view the journal file in a text editor to see the settings used in this simulation. The final
text command in the journal file will display contours of the velocity magnitude (Figure 23.2: Velocity
Magnitude on the Symmetry Plane (p. 886)).
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Figure 23.2: Velocity Magnitude on the Symmetry Plane
10. Save the initial case and data files as probe_fluid.cas.h5 and probe_fluid.dat.h5.
File → Write → Case & Data...
Having completed the initial fluid flow simulation, the remaining steps are all concerned with setting up
the structural calculations and obtaining the deformation results for the solid cell zone as a result of the
flow pressure.
23.4.2. Structural Model
1. Verify that a solid cell zone is already defined, as this is necessary to be able to enable a structural
model. You can view the existing cell zones in the Outline View window.
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2. Enable the linear elasticity structural model.
Setup → Models → Structure
Edit...
a. Select Linear Elasticity from the Model list.
This model enables structural calculations for the solid cell zone such that the internal load is linearly
proportional to the nodal displacement, and the structural stiffness matrix remains constant.
b. Click OK to close the Structural Model dialog box.
23.4.3. Materials
1. Add steel to the list of solid materials by copying it from the ANSYS Fluent materials database.
Setup → Materials → Solid → aluminum
Edit...
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a. Click the Fluent Database... button in the Create/Edit Materials dialog box to open the
Fluent Database Materials dialog box.
i.
Select solid from the Material Type drop-down list.
ii. Select steel in the Fluent Solid Materials selection list.
Scroll down the list to find steel. Selecting this item will display the default properties in the
dialog box.
iii. Click Copy and close the Fluent Database Materials dialog box.
The Create/Edit Materials dialog box will now display the copied properties for steel.
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Setup and Solution
b. Keep the default values for the material.
c. Click Change/Create and close the Create/Edit Materials dialog box.
23.4.4. Cell Zone Conditions
1. Set up the cell zone conditions for the solid zone associated with the probe (solid).
Setup → Cell Zone Conditions → Solid → solid
Edit...
a. Select steel from the Material Name drop-down list.
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b. Click Apply and close the Solid dialog box.
23.4.5. Boundary Conditions
You must ensure that the boundary conditions are appropriately defined for every wall that is immediately adjacent to the solid zone.
1. Set the boundary conditions for solid-top, which is located where the probe attaches to the top
of the test chamber. You will define it as being fixed (that is, undergoing no displacement).
Setup → Boundary Conditions → Wall → solid-top
Edit...
a. Click the Structure tab.
b. Select displacement boundary conditions (that is, Node X-Displacement from the X-Displacement Boundary Condition drop-down list with 0 for the X-Displacement, and so on).
c. Click Apply and close the Wall dialog box.
2. Set the boundary conditions for all of the wall zones of the solid cell zone that lie on the plane
of symmetry and represent the center of the probe. In this case there are two: they should be
free to move with no stress in the X- and Y-directions, but fixed in the Z-direction.
a. Set the boundary conditions for solid-symmetry.
Setup → Boundary Conditions → Wall → solid-symmetry
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i.
Click the Structure tab.
ii. Select Stress Free from the X- and Y-Displacement Boundary Condition drop-down lists.
iii. Select the Z-Displacement Boundary Condition drop-down list and the Z-Displacement
field (that is, Node Z-Displacement and set 0, respectively).
This ensures that the zone does not move out of the plane of symmetry.
iv. Click Apply and close the Wall dialog box.
b. Copy the boundary conditions from solid-symmetry to solid-symmetry:011.
Setup → Boundary Conditions → Wall → solid-symmetry
i.
Copy...
Make sure that solid-symmetry is selected in the From Boundary Zone list.
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ii. Select solid-symmetry:011 in the To Boundary Zones list.
iii. Click the Copy button.
A Question dialog box will open, asking if you want to copy the boundary conditions to all of
the selected zones. Click OK.
iv. Close the Copy Conditions dialog box.
3. Set the boundary conditions for all of the two-sided walls (that is, the wall / wall-shadow pairs)
between the solid and fluid cell zones. In this case there is one pair of walls, which represent the
outer surface of the probe.
a. Set the boundary conditions for fsisurface-solid-shadow.
Setup → Boundary Conditions → Wall → fsisurface-solid-shadow
Edit...
Note that the Adjacent Cell Zone for this wall is flow, which is the fluid zone. The side of the wall
/ wall-shadow pair that is immediately adjacent to the fluid does not require any settings in the
Structure tab, and so this tab is not available.
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Setup and Solution
i.
Retain the default settings in the Momentum tab.
ii. Click Apply and close the Wall dialog box.
b. Set the boundary conditions for fsisurface-solid.
Setup → Boundary Conditions → Wall → fsisurface-solid
Edit...
Note that the Adjacent Cell Zone for this wall is solid, which is the solid zone. The side of the
wall / wall-shadow pair that is immediately adjacent to the solid does require structural settings
(that is, displacement boundary conditions).
i.
Click the Structure tab.
ii. Select Intrinsic FSI from the X-, Y-, and Z-Displacement Boundary Condition drop-down
lists.
This specifies that the displacement results from pressure loads exerted by the fluid flow on the
faces. This setting is only available for two-sided walls.
iii. Click Apply and close the Wall dialog box.
23.4.6. Solution
1. Enable the inclusion of operating pressure into the fluid-structure interaction force by entering
the following text command:
> define/models/structure/expert/include-pop-in-fsi-force?
Include operating p into fsi force [no] yes
2. Review the convergence criteria for the displacement residual equations.
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Solution → Monitors → Residual
Edit...
a. Retain the default settings for the x-, y-, and z-displacement equations.
b. Click OK to close the Residual Monitors dialog box.
3. Disable the flow and turbulence equations, since in a one-way FSI simulation they will not change
from their converged state.
Solution → Controls
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Equations...
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Setup and Solution
a. Deselect Flow and Turbulence from the Equations selection list.
b. Retain the selection of Structure.
c. Click OK to close the Equations dialog box.
4. Save the case file (probe_fsi_1way.cas.h5).
File → Write → Case...
5. Start the calculation by requesting 2 iterations in the Solution ribbon tab (Run Calculation group
box)..
Solution → Run Calculation
a. Enter 2 for No. of Iterations.
Since only structural calculations will be performed, you do not need a large number of iterations
to reach convergence.
b. Click Calculate.
6. After the solution has been calculated, save the case and data files (probe_fsi_1way.cas.h5
and probe_fsi_1way.dat.h5).
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File → Write → Case & Data...
23.4.7. Postprocessing
1. Display the total displacement of the probe (Figure 23.3: Contours of Total Displacement (p. 897)).
Results → Graphics → Contours → New...
a. Enter contour-disp for Contour Name.
b. Select Structure... and Total Displacement from the Contours of drop-down lists.
c. Deselect all surfaces in the Surfaces selection list by clicking
, and then select solid.
d. Click Save/Display, close the Contours dialog box, and rotate and magnify the view as shown
in Figure 23.3: Contours of Total Displacement (p. 897).
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Summary
Figure 23.3: Contours of Total Displacement
2. Save the case file (probe_fsi_1way.cas.h5).
File → Write → Case...
23.5. Summary
This tutorial demonstrated how to set up and solve a one-way intrinsic FSI simulation. You learned how
to enable a structural model and define the solid material and boundary conditions. After completing
the simulation, you displayed the resulting displacement of the structure. For more information about
intrinsic FSI simulations, see the Fluent User's Guide.
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Chapter 24: Modeling Two-Way Fluid-Structure
Interaction (FSI) Within Fluent
This tutorial is divided into the following sections:
24.1. Introduction
24.2. Prerequisites
24.3. Problem Description
24.4. Setup and Solution
24.5. Summary
24.1. Introduction
This tutorial examines turbulent air flow through a duct that includes vertical flaps. You will enable a
structural model in order to simulate the deformation of the flaps as a result of the fluid flow. It is assumed that the deformation will be large enough that this problem must be modeled as a two-way
fluid-structure interaction (FSI) simulation; that is, the fluid flow will affect the deformation of the
structures, and vice versa. Because Fluent performs all of the structural calculations (as opposed to using
a separate structural program), it is referred to as "intrinsic FSI".
This tutorial demonstrates how to do the following:
• Run a journal file to complete an initial steady-state fluid flow simulation without structural calculations.
• Set up a transient calculation.
• Enable a structural model.
• Define structural material properties, a solid cell zone, and related boundary conditions.
• Set up dynamic mesh zones for the fluid-structure interaction.
• Create solution animation definitions for a scene, contour, and mesh.
• Complete a two-way FSI simulation.
• Postprocess the fluid flow and the deformation of a solid cell zone.
24.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
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24.3. Problem Description
The problem to be modeled in this tutorial is shown schematically in Figure 24.1: Problem Schematic (p. 900).
Figure 24.1: Problem Schematic
Flow through a simple duct with vertical flaps is simulated as a 2D planar model. The duct is 10 cm
long and 4 cm high, and the flaps are 1 cm tall and 0.3 cm thick, composed of silicone rubber. Turbulent
air enters the duct at 10 m/s, flows around the flaps, and exits through a pressure outlet. Symmetry allows
only half of the duct to be modeled.
24.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
24.4.1. Preparation
24.4.2. Solver and Analysis Type
24.4.3. Structural Model
24.4.4. Materials
24.4.5. Cell Zone Conditions
24.4.6. Boundary Conditions
24.4.7. Dynamic Mesh Zones
24.4.8. Solution Animations
24.4.9. Solution
24.4.10. Postprocessing
24.4.1. Preparation
To prepare for running this tutorial:
1. Download the fsi_2way.zip file here.
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Setup and Solution
2. Unzip fsi_2way.zip to your working directory.
The files flap.msh and steady_fluid_flow.jou can be found in the folder. Note that the cell
zone in the mesh file that will represent the solid zone is appropriate for a 2D intrinsic FSI simulation,
which requires that only quadrilateral and/or triangular cell types are used and that a conformal mesh
exists between the zones that will represent the solid and the fluid.
3. Use the Fluent Launcher to start ANSYS Fluent.
4. Select Solution in the top-left selection list to start Fluent in Solution Mode.
5. Select 2D under Dimension.
6. Enable Double Precision under Options.
7. Retain the default Solver Processes to 1 under Parallel (Local Machine).
8. Make sure that the Working Directory (in the General Options tab) is set to the one created
when you unzipped fsi_2way.zip.
9. Read the journal file steady_fluid_flow.jou.
File → Read → Journal...
This journal file will read the mesh file flap.msh and set up and solve a steady fluid flow simulation
that will serve as the starting point for the transient FSI simulation. Solving the steady flow problem
first allows you to easily discern and resolve any convergence issues that are not related to the fluidstructure interaction.
As Fluent reads the journal file, it will report the text commands and solution progress in the console.
You can also view the journal file in a text editor to see the settings used in this simulation. The final
text command in the journal file will display contours of the velocity magnitude (Figure 24.2: SteadyState Velocity Magnitude (p. 902)).
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Figure 24.2: Steady-State Velocity Magnitude
10. Mirror the display across the centerline (Figure 24.3: Duct with Mirroring (p. 903)).
View → Display → Views...
a. Select symmetry.2 in the Mirror Planes selection list.
b. Click Apply to refresh the display.
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c. Close the Views dialog box and reposition the view as shown in Figure 24.3: Duct with Mirroring (p. 903).
Figure 24.3: Duct with Mirroring
11. Save the initial case and data files as flap_fluid.cas.h5 and flap_fluid.dat.h5.
File → Write → Case & Data...
Having completed an initial steady fluid flow simulation, the remaining steps are all concerned with setting
up the structural calculations and obtaining the transient results for the deformation of the solid flaps.
24.4.2. Solver and Analysis Type
1. Specify the solver settings.
Setup →
General
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a. Enable a time-dependent calculation by selecting Transient in the General task page (Solver
group).
b. Retain the default selection of Pressure-Based from the Type list.
24.4.3. Structural Model
1. Verify that a solid cell zone is already defined, as this is necessary to be able to enable a structural
model. You can view the existing cell zones in the Outline View window.
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Setup and Solution
2. Enable the linear elasticity structural model.
Setup → Models → Structure
Edit...
a. Select Linear Elasticity from the Model list.
This model enables structural calculations for the solid cell zone such that the internal load is linearly
proportional to the nodal displacement, and the structural stiffness matrix remains constant.
b. Click OK to close the Structural Model dialog box.
24.4.4. Materials
1. Create a new solid material for the flap.
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Setup → Materials → Solid
New...
a. Enter silicone-rubber for the Name.
b. Clear the Chemical Formula field.
c. Enter 1600 for the Density.
d. Enter 1e+6 for the Youngs Modulus.
e. Enter 0.47 for the Poisson Ratio.
f.
Click Change/Create, and click Yes in the Question dialog box to overwrite solid-1.
g. Close the Create/Edit Materials dialog box.
24.4.5. Cell Zone Conditions
1. Set up the cell zone conditions for the solid zone associated with the flap (solid.5).
Setup → Cell Zone Conditions → Solid → solid.5
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Setup and Solution
a. Select silicone-rubber from the Material Name drop-down list.
b. Click Apply and close the Solid dialog box.
24.4.6. Boundary Conditions
You must ensure that the boundary conditions are appropriately defined for every wall that is immediately adjacent to the solid zone.
1. Set the boundary conditions for flap_attach, which is located where the flap attaches to the duct.
You will define it as being fixed (that is, undergoing no displacement).
Setup → Boundary Conditions → Wall → flap_attach
Edit...
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a. In the Structure tab, select displacement boundary conditions (that is, Node X-Displacement
from the X-Displacement Boundary Condition drop-down list with 0 for the X-Displacement,
and so on).
b. Click Apply and close the Wall dialog box.
2. Set the boundary conditions for all of the two-sided walls (that is, the wall / wall-shadow pairs)
between the solid and fluid cell zones. In this case there is one pair of walls, which represent the
outer surface of the flap.
a. Set the boundary conditions for flap_wall.
Setup → Boundary Conditions → Wall → flap_wall-shadow
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Edit...
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Setup and Solution
Note that the Adjacent Cell Zone for this wall is fluid.4, which is the fluid zone. The side of the
wall / wall-shadow pair that is immediately adjacent to the fluid does not require any settings in
the Structure tab, and so this tab is not available.
i.
Retain the default settings in the Momentum tab.
ii. Click Apply and close the Wall dialog box.
b. Set the boundary conditions for interior_fsi-shadow.
Setup → Boundary Conditions → Wall → flap_wall
Edit...
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Note that the Adjacent Cell Zone for this wall is solid.5, which is the solid zone. The side of the
wall / wall-shadow pair that is immediately adjacent to the solid does require structural settings
(that is, displacement boundary conditions).
i.
Click the Structure tab.
ii. Select Intrinsic FSI from the X- and Y-Displacement Boundary Condition drop-down
lists.
This specifies that the displacement results from pressure loads exerted by the fluid flow on the
faces. This setting is only available for two-sided walls.
iii. Click Apply and close the Wall dialog box.
24.4.7. Dynamic Mesh Zones
For two-way FSI simulations, you must define dynamic mesh properties to allow the mesh to handle
the deformation of the solid zone.
Domain → Mesh Models → Dynamic Mesh...
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Setup and Solution
1. Enable the Dynamic Mesh option.
2. Make sure that the Smoothing option is enabled in the Mesh Methods group box, and click the
Settings... button to open the Mesh Method Settings dialog box.
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a. Select Linearly Elastic Solid from the Method list.
b. Click OK to close the Mesh Method Settings dialog box.
3. Retain the default settings in the Options group box (that is, with the options disabled). These
options are not supported for FSI simulations, except for Implicit Update. The Implicit Update
option may be required for more complex cases in which the stability of the FSI simulation may
be an issue, but for a simple case such as this one, it is not required.
4. Click the Create/Edit... button to open the Dynamic Mesh Zones dialog box.
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a. Select po.3 (the pressure outlet) from the Zone Names drop-down list, select Stationary from
the Type list, and click Create. This ensures the boundary zone does not deform.
b. In a similar manner, create stationary dynamic zones for the other boundary zones that are
not deforming: symmetry.2, velocity_inlet.1, and wall.
c. Select flap_wall-shadow (the side of the wall / wall-shadow pair that is immediately adjacent
to the fluid) from the Zone Names drop-down list, select Intrinsic FSI from the Type list, and
click Create. This specifies that the wall / wall-shadow pair deforms according to the deformation of the adjacent solid zone.
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d. Close the Dynamic Mesh Zones dialog box.
24.4.8. Solution Animations
By setting up animation definitions, you will be able to capture results for your transient simulation
as it calculates the solution, so that you can later display how the fluid flow and flap shape change
over time.
1. Create a scene that can be used in an animation definition for the fluid flow.
Scenes are used when you want to display multiple graphics objects within a single window. In this
case, the animation will include not only contours of the fluid velocity, but also boundary zones.
Results → Scene
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New...
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Setup and Solution
a. Enter vel_bound for the Name.
b. Click New Object and select Mesh... from the drop-down list to open the associated dialog
box.
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
i.
Enter boundaries for the Mesh Name.
ii. Select Edges under the Options list.
iii. Deselect all surfaces in the Surfaces selection list by clicking
shadow, po.3, velocity_inlet.1, and wall.
, and then select flap_wall-
iv. Click Save/Display and close the Mesh Display dialog box.
c. Click New Object and select Contours... from the drop-down list to open the associated dialog
box.
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Setup and Solution
i.
Enter vel_mag for the Contour Name.
ii. Select Velocity... and Velocity Magnitude from the Contours of drop-down lists.
iii. Disable the Auto Range option and enter 20 and 29 for the Min and Max, respectively.
Disabling the Auto Range ensures that all of the results in the animation have the same scale.
The velocity of the fluid will not change very much in this particular solution, and so using a
narrow range of values will make it easier to identify the small contour changes.
iv. Deselect all surfaces in the Surfaces selection list by clicking
.
For 2D cases, if no surface is selected, contouring is done on the entire domain.
v. Click the Save/Display button and close the Contours dialog box.
d. Click the Save & Display button, and then click Cancel to close the Scene dialog box.
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
2. Create an animation definition for the fluid velocity and boundaries scene.
Solution → Calculation Activities → Solution Animations
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New...
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Setup and Solution
a. Enter vel_animation for the Name.
b. Enter 5 for Record after every and select iteration from the drop-down list.
c. Select In Memory from the Storage Type drop-down.
The In Memory option is acceptable for a small 2D case such as this. For larger 2D or 3D cases,
saving animation files with either the PPM Image or HSF File option is preferable, to avoid using
too much of your machine’s memory.
d. Select vel_bound from the Animation Object list.
e. Click OK to create the animation definition.
3. Create an animation definition for the flap displacement.
Solution → Calculation Activities → Solution Animations
New...
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
a. Enter disp_animation for the Name.
b. Enter 5 for Record after every and select iteration from the drop-down list.
c. Select In Memory from the Storage Type drop-down.
d. Click New Object and select Contours... from the drop-down list to open the associated dialog
box.
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Setup and Solution
i.
Enter disp for the Contour Name.
ii. Select Structure... and Total Displacement from the Contours of drop-down lists.
iii. Disable Auto Range and enter 0 and 5.1e-05 for Min and Max, respectively.
iv. Select solid.5 from the Surfaces list.
v. Click Save/Display and close the Contours dialog box.
e. Select disp from the Animation Object list.
f.
Click OK to create the animation definition.
4. Create an animation definition for the mesh.
Solution → Calculation Activities → Solution Animations
New...
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
a. Enter mesh_animation for the Name.
b. Enter 5 for Record after every and select iteration from the drop-down list.
c. Select In Memory from the Storage Type drop-down.
d. Click New Object and select Mesh... from the drop-down list to open the associated dialog
box.
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Setup and Solution
i.
Enter mesh for the Mesh Name.
ii. Disable the Faces option.
iii. Deselect all surfaces in the Surfaces selection list by clicking
and solid.5.
, and then select fluid.4
iv. Click Save/Display and close the Mesh Display dialog box.
e. Select mesh from the Animation Object list.
f.
Click OK to create the animation definition.
5. Add a structural point surface to a location of interest within the solid zone.
Results → Surfaces
New → Structural Point...
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
The Structural Point Surface dialog appears, as does a point triad in the graphics window. Zoom
into the mesh displayed in the graphics window to focus on the tip of the flap.
a. Enter structural-point-flap for the Name.
b. Enter 0.0505 for the x coordinate, and enter 0.0095 for the y coordinate.
Alternatively,you can use the mouse to drag the point's position in the graphics window to an approximate location.
c. Click Create to create the structural point surface at this location.
d. Close the Structural Point Surface dialog box.
6. Create a report definition to monitor displacement of the flap.
Solution → Report Definitions
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New → Surface Report → Vertex Average...
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Setup and Solution
a. Enter report-def-surf for the Name.
b. Select Structure... and Total Displacement from the Contours of drop-down lists.
c. Select structural-point-flap from the Surfaces list.
d. Enable the Report File, Report Plot, and Print to Console options.
e. Click OK.
This report definition will monitor and plot the vertex average of the displacement of the nodes that
surround the structural point surface.
24.4.9. Solution
1. Disable the checking of convergence for the displacement residual equations.
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
Solution → Monitors → Residual
Edit...
a. Disable the Check Convergence options for the x- and y-displacement equations.
b. Click OK to close the Residual Monitors dialog box.
2. Save the case file (flap_fsi_2way.cas.h5).
File → Write → Case...
3. Start the calculation.
Solution → Run Calculation → Run Calculation...
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Setup and Solution
a. Enter 50 for Number of Time Steps.
b. Enter 0.0005 for Time Step Size.
c. Enter 40 for Max Iterations/Time Step.
d. Click Calculate.
4. After the solution has been calculated, save the case and data files (flap_fsi_2way.cas.h5
and flap_fsi_2way.dat.h5).
File → Write → Case & Data...
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
24.4.10. Postprocessing
1. View the displacement of the flap's point surface (Figure 24.4: The Vertex Average Displacement
of the Flap's Point Surface (p. 928)).
Figure 24.4: The Vertex Average Displacement of the Flap's Point Surface
The monitored plot of the vertex average of the displacement at the point surface clearly shows displacement over time.
2. View the animations of the results.
Results → Animations → Playback
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Edit...
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Setup and Solution
a. Select Auto Repeat from the Playback Mode drop-down list.
b. Disable the Use Stored View option.
c. Select vel_animation from the Animation Sequences list.
d. Decrease the Replay Speed by clicking the
button four times.
e. Click the play button (the second from the right in the group of buttons in the Playback group
box).
f.
Magnify the view as shown in Figure 24.5: Contours of Velocity Magnitude (p. 930).
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
Figure 24.5: Contours of Velocity Magnitude
g. Click the
button to stop the animation.
h. Select disp_animation from the Animation Sequences list.
930
i.
Click the play button.
j.
Magnify the view as shown in Figure 24.6: Contours of Total Displacement (p. 931).
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Setup and Solution
Figure 24.6: Contours of Total Displacement
k. Click the
l.
button to stop the animation.
Select mesh_animation from the Animation Sequences list.
m. Click the play button.
n. Magnify the view as shown in Figure 24.7: The Mesh of the Displaced Flap (p. 932).
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Modeling Two-Way Fluid-Structure Interaction (FSI) Within Fluent
Figure 24.7: The Mesh of the Displaced Flap
o. Click the
button to stop the animation.
24.5. Summary
This tutorial demonstrated how to set up and solve a two-way intrinsic FSI simulation. You learned how
to enable a structural model and define the solid material, boundary conditions, and dynamic mesh
zones. After completing the simulation, you viewed animations of the resulting fluid velocity contours
and displacement of the structure. For more information about intrinsic FSI simulations, see the Fluent
User's Guide.
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Chapter 25: Using the Adjoint Solver – 2D Laminar
Flow Past a Cylinder
This tutorial is divided into the following sections:
25.1. Introduction
25.2. Problem Description
25.3. Setup and Solution
25.4. Summary
25.1. Introduction
ANSYS Fluent’s adjoint solver is used to compute the sensitivity of quantities of interest in a fluid system
with respect to the user-specified inputs, for an existing flow solution. Importantly, this also includes
the sensitivity of the computed results with respect to the geometric shape of the system. The adjoint
design change tool is a powerful component that can use the sensitivity information from one or more
adjoint solutions to guide systematic changes that result in predictable improvements in the system
performance, which can be made subject to various types of design constraints if desired.
This tutorial provides an example of how to generate sensitivity data for flow past a circular cylinder,
how to postprocess the results, and how to use the data to perform a multi-objective design change
that reduces drag and increases lift by morphing the mesh. The tutorial makes use of a previously
computed flow solution, and demonstrates how to do the following:
• Select the observable of interest.
• Access the solver controls for advancing the adjoint solution.
• Set convergence criteria and plot and print residuals.
• Advance the adjoint solver.
• Postprocess the results to extract sensitivity data.
• Use the design change tool to modify the cylinder shape to simultaneously reduce the drag and increase the lift.
25.2. Problem Description
The configuration is a circular cylinder, bounded above and below by symmetry planes. The flow is
laminar and incompressible with a Reynolds number of 40, based on the cylinder diameter. At this
Reynolds number, the flow is steady.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
25.3. Setup and Solution
The following sections describe the setup steps for this tutorial:
25.3.1. Step 1: Preparation
25.3.2. Step 2: Define Observables
25.3.3. Step 3: Compute the Drag Sensitivity
25.3.4. Step 4: Postprocess and Export Drag Sensitivity
25.3.5. Step 5: Compute Lift Sensitivity
25.3.6. Step 6: Modify the Shape
25.3.1. Step 1: Preparation
1.
Download the adjoint_cylinder.zip file here.
2.
Unzip adjoint_cylinder.zip to your working directory.
The files cylinder_tutorial.cas and cylinder_tutorial.dat can be found in the
folder .
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 2D under Dimension.
6.
Enable Double Precision under Options.
7.
Load the converged case and data file for the cylinder geometry.
File → Read → Case & Data...
When prompted, browse to the location of the case and data files and select cylinder_tutorial.cas to load. The corresponding data file will automatically be loaded as well.
Note:
After you read in the mesh, it will be displayed in the embedded graphics windows,
since you enabled the appropriate display option in Fluent Launcher.
The data file contains a previously computed flow solution that will serve as the starting point
for the adjoint calculation. Part of the mesh and the velocity field are shown below:
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Setup and Solution
Figure 25.1: Mesh Close to the Cylinder Surface
Figure 25.2: Contours of Velocity Magnitude
25.3.2. Step 2: Define Observables
Begin setting up the adjoint solver by opening the Adjoint Observables dialog box. Here you will
create lift and drag observables. Clicking on any button in the Gradient-Based group of the Design
ribbon tab will activate the adjoint solver.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Design → Gradient-Based → Observable...
Figure 25.3: Adjoint Observables Dialog Box
1. Click the Manage... button to open the Manage Adjoint Observables dialog box.
Figure 25.4: Manage Adjoint Observables Dialog Box
2. Click the Create... button in the Manage Adjoint Observables dialog box to open the Create
New Observable dialog box.
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Setup and Solution
Figure 25.5: Create New Observable Dialog Box
3. In the Create New Observable dialog box:
a. Ensure that Observable types is selected.
b. Select force from the selection list.
c. Enter force-drag for Name.
d. Click OK to close the dialog box.
4. In the Manage Adjoint Observables dialog box, the newly created force-drag observable appears
and must now be configured. (Figure 25.6: Manage Observables Dialog Box (p. 938)):
a. Select force-drag in the Observables list.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Figure 25.6: Manage Observables Dialog Box
b. Select wall under Wall Zones. This is the cylinder wall on which you want the force to
be evaluated.
c. Ensure that the X-Component direction is set to 1 and the Y-Component direction is set
to 0.
d. Click Apply to commit the settings for force-drag.
5. Repeat the process in the Manage Adjoint Observables dialog box to create a lift observable
with the following settings:
938
Name
force-lift
Wall Zones
wall
X-Component
0
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Setup and Solution
Y-Component
1
Tip:
If the Name field is not available in the Create New Observable dialog box, select
a different observable type and then select force again to make it available.
When you have configured the force-lift observable, click OK to commit the settings for forcelift and close the Manage Adjoint Observables dialog box.
25.3.3. Step 3: Compute the Drag Sensitivity
1. In the Adjoint Observables dialog box (Figure 25.7: Adjoint Observables Dialog Box (p. 939)) specify
that you will solve for the drag sensitivity.
Figure 25.7: Adjoint Observables Dialog Box
a. Select force-drag in the list of Observable Names.
The selection in the Adjoint Obervables dialog box determines the observable for which
sensitivities will be computed. You will first compute the drag sensitivities.
b. Select Minimize from the Sensitivity Orientation list, because you are trying to reduce
the drag force. This indicates that postprocessed results for the drag sensitivity will be
displayed such that a reduction in drag is achieved by a design change in the positive
sensitivity direction.
c. Click Evaluate to print the value of the drag force on the wall in the console.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Observable name: force-drag
Observable Value [N] = 1271.7444
This value is in SI units, with N denoting Newtons.
d. Close the Adjoint Observables dialog box.
2. Adjust the solution controls.
The default solution control settings are chosen to provide robust solution advancement for a
wide variety of problems, including those having complex geometry, high local flow rates, and
turbulence. Given sufficient iterations, a converged result can often be obtained without modifying
the controls.
For this simple laminar flow case, more aggressive settings will yield faster convergence.
Open the Adjoint Solution Controls dialog box (Figure 25.8: Adjoint Solution Controls Dialog
Box (p. 940)).
Design → Gradient-Based → Solver Controls...
Figure 25.8: Adjoint Solution Controls Dialog Box
a. Disable the Auto-Adjust Controls option.
This prevents Fluent from automatically choosing and adjusting the solution controls for you.
b. Enable Show Advancement Controls.
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Setup and Solution
c. Ensure that the Apply Preconditioning option is enabled.
Preconditioning can help the calculation progress in a stable manner.
d. Enter 100 for Courant Number.
Higher Courant Number values correspond to more aggressive settings / faster convergence,
which is appropriate for a simple case such as this.
e. Enter 0.05 for Artificial Compressibility.
f.
Click OK to close the dialog box.
3. Configure the adjoint solution monitors by opening the Adjoint Residual Monitors dialog box
(Figure 25.9: Adjoint Residual Monitors Dialog Box (p. 942)).
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Design → Gradient-Based → Monitors...
Figure 25.9: Adjoint Residual Monitors Dialog Box
In the Adjoint Residual Monitors dialog box, you set the adjoint equations that will be checked
for convergence, as well as set the corresponding convergence criteria.
a. Make sure that the Print to Console and Plot options are enabled.
b. Enter values of 1e-05 for Adjoint continuity and Adjoint velocity, and keep the default
value of 0.001 for Adjoint local flow rate. These settings are adequate for most cases. Make
sure that the Check Convergence options are enabled.
c. Click OK to close the dialog box.
4. Run the adjoint solver using the Run Adjoint Calculation dialog box (Figure 25.10: Run Adjoint
Calculation Dialog Box (p. 942)).
Design → Gradient-Based → Calculate...
Figure 25.10: Run Adjoint Calculation Dialog Box
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Setup and Solution
a. Click the Initialize button. This initializes the adjoint solution everywhere in the problem domain
to zero.
b. Set the Number of Iterations to 200. The adjoint solver is fully configured to start running
for this problem.
c. Click the Calculate button to advance the solver to convergence.
Figure 25.11: Residuals for the Converged Solution
d. When the calculation is complete, Close the Run Adjoint Calculation dialog box.
25.3.4. Step 4: Postprocess and Export Drag Sensitivity
In this section, postprocessing options for the adjoint solution are presented.
25.3.4.1. Boundary Condition Sensitivity
1. Open the Adjoint Reporting dialog box (Figure 25.12: Adjoint Reporting Dialog Box (p. 944)).
Design → Gradient-Based → Reporting...
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Figure 25.12: Adjoint Reporting Dialog Box
2. Select inlet under Boundary Choice and click the Report button to display a report in the
console of the available scalar sensitivity data on the inlet:
Updating shape sensitivity data.
Done.
Boundary condition sensitivity report: inlet
Observable: force-drag
Velocity Magnitude [m/s]: 40 Sensitivity ([N]/[m/s]): 54.55629
Decrease Velocity Magnitude to decrease force-drag
3. Close the Adjoint Reporting dialog box.
25.3.4.2. Momentum Source Sensitivity
1. Open the Contours dialog box.
Results → Graphics → Contours → New...
2. Enter x-sensitivity-bf for the Countour Name.
3. Select Sensitivities... and Sensitivity to Body Force X-Component (Cell Values) from the
Contours of drop-down lists.
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Setup and Solution
Figure 25.13: Contours Dialog Box When Plotting Adjoint Fields
4. Click Compute and then Display to view the contours (Figure 25.14: Adjoint Sensitivity to Body
Force X-Component Contours (p. 946)) and then Close the Contours dialog box.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Figure 25.14: Adjoint Sensitivity to Body Force X-Component Contours
Figure 25.14: Adjoint Sensitivity to Body Force X-Component Contours (p. 946) shows how sensitive the drag on the cylinder is to the application of a body force in the -direction in the flow.
If a body force is applied directly upstream of the cylinder, for example, the disturbed flow is
incident on the cylinder and modifies the force that it experiences.
25.3.4.3. Shape Sensitivity
1. Open the Vectors dialog box (Figure 25.15: Vectors Dialog Box (p. 947))
Results → Graphics → Vectors → New...
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Setup and Solution
Figure 25.15: Vectors Dialog Box
2. Enter sensitivity-shape for theVector Name.
3. Select Sensitivity to Shape from the Vectors of drop-down list.
4. Select Sensitivities... and Sensitivity to Mass Sources (Cell Values) from the Color by
drop-down lists.
5. Select arrow from the Style selection list.
6. Enter 1e-8 for Scale.
7. Select wall from the Surfaces selection list.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
8. Click the Display button to view the vectors (Figure 25.16: Shape Sensitivity Colored by
Sensitivity to Mass Sources (Cell Values) (p. 948)) and then Close the Vectors dialog box.
Tip:
In order to display the vector plot in the graphics window, you may need to
click the Fit to Window button
.
Figure 25.16: Shape Sensitivity Colored by Sensitivity to Mass Sources (Cell Values)
This plot shows how sensitive the drag on the cylinder is to changes in the surface shape. The drag
is affected more significantly if the cylinder is deformed on the upstream rather than the downstream
side. Maximum effect is achieved by narrowing the cylinder in the cross-stream direction.
25.3.4.4. Exporting Drag Sensitivity Data
Before computing the sensitivity for the force-lift observable, you need to define the region that
will be subject to geometry morphing, and export the drag sensitivity data so it can be used later
in the multi-objective optimization.
1.
Open the Design Tool dialog box.
Design → Gradient-Based → Design Tool...
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Setup and Solution
Figure 25.17: The Design Tool Dialog Box
2.
In the Region tab, define the region that will be modified for the design change.
a.
Ensure that Cartesian is selected from the Region Geometry drop-down list.
b.
Click Get Bounds....
c.
Select wall in the Bounding Region Definition dialog box and click OK.
This will initialize the morphing region to the bounding box around the cylinder wall.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
d.
Click Update Region to update the view of the bounding box illustration in the graphics
window.
You can use the Mesh Display dialog box to also display the mesh, in order to review it prior
to morphing.
Results → Graphics → Mesh → new...
Click Save/Display and close the Mesh Display dialog box.
e.
Click Larger Region several times until the X and Y Limits are ±1.907349 m (Figure 25.18: Morphing Region Around Cylinder (p. 950)).
Figure 25.18: Morphing Region Around Cylinder
f.
950
In the Objectives tab, click Manage Data....
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Setup and Solution
Figure 25.19: The Design Tool Dialog Box Objectives Tab
g.
In the Manage Sensitivity Data dialog box, click Export... and save the sensitivity data
as force-drag.s.
h.
Close the Design Tool dialog box.
25.3.5. Step 5: Compute Lift Sensitivity
1.
Select force-lift from the Observable Names selection list and select Maximize from the Sensitivity Orientation list in the Adjoint Observables dialog box.
Design → Gradient-Based → Observable...
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
2.
Initialize and Calculate the adjoint solution using the Run Adjoint Calculation dialog box to
obtain the sensitivities for the force-lift observable.
Design → Gradient-Based → Calculate...
Click Yes in the Question dialog box that appears to overwrite the existing adjoint solution data.
You can export the sensitivity data for the lift observable as you did for the drag, but it is not strictly
necessary if you plan to perform the multi-objective optimization in the current Fluent session.
25.3.6. Step 6: Modify the Shape
In this section, you will load the previously saved force-drag sensitivity data and perform the multiobjective design change.
1.
Open the Design Tool dialog box if it is not already open.
Design → Gradient-Based → Design Tool...
force-lift is now displayed in the Design Change tab because it is the currently selected observable. The Design Change tab functions as a dashboard for the design modification, where you
can select which boundaries are subject to modification, enable or disable conditions that you
have defined, specify relative weighting if you have multiple freeform objectives, and view predicted results. You will return to it to perform the design change after you have configured the
objectives and the morphing region.
2.
952
Retain the default selection of Polynomials from the Morphing Method list.
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Setup and Solution
This morphing method is appropriate when you prefer mesh quality over adherence to the design
conditions; otherwise the Direct Interpolation is recommended.
3.
Load the previously saved force-drag sensitivity data.
a.
Open the Objectives tab.
The force-lift observable is already listed because Include current data is enabled.
4.
b.
Click Manage Data... to open the Manage Sensitivity Data dialog box.
c.
Click Import... and select the force-drag.s file you created earlier. Click OK.
d.
Close the Manage Sensitivity Data dialog box.
Define the objective for each observable.
For this example, you will seek a design change that increases the lift and results in a 10% reduction in drag.
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
a.
In the Objectives tab, select the force-lift observable. The current value of the lift is displayed
along with options to specify the objective for the lift.
b.
Select Increase Value from the Objective list.
This indicates that you want to increase the lift, but are not prescribing a specific target change.
c.
Enter 100 for Target/Reference Change.
This setting is used to normalize the scale of the change in value of the observable, which can
be important in cases where multiple observables are considered that may be of different scales.
d.
Click Apply.
e.
Select force_drag.s in the list of observables.
f.
Select Target Change In Value from the Objective list.
This indicates that you are prescribing a specific change in the value of the observable, rather
than a freeform increase or decrease.
g.
954
Enter -10 for Target/Reference Change and enable the As Percentage option.
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Setup and Solution
10% is a generally a reasonable maximum target change for a design change. Using a target
change that is too large may result in very large deformations and/or overshooting the local
optimum.
h.
5.
Click Apply.
Configure the morphing region.
You already specified the dimensions of the region earlier when exporting the force-drag sensitivity. Now you will also configure the control-point density.
a.
Click the Region Conditions tab in the Design Tool dialog box.
b.
Enter 30 for Points in the In X Direction and In Y Direction group boxes.
c.
Click Apply.
You can use the Mesh Display dialog box to display the mesh, in order to see the increase in
control points.
Results → Graphics → Mesh → Edit...
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Many other settings are available in the Region Conditions tab, including constraints on controlpoint motion, symmetry conditions, and continuity conditions. For additional information, see
the section on defining region conditions in the Fluent User's Guide manual.
6.
Compute the design change and modify the mesh.
a.
Return to the Design Change tab.
b.
Select wall in the Zones To Be Modified selection list.
Only zones that are selected in the Zones To Be Modified list (or that have prescribed motions
applied) will be modified as part of the design change.
c.
If multiple freeform objectives were defined (that is, multiple objectives with Increase Value
or Decrease Value selected in the Objectives tab), you would need to specify the Weight
for each. In this case only one objective (force-lift) is freeform, so no input is required for
Weight.
d.
Retain the default settings of Control-Point Spacing for Freeform Scaling Scheme, and
0.1 for Freeform Scale Factor.
These settings allow you to adjust the magnitude of the attempted design change (Freeform
Scale Factor) and the basis for the scaling (Freeform Scaling Scheme).
e.
Click Calculate Design Change.
The Results list is updated to reflect the Expected change for each observable.
Note that the drag is predicted to decrease by 10% as you requested, and the lift is predicted
to increase.
956
f.
Click the Preview... button in the Mesh group box to preview the design change in the
graphics window.
g.
Select wall on the Preview Morphing dialog box and click Display.
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Setup and Solution
Figure 25.20: Morphing Preview of Cylinder
h.
Click the Modify button in the Mesh group box to apply the calculated mesh deformation
that will reposition the boundary and interior nodes of the mesh. Information regarding the
mesh modification is printed in the console:
Updating mesh (steady, mesh iteration = 00001, pseudo time step 1.0000e+00)...
Dynamic Mesh Statistics:
Minimum Volume
= 3.46267e-04
Maximum Volume
= 6.36270e-01
Maximum Cell Skew = 3.69247e-01 (cell zone 11)
Minimum Orthogonal Quality = 6.30753e-01 (cell zone 11)
i.
Display the new mesh geometry.
Results → Graphics → Mesh → mesh-1
Edit...
Click Save/Display and close the Mesh Display dialog box.
The effect on the mesh is shown in Figure 25.21: Mesh After Deformation (p. 958):
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Using the Adjoint Solver – 2D Laminar Flow Past a Cylinder
Figure 25.21: Mesh After Deformation
j.
Re-converge the conventional flow calculation for this new geometry in the Run Calculation
task page.
Solution → Run Calculation → Calculate
The currently loaded case file already has report definitions defined for lift and drag, or you
can Evaluate the new values in the Adjoint Observables dialog box.
Design → Gradient-Based → Observable...
The new values for drag and lift are reported to be:
Observable name: force-drag
Observable Value [N]: 1151.1748
Observable name: force-lift
Observable Value [N]: 122.87702
Note that the drag has changed by -120.57 N or -9.5% compared to the drag on the undeformed cylinder. This value compares very well with the change of -127.2 N (-10%) that was
predicted from the adjoint solver. The lift has increased by 122.4 N, which again compares
very well with the predicted change of 127.5 N.
7.
Save the case and data files (cylinder-adjoint.cas.h5 and cylinder-adjoint.dat.h5).
File → Write → Case & Data...
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Summary
25.4. Summary
This tutorial has demonstrated how to use the adjoint solver to compute the sensitivity of the drag and
lift on a circular cylinder to various inputs for a previously computed flow field. The process of setting
up and running the adjoint solver was illustrated. The steps to perform various forms of postprocessing
were also described. The design change tool was used to make a multi-objective change to the design
that reduced the drag and increased the lift in a predictable manner.
This example considered multiple objectives at a single flow condition. Another powerful application
of the design tool is to perform multi-objective design changes using sensitivities computed for multiple
flow conditions. This allows you to identify design changes that improve performance across a range
of anticipated operating conditions, potentially of differing importance. The design tool also offers a
rich set of additional capabilities for including prescribed deformations, bounding planes / surfaces,
and fixed-wall constraints in your multi-objective design change.
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959
960
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Chapter 26: Simulating a Single Battery Cell Using
the MSMD Battery Model
This tutorial is divided into the following sections:
26.1. Introduction
26.2. Prerequisites
26.3. Problem Description
26.4. Setup and Solution
26.5. Summary
26.6. Appendix
26.7. References
26.1. Introduction
This tutorial is used to show how to set up a battery cell simulation in ANSYS Fluent.
This tutorial demonstrates how to do the following:
• Set up a battery cell simulation using the NTGK battery submodel
• Perform the calculations for different battery discharge rates and compare the results using the
postprocessing capabilities of ANSYS Fluent
• Use the reduced order method (ROM) in a battery simulation
• Simulate a battery pulse discharge
• Introduce external and internal short-circuits in a battery simulation
26.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
26.3. Problem Description
The discharge behavior of a lithium-ion battery described in Kim’s paper [2] will be modeled in this
tutorial. You will use the NTGK model. The battery is a 14.6 Ah LiMn2O4 cathode/graphite anode battery.
The geometry of the battery cell is shown in Figure 26.1: Schematic of the Battery Cell Problem (p. 962).
You will study the battery’s behavior at different discharge rates.
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Figure 26.1: Schematic of the Battery Cell Problem
For external and internal short-circuit treatment, you will consider an extreme case where external and
internal short-circuits occur at the same time. You will simulate post-short-circuit battery processes. You
can assume that the internal short is caused by a nail penetration occurring near the center of the
battery.
26.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
26.4.1. Preparation
26.4.2. Reading and Scaling the Mesh
26.4.3. NTGK Battery Model Setup
26.4.4. Postprocessing
26.4.5. Simulating the Battery Pulse Discharge Using the ECM Model
26.4.6. Using the Reduced Order Method (ROM)
26.4.7. External and Internal Short-Circuit Treatment
26.4.1. Preparation
1.
Download the battery_cell.zip file here.
2.
Unzip battery_cell.zip to your working directory.
The mesh file unit_battery.msh can be found in the folder.
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Setup and Solution
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
26.4.2. Reading and Scaling the Mesh
1. Read the mesh file unit_battery.msh.
File → Read → Mesh...
When prompted, browse to the location of the unit_battery.msh and select the file.
Once you read in the mesh, it is displayed in the embedded graphics windows.
The geometry is already in the correct scale. You don’t need to scale it.
2. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
26.4.3. NTGK Battery Model Setup
The following sections describe the setup steps for this tutorial:
26.4.3.1. Specifying Solver and Models
26.4.3.2. Defining New Materials for Cell and Tabs
26.4.3.3. Defining Cell Zone Conditions
26.4.3.4. Defining Boundary Conditions
26.4.3.5. Specifying Solution Settings
26.4.3.6. Obtaining Solution
26.4.3.1. Specifying Solver and Models
1. In the Solver group of the General task page, enable a time-dependent calculation.
Setup →
General → Transient
2. Enable the battery model.
Physics → Models → More → Battery Model
a. In the Battery Model dialog box, select Enable Battery Model.
The dialog box expands to display the battery model’s settings.
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Simulating a Single Battery Cell Using the MSMD Battery Model
Figure 26.2: Model Options
Once you enable the battery model, the Energy equation will be automatically enabled in
order to solve for the temperature field.
b. Under the Model Options tab (Figure 26.2: Model Options (p. 964)), configure the following
battery operation conditions:
i.
Ensure that MSMD is selected for Solution Method.
ii. Under E-Chemistry Models, retain the default selection of NTGK Empirical Model.
iii. Under Electrical Parameters, retain the default value of 14.6 Ah for Nominal Cell
Capacity.
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Setup and Solution
iv. Select Enable Joule heat in active zones in the Energy Source Options group.
v. Retain the default selection of Specified C-Rate and the value of 1 for C-Rate.
vi. Retain the default value of 3 V for Min. Stop Voltage.
c. Under the Conductive Zones tab (Figure 26.3: Conductive Zones (p. 965)), configure the following settings:
Group
Control or List
Value or Selection
Active Components
Zone (s)
e-zone
Passive Components
Zone (s)
tab_nzone
tab_pzone
For this single cell case, there are no busbar zones. Electro-chemical reactions occur only in
the active zone. Battery tabs are usually modeled as passive zones, in which the potential
field is also solved.
Figure 26.3: Conductive Zones
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Simulating a Single Battery Cell Using the MSMD Battery Model
d. Under the Electric Contacts tab (Figure 26.4: Electric Contacts (p. 966)), configure the contact
surface and external connector settings as follows:
Group
External Connectors
Control or List
Value or Selection
Negative Tab
tab_n
Positive Tab
tab_p
The corresponding current or voltage boundary condition will be applied to those boundaries
automatically.
Under the Electric Contacts tab, you can also define extra contact resistance for each zone.
Figure 26.4: Electric Contacts
e. Click the Print Battery System Connection Information button.
ANSYS Fluent prints the battery connection information in the console window:
Battery Network Zone Information:
-------------------------------------
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Setup and Solution
Battery Serial 1
Parallel 1
Active zone: e_zone
----------------------------------Passive zone 0:
tab_nzone
Passive zone 1:
tab_pzone
Number of battery series stages =1; Number of batteries in parallel per series stage=1
****************END OF BATTERY CONNECTION INFO**************
f.
Verify that the connection information is correct.
g. Under the Model Parameters tab, retain the default settings for Y and U coefficients.
Note:
• If in your case, Y and U functions are not in the same function form as in Kim’s
paper, you need to modify the cae_user.c source code file.
• For a given battery, you can perform a set of constant current discharging tests,
and then use the battery's parameter estimation tool to obtain the Y and U
functions.
h. Click OK to close the Battery Model dialog box.
In the background, Fluent automatically hooks all the necessary UDFs for the problem.
i.
Click OK to close the Information dialog box.
26.4.3.2. Defining New Materials for Cell and Tabs
Define the new e_material material for the battery’s cell, p_material for the positive tab, and
n_material for the negative tab.
In the battery model, two transport equations are solved for the positive and negative potentials,
respectively. To specify the electric conductivity of the active material you need to define the two
electric conductivities, one for each potential field..
1. Create the electric material.
Physics → Materials → Create/Edit...
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Simulating a Single Battery Cell Using the MSMD Battery Model
a. In the Create/Edit Materials dialog box, select solid from the Material Type drop-down
list.
b. Enter e_material for Name and e for Chemical Formula.
c. Under Properties, set Density to 2092 [kg/m3].
d. Set Cp (Specific Heat) to 678 [J/kg-K].
e. Set Thermal Conductivity to 18.2 [W/m-K].
f.
Select defined-per-uds from the Electrical Conductivity drop-down list.
g. In the UDS Diffusion Coefficients dialog box, specify the user-defined scalars.
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Setup and Solution
i.
Select uds-0 in the User-Defined Scalar Diffusion list.
ii. Retain constant from the Coefficient drop-down list.
iii. Set Coefficient to 1.19e6.
iv. In a similar way, set uds-1 to 9.83e5 and click OK to close the UDS Diffusion
Coefficients dialog box.
v. In the Question dialog box, click No to retain aluminum and add the new material
(e_material) to the materials list.
Note:
Refer to Appendix (p. 1000) for information on how to calculate the battery
cell property values.
2. Create a new material for the positive tab by modifying copper from the solid material database.
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Simulating a Single Battery Cell Using the MSMD Battery Model
a. In the Create/Edit Materials dialog box, click Fluent Database....
b. In the Fluent Database Materials dialog box, make sure that solid is selected for Material
Type.
c. Select copper from Fluent Solids Materials and click Copy and then Close.
The Create/Edit Materials dialog box now displays the copied properties for copper.
d. Enter p_material for Name and pmat for Chemical Formula.
e. Ensure constant is selected for Electrical Conductivity and enter 1.0e7.
f.
Click Change/Create.
g. In the Question dialog box, click Yes to overwrite copper.
The new material (p_material) appears under Materials.
3. Create a new material for the negative tab with the same properties as the material for the
positive tab.
Note:
You do not need to create two different materials for the positive and negative tabs
if the positive and negative tabs are made of the same material. In this tutorial, the
two different tab materials with the same physical properties have been created for
demonstration purposes only.
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Setup and Solution
a. From Fluent Solid Materials drop-down list, select p_material.
b. Enter n_material for Name and nmat for Chemical Formula.
c. Click Change/Create.
d. In the Question dialog box, click No to retain p_material and add the new material (n_material) to the materials list.
e. Close the Create/Edit Materials dialog box.
26.4.3.3. Defining Cell Zone Conditions
Assign e_material to the cell zone, p_material to the positive tab and n_material to the negative
tab.
1. Assign e_material to the e_zone zone.
Setup →
Cell Zone Conditions →
e_zone → Edit...
a. In the Solid dialog box, select e_material from the Material Name drop-down list.
b. Click Apply.
2. In a similar manner, assign p_material to tab_pzone and n_material to tab_nzone.
26.4.3.4. Defining Boundary Conditions
Define the thermal boundary conditions for all walls for the cell, and positive and negative tabs.
1. Set the convection boundary condition for wall_active.
Setup →
Boundary Conditions → Wall
wall_active → Edit...
a. In the Wall dialog box, under the Thermal tab, under Thermal Conditions, enable
Convection.
b. Set Heat Transfer Coefficient to 5 [w/m2K].
c. Retain the default value of 300 [K] for Free Stream Temperature.
d. Click Apply and close the Wall dialog box.
You do not need to change the settings under the UDS tab since the boundary conditions for the two UDS scalars have been set automatically when you defined the cell
zone conditions.
2. Copy the boundary conditions for wall_active to wall_p and wall_n.
Setup →
Boundary Conditions → wall_active
Copy...
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Simulating a Single Battery Cell Using the MSMD Battery Model
a. Make sure that wall_active is selected in the From Boundary Zone list.
b. Select wall_n and wall_p in the To Boundary Zone list.
c. Click Copy, click OK in the confirmation prompt, and close the Copy Conditions dialog
box.
26.4.3.5. Specifying Solution Settings
1. Turn off the flow and turbulence equations.
Solution → Controls → Equations...
a. In the Equations dialog box, deselect Flow and Turbulence from the Equation selection
list.
b. Click OK.
2. Remove the convergence criteria to ensure that automatic convergence checking does not occur.
Solution → Reports → Residuals...
a. In the Residual Monitors dialog box, enable Show Advanced Options.
b. Select none from the Convergence Criterion drop-down list.
c. Click OK.
3. Create a surface report definition for the voltage at the positive tab.
Solution → Reports → Definitions → New → Surface Report → Area-Weighted Average
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Setup and Solution
a. In the Surface Report Definition dialog box, enter voltage_vp for Name.
b. Select Battery Variables... and Passive Zone Potential from the Field Variable drop-down
lists.
c. From the Surfaces selection list, select tab_p.
d. In the Create group box, enable Report File, Report Plot and Print to Console.
e. Click OK to save the voltage_vp report definition and close the Surface Report Definition
dialog box.
f.
Rename the report output file.
Solution → Monitors → Report Files → voltage_vp-rfile
Edit...
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Simulating a Single Battery Cell Using the MSMD Battery Model
i.
Enter ntgk-1c.out for File Name.
ii. Click OK to close the Edit Report File dialog box.
g. Modify the attributes of the plot axes.
Solution → Monitors → Report Plots → voltage_vp-rplot
i.
Edit...
In the Edit Report Plot dialog box, under the Plot Window group box, click the Axes...
button to open the Axes dialog box.
ii. Select the X axis and set Precision to 0.
iii. Click Apply.
iv. Select the Y axis and set Precision to 2.
v. Click Apply and close the Axes dialog box.
Note:
You must click Apply to save the modified settings for each axis.
vi. Make sure that time-step is selected from the Get Data Every drop-down list.
vii. Click OK to close the Edit Report Plot dialog box.
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Setup and Solution
4. Create a volume report definition for the maximum temperature in the domain.
Solution → Reports → Definitions → New → Volume Report → Max...
a. In the Volume Report Definition dialog box, enter max_temp for Name.
b. Select Temperature... and Static Temperature from the Field Variable drop-down lists.
c. From the Cell Zones selection list, select all zones.
d. In the Create group box, enable Report File, Report Plot and Print to Console.
e. Click OK to save the volume report definition settings and close the Volume Report
Definition dialog box.
f.
Rename the report output file.
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Simulating a Single Battery Cell Using the MSMD Battery Model
Solution → Monitors → Report Files → max_temp-rfile
i.
Edit...
Enter max-temp-1c.out for Output File Base Name.
ii. Click OK to close the Edit Report File dialog box.
g. Modify the axis attributes by setting the Precision to 0 for the X axis and to 2 for the Y
axes (in a manner similar to the surface plot definition).
h. Click OK.
5. Save the case file (unit_battery.cas.h5).
File → Write → Case...
26.4.3.6. Obtaining Solution
1. Initialize the field variables using the Standard Initialization method.
Solution → Initialization
a. Retain the selection of the Standard method (Initialization group).
b. Click Initialize.
You do not need to modify Initial Values in the Solution Initialization task page, because
these values are not used for initialization. The ANSYS Fluent solver automatically computes
the initial condition for UDS0 and UDS1.
Note:
Warning messages are printed in the Fluent console informing you about interior
zones between different solids. Such messages appear when two adjacent solid zones
separated by an interior face type are using two different materials. The message
suggests using the mesh/modify-zones/slit-interior-between-diff-solids text command
to slit the interior zone between solid zones of differing materials to create a wall/wallshadow interfaces. In general, the material property interpolation at wall/wall-shadow
is more accurate if different materials are used at two sides of an interface. However,
the battery model is implemented in such a way that both treatments are equivalent,
and such messages could be ignored.
2. Run the simulation.
Solution → Run Calculation
a. Set Time Step Size to 30 seconds and No. of Time Steps to 100.
b. Click Calculate.
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Setup and Solution
The residual plot, the report for voltage at the positive tab and the history of the maximum
temperature in the domain are shown in Figure 26.5: Residual History of the Simulation (p. 977),
Figure 26.6: Report Plot of Discharge Curve at 1 C (p. 977), and Figure 26.7: History of Maximum
Temperature in the Domain (p. 978), respectively.
Figure 26.5: Residual History of the Simulation
Figure 26.6: Report Plot of Discharge Curve at 1 C
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Simulating a Single Battery Cell Using the MSMD Battery Model
Figure 26.7: History of Maximum Temperature in the Domain
3. Save the case and data files (unit_battery.cas.h5 and unit_battery.dat.h5).
File → Write → Case & Data...
26.4.4. Postprocessing
In this section, postprocessing capabilities for the MSMD battery model solution are demonstrated.
1. Display the contour plot of the phase potential for the positive electrode.
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-phi+ for Contour Name.
b. Select Banded in the Coloring group box.
c. From the Contours of drop-down list, select Battery Variables... and Cathode Potential.
d. Click the Toggle Tree View button next to the Surfaces filter and from the drop-down list,
select Surface Type (under Group by).
e. From the Surfaces selection list, under Wall, select wall_active.
f.
Click Save/Display and close the Contours dialog box.
Note:
To change the precision for the colormap labels, click Colormap Options... to open
the Colormap dialog box, and increase the value of Precision.
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Figure 26.8: Contour Plot of Phase Potential for the Positive Electrode
2. In a similar manner, display the contour plot of the phase potential for the negative electrode.
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-phi- for Contour Name.
b. Select Banded in the Coloring group box.
c. From the Contours of drop-down list, select Battery Variables... and Anode Potential.
d. From the Surfaces selection list, select wall_active.
e. Click Save/Display and close the Contours dialog box.
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Figure 26.9: Contour Plot of Phase Potential for the Negative Electrode
3. Display a contour plot of the phase potential in the passive zones
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-phi-passive for Contour Name.
b. Select Banded in the Coloring group box.
c. From the Contours of drop-down list, select User Battery Variables... and Passive Zone
Potential.
d. From the Surfaces selection list, select tab_n, tab_p, wall_n, and wall_p.
e. Click Save/Display and close the Contours dialog box.
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Figure 26.10: Contour Plot of Phase Potential for Passive Zones
4. Display the contour plot of the temperature.
Results → Graphics → Contours → New...
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Setup and Solution
a. Enter contour-temp for Contour Name.
b. Select Banded in the Coloring group box.
c. From the Contours of drop-down list, select Temperature... and Static Temperature.
d. Select Wall in the Surfaces selection list.
The surfaces listed under Wall are automatically selected in the Surfaces list.
e. Click Save/Display and close the Contours dialog box.
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Simulating a Single Battery Cell Using the MSMD Battery Model
Figure 26.11: Contour Plot of Temperature
5. Display the vector plot of current density.
Results → Graphics → Vectors → New...
986
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Setup and Solution
a. Enter vector-current-dens for Vector Name.
b. Select arrow from the Style drop-down list.
c. In the Vectors dialog box, select current-density-j from the Vectors of drop-down list.
d. Select Battery Variables... and Current Magnitude from the Color by drop-down list.
e. Click the Toggle Tree View button next to the Surfaces filter and from the drop-down list,
select Surface Type (under Group by).
f.
From the Surfaces selection list, select Wall.
g. In the Options group, enable Draw Mesh and in the Mesh Display dialog box, set the mesh
display options as desired.
h. Click Save/Display and close the Vectors dialog box.
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Simulating a Single Battery Cell Using the MSMD Battery Model
Figure 26.12: Vector Plot of Current Density
6. Save the case file as ntgk.cas.h5. You will use this saved case later to treat electric short-circuits.
7. Repeat the simulation for the following charge rates and time steps:
C-Rate
Number of Time Steps
0.5 C
230
5C
23
Make the following changes in the model’s settings:
Setup → Models → Battery Model
Edit...
a. In the Battery Model dialog box, under the Model Options tab, specify the value listed in
the above table for the C-Rate.
b. Modify the output filename for the voltage_vp-rfile report file by entering ntgk-C-Rate.out
for Output File Base Name in the corresponding Edit Report File dialog box, where C-Rate
is the value of the battery discharge rate. (For example, for C-Rate = 0.5 C, you will enter ntgk0.5c.out for the filename).
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Setup and Solution
c. Similarly, modify the output filename for max_temp-rfile by entering max-temp-C-Rate.out
for Output File Base Name in the corresponding Edit Report File dialog box.
d. Initialize and run the solution for the number of the times steps specified in the above table.
Note:
The Fluent solver will stop either after completing the specified number of time
steps or when the Min. Stop Voltage condition is reached.
8. Display the discharge curves for the positive tab for the different discharge rates.
a. Open the Plot Data Sources dialog box.
Results → Plots → Data Sources...
b. Click Load File... to open the Select File dialog box.
c. Change the Files of type: drop-down filter to All Files (*), select ntgk-0.5c.out and click
OK.
d. Deselect flow-time from the Y Axis Variables selection list.
e. Select voltage_vp in the Legend Names group box, enter 0.5c in the text box that populates
below it and click Change Legend Entry.
f.
Do the same for ntgk-1c.out and ntgk-5c.out and change their legend entries accordingly.
g. Enter Discharge Rate for the Legend Label in the Plot group box.
h. Click Plot and close the Plot Data Sources dialog box.
Note:
Use the Axes dialog box to set the precision for the plot axes.
The Figure 26.13: NTGK Model: Discharge Curves (p. 990) shows the discharge curves for different
discharge rates in the function of time.
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Simulating a Single Battery Cell Using the MSMD Battery Model
Figure 26.13: NTGK Model: Discharge Curves
9. In a manner similar to the previous step, load the files max-temp-0.5c.out, max-temp1c.out, and max-temp-5c.out and display the maximum temperature curves in the domain.
Figure 26.14: NTGK Model: Maximum Temperature in the Domain (p. 990) shows the maximum
temperature curves in the simulation for different discharge rates.
Figure 26.14: NTGK Model: Maximum Temperature in the Domain
990
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Setup and Solution
26.4.5. Simulating the Battery Pulse Discharge Using the ECM Model
Setup → Models → Battery Model
Edit...
1. In the Battery Model dialog box, under E-Chemistry Models, select Equivalent Circuit Model.
2. Under Electrical Parameters, retain the default value of 14.6 Ah for Nominal Cell Capacity.
3. Retain the default selection of Specified C-Rate and enter 1 for C-Rate.
4. Under the Model Parameters tab, retain the battery specific parameters.
For a given battery, these model parameters can be obtained using the battery's HPPC testing
data.
5. Click OK to apply the ECM battery model settings and close the Battery Model dialog box
6. Click OK in the Warning dialog box informing you that the re-initialization of the battery model
is required.
7. In the Solution Initialization task page, click Initialize to re-initialize the field variables.
8. Simulate the battery pulse discharge by changing the battery operating conditions each time
after running the calculation for five minutes.
a. In the Run Calculation task page, make sure that Time Step Size is set to 30, set Number of
Time Steps to 10 and click Calculate.
b. Click Yes to create new report definition files.
c. Once the calculation is complete, set C-Rate in the MSMD Battery Model dialog box to 0 and
run the calculation for 10 more time steps.
d. Continue the simulation by alternating the value of C-Rate between 1 C and 0 C until, until
the battery is fully discharged.
Note:
Instead of doing this manually, you can use the Using Profile option in the MSMD
Battery Model dialog box and load a profile file with specified C-rate fluctuations
to drive the whole process. For more information about the usage of a profile file,
refer to Specifying Battery Model Options in the ANSYS Fluent User's Guide.
The battery pulse discharge is summarized in Figure 26.15: Battery Pulse Discharge (p. 992).
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Simulating a Single Battery Cell Using the MSMD Battery Model
Figure 26.15: Battery Pulse Discharge
26.4.6. Using the Reduced Order Method (ROM)
You will use the ntgk.cas.h5 case file that you saved earlier to illustrate how to use the ROM for
time-efficient calculations. This section assumes that you are already familiar with the ANSYS Fluent
battery model; only the steps related specifically to using the ROM for problem solution are discussed
here.
1. Read the NTGK model case file ntgk.cas.h5.
2. Initialize the problem.
3. In the Run Calculation task page, make sure that Time Step Size is set to 30, set Number of
Time Steps to 3 and click Calculate.
Click No in the Question dialog box when asked if you would like to append the new data to the
existing file, and then click Yes in the Warning dialog box to overwrite the existing file.
4. Once the calculation is complete, enable the ROM.
Setup → Models → Battery Model
Edit...
a. In the MSMD Method Option group box, select Reduced Order Method.
b. Set Number of Sub-Steps/Time Step to 10 and click OK to close the Battery Model dialog
box.
5. Re-run the simulation continuing from step 2 in Obtaining Solution (p. 976).
The solution of the simulation using the ROM is significantly faster than when using the direct
method without any changes in results.
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Setup and Solution
26.4.7. External and Internal Short-Circuit Treatment
You will again use the ntgk.cas.h5 case file that you saved earlier to illustrate how to treat external
and internal short-circuits in a battery simulation. It is assumed that the battery is experiencing external and internal short-circuit simultaneously. This extreme case will be used to demonstrate the
problem setup and postprocessing in a short simulation. This section assumes that you are already
familiar with the ANSYS Fluent battery model, only the steps related to short simulation are emphasized
here.
26.4.7.1. Setting up and Solving a Short-Circuit Problem
1. Read the NTGK model case file ntgk.cas.h5.
2. Set up the external electric short-circuit.
Setup → Models → Battery Model
Edit...
a. In the Battery Model dialog box, under the Model Options tab, in the Solution Options
group box, enable Specified Resistance.
b. For External Resistance, enter 0.5 Ohm and click OK.
3. Set up the internal electric short-circuit in the center of the battery cell.
a. Mark the short-circuit zone shown in Figure 26.16: Internal Short Circuit Region Marked for
Patching (p. 993) using the region adaption feature.
Solution → Cell Registers
New → Region...
Figure 26.16: Internal Short Circuit Region Marked for Patching
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Simulating a Single Battery Cell Using the MSMD Battery Model
i.
In the Region Register dialog box, enter the following values for Input Coordinates.
X Min
X Max
Y Min
Y Max
Z Min
Z Max
-0.01
0.01
-0.01
0.02
-1
1
ii. Click Save/Display and close the Region Register dialog box.
Fluent reports in the console that 12 cells were marked for refinement.
4. Initialize the field variables using the standard initialization method.
Solution → Initialization → Initialize
5. Patch the internal short circuit zone with the short resistance value.
Solution → Initialization → Patch...
a. In the Patch dialog box, select Battery Short Resistance under Variable.
b. Select region_0 under Registers to Patch.
c. For Value, enter 5.0e-7.
d. Click Patch and close the Patch dialog box.
6. Save the case file (ntgk_short_circuit.cas.h5).
File → Write → Case...
7. Run the simulation for 5 seconds.
Solution → Run Calculation
a. Set Time Step Size to 1 second and No. of Time Steps to 5.
b. Click Calculate.
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Setup and Solution
8. Save the case and data files (ntgk_short_circuit.cas.h5 and ntgk_short_circuit.dat.h5).
File → Write → Case & Data...
26.4.7.2. Postprocessing
1. Compute the battery tab voltage
.
Results → Reports → Surface Integrals...
a. In the Surface Integrals dialog box, from the Report Type drop-down list, select AreaWeighted Average.
b. From the Field Variable drop-down lists, select Battery Variables... and Passive Zone Potential.
c. In the Surfaces filter, type t to display surface names that begin with "t" and select tab_p
from the selection list.
d. Click Compute and close the Surface Integrals dialog box.
The battery tab voltage of approximately 4.077 V is printed in the Area-Weighted Average
field and in the Fluent console.
2. Compute the battery tab current
.
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Simulating a Single Battery Cell Using the MSMD Battery Model
Results → Reports → Volume Integrals...
a. In the Report Type group box, select Volume Integrals.
b. From the Field Variable drop-down lists, select Battery Variables... and Total Current
Source.
c. From the Cell Zones selection list, select e_zone.
d. Click Compute and close the Volume Integrals dialog box.
Fluent reports in the Total Volume Integral field and in the console that the total volume
integral for the volumetric current source is approximately 8.155 A.
The computed values of the battery tab current and voltage satisfy the tab boundary condition
.
3. Display the vector plot of current at the positive and negative current collectors.
Results → Graphics → Vectors → New...
a. Enter vector-current+ for Vector Name.
b. Select arrow from the Style drop-down list.
c. In the Vectors dialog box, select current-density-jp from the Vectors of drop-down list.
d. Select Battery Variables... and Current Magnitude from the Color by drop-down lists.
e. From the Surfaces selection list, select Wall.
The surfaces of the "wall" type are automatically selected in the Surfaces list.
f.
Click Save/Display.
g. The plot shows the vector plot of electric current flow in the positive current collector of
the battery cell.
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Setup and Solution
Figure 26.17: The Vector Plots of Current at the Positive Current Collectors
h. In a similar manner, display the current for the negative current collector by selecting currentdensity-jn from the Vectors of drop-down list.
The plot shows the vector plots of electric current flow in the negative current collector of
the battery cell. These plots clearly show that besides providing tab current, short current
flows from positive electrode to the negative electrode through the short area.
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Simulating a Single Battery Cell Using the MSMD Battery Model
Figure 26.18: The Vector Plots of Current at the Negative Current Collectors
i.
Close the Vectors dialog box.
4. Display the contour plot of the temperature as you did previously.
Results → Graphics → Contours → contour-temp
998
Display
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Setup and Solution
a. Figure 26.19: Contour Plot of Temperature
Figure 26.19: Contour Plot of Temperature (p. 999) shows a temperature hotspot in the internal
shorted area of the battery cell.
5. Check for different electric current flow rates in the manner described in step 2.
Results → Reports → Volume Integrals...
a. Generate volume integral reports for the field variables listed in the table below.
Field Variable
Notation
Reported Value
Short Current Source
-15.843 A
ECHEM Current Source
23.999 A
b. Verify that the total produced electric current equals to the sum of tab and short current,
that is
.
6. Check for different types of heat generation rates.
a. As you did for the current source reports, generate reports for the field variables listed in
the table below.
Field Variable
Joule Heat Source
Notation
Reported Value
0.0339 W
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Simulating a Single Battery Cell Using the MSMD Battery Model
Field Variable
Notation
Reported Value
Echem Heat Source
1.092 W
Short-Circuit Heat Source
64.607 W
Total Heat Source
65.733 W
b. Verify that the total heat generation rate is the sum of different contributions, that is
.
7. Save the case file (ntgk_short_circuit.cas.h5).
File → Write → Case...
Note that, as battery's temperature increases, thermal runaway may occur. If thermal runaway starts,
some undesirable exothermic decomposition reactions will occur. For thermal runaway simulations,
the default electrochemistry model cannot be used. Short treatment can only capture the thermal
ramp-up process before the onset of thermal runaway.
26.5. Summary
In this tutorial, you studied how to solve a battery cell problem using the NTGK submodel with the
default settings. You then used the ROM to speed up the computation time of the battery model simulation. In addition, you learned how to use the MSMD model capability to treat external and internal
short-circuits.
For more information about using the Dual-Potential MSMD Battery model, see the ANSYS Fluent User's
and Theory Guides.
26.6. Appendix
The battery cell cross-section is shown in the figure below.
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Appendix
You can estimate the material properties for your battery cell using the following correlations:
• For density , heat capacity
, and thermal conductivity
:
where
is the effective property value of a material property (such as density, heat capacity, or
thermal conductivity), is the thickness. The subscripts , , and refer to current collector, electrode,
and separator, respectively. The superscripts and refer to positive and negative, respectively.
• For electric conductivity :
The material properties are taken from Kim’s papers [2] and [1]. The computed material properties for
the battery cell presented in the tutorial are shown in the table below.
Zone
Total
[um]
20
150
12
145
10
322
[kg/m3]
2700
1500
1200
2500
8960
2092
[J/kg-K]
900
700
700
700
385
678
[W/m-K]
238
5
1
5
398
18.2
[s/m]
3.83e7
13.9
100
6.33e7
= 1.19e6
= 9.83e5
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Simulating a Single Battery Cell Using the MSMD Battery Model
26.7. References
1. U. S. Kim et al, "Effect of electrode configuration on the thermal behavior of a lithium-polymer battery",
Journal of Power Sources, Volume 180 (2), pages 909-916, 2008.
2. U. S. Kim, et al., "Modeling the Dependence of the Discharge Behavior of a Lithium-Ion Battery on
the Environmental Temperature", J. of Electrochemical Soc., Volume 158 (5), pages A611-A618, 2011.
1002
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Chapter 27: Simulating a 1P3S Battery Pack Using the
Battery Model
This tutorial is divided into the following sections:
27.1. Introduction
27.2. Prerequisites
27.3. Problem Description
27.4. Setup and Solution
27.5. Summary
27.1. Introduction
This tutorial is used to show how to set up a battery pack (battery system connected in parallel/series
pattern) simulation in ANSYS Fluent. All the three submodels are available for a pack simulation.
This tutorial illustrates how to do the following:
• Set up a battery pack simulation using the NTGK battery submodel in ANSYS Fluent
• Define active, tab, and busbar conductive zones
• Define electric contacts for the contact surface and external connectors
• Define electric conductivity for the active material using the user-defined scalars
• Define electric conductivity for the passive material using the user-defined function
• Obtain the battery pack simulation results and perform postprocessing activities
Most problem setup procedures are similar to the single cell simulation. The differences in the problem
setup will be emphasized in this tutorial.
27.2. Prerequisites
This tutorial is written with the assumption that you have completed the introductory tutorials found
in this manual and that you are familiar with the ANSYS Fluent outline view and ribbon structure. Some
steps in the setup and solution procedure will not be shown explicitly.
27.3. Problem Description
This problem considers a small 1P3S battery pack, that is, the three battery cells connected in series. A
schematic of the problem is shown in Figure 27.1: Schematic of the Battery Pack Problem (p. 1004).
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Simulating a 1P3S Battery Pack Using the Battery Model
Figure 27.1: Schematic of the Battery Pack Problem
The discharging process of the battery pack is occurring under constant power of 200 W. The nominal
cell capacity is 14.6 Ah.
You will create a material for the battery cells (an active material) and define the electric conductivity
for the active material using the user-defined scalars (UDS). You will create a material for busbars and
tabs (a passive material) and define the electric conductivity for the passive material using the provided
user-defined function (UDF). You will use the same material for busbars and tabs.
In this tutorial, you will use the NTGK battery submodel to simulate the discharging process under
constant power conditions.
27.4. Setup and Solution
The following sections describe the setup and solution steps for this tutorial:
27.4.1. Preparation
27.4.2. Reading and Scaling the Mesh
27.4.3. Battery Model Setup
27.4.4. Postprocessing
27.4.1. Preparation
1.
Download the battery_pack.zip file here.
2.
Unzip battery_pack.zip to your working directory.
The mesh file 1P3S_battery_pack.msh can be found in the folder.
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Setup and Solution
3.
Use the Fluent Launcher to start ANSYS Fluent.
4.
Select Solution in the top-left selection list to start Fluent in Solution Mode.
5.
Select 3D under Dimension.
6.
Enable Double Precision under Options.
7.
Set Solver Processes to 1 under Parallel (Local Machine).
27.4.2. Reading and Scaling the Mesh
1. Read the mesh file 1P3S_battery_pack.msh.
File → Read → Mesh...
When prompted, browse to the location of the 1P3S_battery_pack.msh and select the file.
Once you read in the mesh, it is displayed in the embedded graphics windows.
2. Check the mesh.
Domain → Mesh → Check → Perform Mesh Check
3. Scale the mesh.
Domain → Mesh → Scale
a. In the Scale Mesh dialog box, select Specify Scaling Factors in the Scaling group.
b. Enter 0.1 for X, Y and Z in the Scaling Factors group.
c. Click Scale and close the Scale Mesh dialog box.
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Simulating a 1P3S Battery Pack Using the Battery Model
d. Right click in the graphics window and select Refresh Display
e. Click the Fit to Window icon,
, to fit and center the mesh in the graphics window.
4. Check the mesh.
Domain → Mesh → Perform Mesh Check
27.4.3. Battery Model Setup
The following sections describe the setup steps for this tutorial:
27.4.3.1. Specifying Solver and Models
27.4.3.2. Defining New Materials
27.4.3.3. Defining Cell Zone Conditions
27.4.3.4. Defining Boundary Conditions
27.4.3.5. Specifying Solution Settings
27.4.3.6. Obtaining Solution
27.4.3.1. Specifying Solver and Models
1. Enable a time-dependent calculation by selecting Transient in the General task page (Solver
group).
Setup →
General → Transient
2. Enable the battery model.
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Setup and Solution
Physics → Models → More → Battery Model
a. In the Battery Model dialog box, select Enable Battery Model.
The dialog box expands to display the battery model’s settings.
Figure 27.2: Model Options
Once you enable the battery model, the Energy equation will be automatically enabled in
order to solve for the temperature field.
b. Under the Model Options tab (Figure 27.2: Model Options (p. 1007)), configure the following
battery operation conditions:
i.
Under E-Chemistry Models, enable NTGK Empirical Model.
ii. In the Electrical Parameters group, retain the default value of 14.6 Ah for Nominal
Cell Capacity.
iii. Select Enable Joule heat in active zones in the Energy Source Options group.
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Simulating a 1P3S Battery Pack Using the Battery Model
iv. Enable Specified System Power in the Solution Options group and set System Power
to 200 W.
c. Under the Model Parameters tab, retain the default settings for Y and U coefficients.
d. Under the Conductive Zones tab (Figure 27.3: Conductive Zones (p. 1009)), configure the following settings:
Group
Control or List
Value or Selection
Active Components
Zone (s)
cell_1
cell_2
cell_3
Passive Components
Zone (s)
n_tabzone_1
n_tabzone_2
n_tabzone_3
p_tabzone_1
p_tabzone_2
p_tabzone_3
bar1
bar2
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Setup and Solution
Figure 27.3: Conductive Zones
e. Under the Electric Contacts tab (Figure 27.4: Electric Contacts (p. 1010)), configure the contact
surface and external connector settings as follows:
Group
Control or List
Value or Selection
External Connectors
Negative Tab
tab_n
Positive Tab
tab_p
The corresponding current or voltage boundary condition will be applied to those boundaries
automatically.
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Simulating a 1P3S Battery Pack Using the Battery Model
Figure 27.4: Electric Contacts
f.
Click the Print Battery System Connection Information button.
ANSYS Fluent prints the battery connection information in the console window:
Battery Network Zone Information:
------------------------------------Battery Serial 1
Parallel 1
Active zone: cell_1
Battery Serial 2
Parallel 1
Active zone: cell_2
Battery Serial 3
Parallel 1
Active zone: cell_3
----------------------------------Passive zone 0:
n_tabzone_1
Passive zone 1:
p_tabzone_1
bar1
n_tabzone_2
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Setup and Solution
Passive zone 2:
p_tabzone_2
bar2
n_tabzone_3
Passive zone 3:
p_tabzone_3
Number of battery series stages =3; Number of batteries in parallel per series stage=1
****************END OF BATTERY CONNECTION INFO**************
g. Verify that the connection information is correct. If an error message appears or if the connections are not what you want, redefine the conductive zones in the Conductive Zones
tab (Figure 27.3: Conductive Zones (p. 1009)). Repeat this process until you confirm that the
battery connections are set correctly.
Important:
To set a valid connection, you must connect the negative tab to the positive
tab through conductive zones.
h. Click OK to close the Battery Model dialog box.
In the background, Fluent automatically hooks all the necessary UDFs for the problem.
i.
Click OK to close the Information dialog box.
27.4.3.2. Defining New Materials
Define the new e_material material for all the battery’s cells and busbar_material material for the
battery pack’s busbars and tabs.
1. Create the electric material.
Setup → Materials → Solid → aluminum
Edit...
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Simulating a 1P3S Battery Pack Using the Battery Model
a. In the Create/Edit Materials dialog box, enter e_material for Name and e for Chemical
Formula.
b. Set Thermal Conductivity to 20.
c. Under Properties, ensure that defined-per-uds is selected from the Electrical Conductivity
drop-down list and click Edit... next to Electrical Conductivity.
d. In the UDS Diffusion Coefficients dialog box, set the constant value of 1.0 e6 for the both
user-defined scalars.
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Setup and Solution
i.
Select uds-0 in the User-Defined Scalar Diffusion list.
ii. Retain constant from the Coefficient drop-down list.
iii. Set 1.0 e6 [1/ohm-m] for Coefficient.
iv. In a similar way, set uds-1 to 1.0 e6 [1/ohm-m] and click OK to close the UDS
Diffusion Coefficients dialog box.
e. In the Question dialog box, click No to retain aluminum and add the new material (e_material) to the materials list.
f.
Ensure that e_material (e) is selected from the Fluent Solid Materials drop-down list.
g. Close the Create/Edit Material dialog box.
2. Create the busbar_material material for busbars and tabs by modifying e-material you have
created in the previous step.
Setup → Materials → Solid → e-material
Edit...
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As stated in the problem description, you will use the same material for busbars and tabs.
Note:
If the busbar and tab materials are different, you need to define the two different
materials and assign them to the busbars and tabs, respectively.
a. In the Create/Edit Materials dialog box, enter busbar_material for Name and bus for
Chemical Formula.
b. Set Thermal Conductivity to 20.
c. Enter a value of 3.541 e7 [1/ohm-m] for Electrical Conductivity.
d. Click Change/Create.
e. In the Question dialog box, click No to retain e_material and add the new material (busbar_material) to the materials list.
f.
Ensure that busbar_material (bus) is selected from the Fluent Solid Materials dropdown list.
g. Close the Create/Edit Materials dialog box.
27.4.3.3. Defining Cell Zone Conditions
Assign e_material to all the cell zones and busbar_material to all the tabs and busbars.
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Setup and Solution
1. Assign e_material to the cell_1 cell zone.
Setup →
Cell Zone Conditions →
cell_1 → Edit...
a. In the Solid dialog box, select e_material from the Material Name drop-down list.
b. Click Apply and close the Solid dialog box.
2. Copy the cell zone condition for the cell_1 zone to the cell_2 and cell_3 cell zones.
Setup →
Cell Zone Conditions →
cell_1 → Copy...
a. In the Copy Conditions dialog box, select cell_1 in the From Cell Zone list.
b. In the To Cell Zones list, select cell_2 and cell_3.
c. Click Copy.
d. Click OK in the Question dialog box to copy the cell zone conditions and close the Copy
Conditions dialog box.
3. In a similar manner, assign busbar_material to all the tabs and busbars cell zones.
27.4.3.4. Defining Boundary Conditions
Define the thermal boundary conditions for all walls for the cells, busbars, and tabs. The boundary
conditions for the two UDSs have been set automatically when you defined the cell zone conditions.
1. Set the convection boundary condition for wall-cell_1.
Physics → Zones → Boundaries
a. In the Boundary Conditions task page, select wall-cell_1 and click Edit....
b. In the Wall dialog box, under the Thermal tab, configure the following settings:
i.
Under Thermal Conditions, enable Convection.
ii. Set Heat Transfer Coefficient to 5 [w/m2K].
iii. Set Free Stream Temperature to 300 [K].
iv. Click Apply and close the Wall dialog box.
2. Copy the boundary conditions for wall-cell_1 to wall-cell_2, wall-cell_3 and all the tab
and busbar wall zones (all boundary zones that have names starting with the "wall" string
and containing the "bar" or "tabzone" string).
Setup →
Boundary Conditions →
wall-cell_1 → Copy...
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Simulating a 1P3S Battery Pack Using the Battery Model
27.4.3.5. Specifying Solution Settings
1. Turn off the flow and turbulence equations.
Solution → Controls → Equations...
a. In the Equations dialog box, deselect Flow and Turbulence from the Equation selection
list.
b. Click OK.
2. Remove the convergence criteria to ensure that automatic convergence checking does not occur.
Solution → Reports → Residuals...
a. In the Residual Monitors dialog box, enable Show Advanced Options.
b. Select none from the Convergence Criterion drop-down list.
c. Click OK.
3. Create a surface report definition for the voltage at the positive tab.
Solution → Reports → Definitions → New → Surface Report → Area-Weighted Average...
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Setup and Solution
a. In the Surface Report Definition dialog box, enter surf-mon-1 for Name.
b. Select Battery Variables... and Passive Zone Potential from the Field Variable drop-down
lists.
c. From the Surfaces selection list, select tab_p.
d. In the Create group box, enable Report Plot and Print to Console.
e. Click OK to save the surface report definition and close the Surface Report Definition dialog
box.
f.
Modify the attributes of the plot axes.
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Simulating a 1P3S Battery Pack Using the Battery Model
Solution → Monitors → Report Plots → surf-mon-1-rplot
i.
Edit...
In the Edit Report Plot dialog box, under the Plot Window group box, click the Axes...
button to open the Axes dialog box.
ii. Select the X axis and set Precision to 0.
iii. Click Apply.
iv. Select the Y axis and set Precision to 2.
v. Click Apply and close the Axes dialog box.
Note:
You must click Apply to save the modified settings for each axis.
vi. Ensure that time-step is selected from the Get Data Every drop-down list.
vii. Click OK to close the Edit Report Plot dialog box.
4. Create a volume report definition to monitor the maximum temperature in the domain.
Solution → Reports → Definitions → New → Volume Report → Max...
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Setup and Solution
a. In the Volume Report Definition dialog box, enter vol-mon-1 for Name.
b. Select Temperature... and Static Temperature from the Field Variable drop-down lists.
c. From the Cell Zones selection list, select all zones.
d. In the Create group box, enable Report Plot and Print to Console.
e. Click OK to save the volume report definition settings and close the Volume Report
Definition dialog box.
f.
Modify the attributes of the plot axes.
Solution → Monitors → Report Plots → vol-mon-1-rplot
i.
Edit...
In the Edit Report Plot dialog box, under the Plot Window group box, click the Axes...
button to open the Axes dialog box.
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Simulating a 1P3S Battery Pack Using the Battery Model
ii. Select the X axis and set Precision to 0.
iii. Click Apply.
iv. Select the Y axis and set Precision to 2.
v. Click Apply and close the Axes dialog box.
vi. Ensure that time-step is selected from the Get Data Every drop-down list.
vii. Click OK to close the Edit Report Plot dialog box.
5. Save the case file (1P3S_battery_pack.cas.h5).
File → Write → Case...
27.4.3.6. Obtaining Solution
1. Initialize the field variables using the Standard Initialization method.
Solution →
Initialization
a. Retain the selection of Standard from the Initialization Methods group box.
b. Click Initialize.
Note:
Warning messages are printed in the Fluent console informing you about interior
zones between different solids. Such messages appear when two adjacent solid
zones separated by an interior face type are using two different materials. The
message suggests using the mesh/modify-zones/slit-interior-between-diff-solids
text command to slit the interior zone between solid zones of differing materials
to create a wall/wall-shadow interfaces. In general, the material property interpolation at wall/wall-shadow is more accurate if different materials are used at two
sides of an interface. However, the battery model is implemented in such a way
that both treatments are equivalent, and such messages could be ignored..
You do not need to modify the Initial Values in the Solution Initialization task page, because these values are not used for initialization. The ANSYS Fluent solver automatically
computes the initial condition for UDS0 and UDS1.
2. Run the simulation.
Solution → Run Calculation
a. Set Time Step Size to 30 seconds and No. of Time Steps to 50.
b. Click Calculate and run the simulation up to 1500 seconds.
The residual plot, the history of the voltage at the positive tab and the history of the maximum temperature in the domain are shown in Figure 27.5: Residual History of the Simula-
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Setup and Solution
tion (p. 1021), Figure 27.6: Surface Report Plot of Discharge Curve at 200W (p. 1021), and Figure 27.7: Volume Report Plot of Maximum Temperature in the Domain (p. 1022), respectively.
Figure 27.5: Residual History of the Simulation
Figure 27.6: Surface Report Plot of Discharge Curve at 200W
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Simulating a 1P3S Battery Pack Using the Battery Model
Figure 27.7: Volume Report Plot of Maximum Temperature in the Domain
c. Save the case and data files (1P3S_battery_pack.cas.h5 and 1P3S_battery_pack.dat.h5).
File → Write → Case & Data...
27.4.4. Postprocessing
In this section, postprocessing options for the MSMD battery model solution are presented.
1. Display the vector plot of current density.
Results → Graphics → Vectors → New...
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Setup and Solution
a. Enter vector-current-dens for Vector Name
b. In the Vectors dialog box, select current-density-j from the Vectors of drop-down list.
c. Select Battery Variables... and Current Magnitude from the Color by drop-down list.
d. Click the Toggle Tree View button next to the Surfaces filter and from the drop-down list,
select Surface Type (under Group By).
e. From the Surfaces selection list, select Wall.
The surfaces of the "wall" type are automatically selected in the Surfaces list.
f.
In the Options group, enable Draw Mesh and set the mesh display options as desired.
g. Select arrow from the Style drop-down list.
h. Set Scale to 0.003.
i.
Click Vector Options....
i.
In the Vector Options dialog box, enable Fixed Length.
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Simulating a 1P3S Battery Pack Using the Battery Model
All vectors in your plot will be displayed with the same lengths.
ii. Set Scale Head to 0.1.
iii. Click Apply and close the Vector Options dialog box.
j.
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Click Save/Display and close the Vectors dialog box.
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Setup and Solution
Figure 27.8: Vector Plot of Current Density
Note:
Use the Headlight and Lighting display options under the View ribbon tab to
manipulate the graphics display.
2. Display the contour plot of the temperature.
Results → Graphics → Contours → New...
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Simulating a 1P3S Battery Pack Using the Battery Model
a. Enter contour-temp for Contour Name.
b. Select Banded in the Coloring group box.
c. From the Contours of drop-down list, select Temperature... and Static Temperature.
d. Click the Toggle Tree View button next to the Surfaces filter and from the drop-down list,
select Surface Type (under Group By).
e. From the Surfaces selection list, select Wall.
f.
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Click Save/Display and close the Contours dialog box.
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Setup and Solution
Figure 27.9: Contour Plot of Temperature
3. In a similar manner, display the contour of Ohmic heat source.
Results → Graphics → Contours → New...
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a. Enter contour-ohmic-source for Contour Name.
b. Select Banded in the Coloring group box.
c. From the Contours of drop-down list, select Battery Variables... and Joule Heat Source.
d. From the Surfaces selection list, select Wall.
e. Click Save/Display and close the Contours dialog box.
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Setup and Solution
Figure 27.10: Ohmic Heat Generation Rate
4. In a similar manner, display the contour of the total heat source.
Results → Graphics → Contours → New...
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a. Enter contour-total-source for Contour Name.
b. Select Banded in the Coloring group box.
c. From the Contours of drop-down list, select Battery Variables... and Total Heat Source.
d. From the Surfaces selection list, select Wall.
e. Click Save/Display and close the Contours dialog box.
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Summary
Figure 27.11: Total Heat Generation Rate
5. Save the case file (1P3S_battery_pack.cas.h5).
File → Write → Case...
27.5. Summary
This tutorial has demonstrated the use of the MSMD battery model to perform electrochemical and
heat transfer simulations for battery packs. You have learned how to set up and solve the problem for
the battery pack of the 1P3S configuration using the NTGK Battery submodel. You have also learned
some of the postprocessing capabilities available in the MSMD battery model.
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Chapter 28: In-Flight Icing Tutorial Using Fluent Icing
28.1. Fluent Airflow on the Clean NACA0012 Airfoil
The objective of this tutorial is to obtain an airflow solution around a clean NACA0012 airfoil, using
Fluent and Fluent Icing, that is suitable for icing calculations.
Note:
In this tutorial, the Fluent Airflow Solver is used. If you would like to use the FENSAP Airflow
solver instead, go to the FENSAP Airflow on the Clean NACA0012 Airfoil (p. 1089).
Fluent Icing requires a license with Enterprise licensing level. This license is consumed by
the solver.
Download the fluent_icing.zip file here.
This file contains a NACA0012 grid that consists of 114,700 nodes and 56,810 hexahedral cells. Symmetry
conditions are imposed on each spanwise boundary of the grid. The airfoil chord length is 0.5334 meters
(21 inches) and the depth of elements along the span (Z-direction) is 0.1 meters. A no-slip wall boundary
is imposed on the airfoil surface.
Since the flow is viscous and turbulent, grid points have been clustered around the airfoil to better
capture the boundary layer and wake. The initial cell height is 2.5e-6 chords, set up such that the
maximum Y+ is below 1 in the first layer, and the expansion ratio is 1.14 in the normal direction. These
are fine-grid settings that are required to capture the boundary layer. Far-field conditions are imposed
on the outer surface of the grid. The mesh density can be considered medium.
Note:
FENSAP-ICE modules in Fluent Icing solve only 3D problems. In order to solve pure 2-D
problems, it is recommended to generate 3D grids by extruding these 2D domains along
their span or thickness. One single element is sufficient to represent span or thickness of the
3D domain. In this manner, Fluent and Fluent Icing are always executed in 3-D mode.
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Figure 28.1: NACA0012 Structured C-Mesh Overview and Close-Up
This chapter is broken down into two parts:
• Setting up a Fluent Airflow Simulation on a Clean NACA0012 Airfoil (p. 1034): In this section, the
Fluent Solution Workspace is used to setup a clean airflow simulation that is suitable for icing
simulations within Fluent Icing. Moreover, there are a number of settings that are available in
the Fluent Solution Workspace that are not available in Fluent Icing, for instance extra boundary
conditions, solution methods and controls as well as reports and monitoring capabilities. Therefore,
it is normal for a user to begin their simulation inside the Fluent Solution Workspace before
moving onto Fluent Icing. Once the desired setup has been performed, a .cas.h5 file is written
which can then be imported to Fluent Icing.
• Conducting a Fluent Airflow Simulation on Clean NACA0012 Airfoil (p. 1037): In this section, the
.cas.h5 file from the previous section will be loaded into Fluent Icing in order to compute its
airflow solution. Performing this calculation in Fluent Icing will ease the set-up of subsequent
simulations (Rough Airflow, Droplet and Icing simulations) as described in Fluent Airflow on the
Rough NACA0012 Airfoil (p. 1042) through Fluent Icing Ice Accretion on the NACA0012 (p. 1065).
The naca0012.cas.h5 file has already been setup properly for direct use in Conducting a Fluent
Airflow Simulation on Clean NACA0012 Airfoil (p. 1037). Therefore, it is not required to work-through
Setting up a Fluent Airflow Simulation on a Clean NACA0012 Airfoil (p. 1034). However, if this is your first
time running an icing simulation with Fluent, it is recommended to continue with the steps shown in
Setting up a Fluent Airflow Simulation on a Clean NACA0012 Airfoil (p. 1034) to learn how to properly
setup a Fluent case.
28.1.1. Setting up a Fluent Airflow Simulation on a Clean NACA0012 Airfoil
1. Launch Fluent on your computer. In the Fluent Launcher window, select Solution. Set the Dimension as 3D, pick Double Precision under Options, and set the number of Solver Processes
between 2 and 4 CPUs. Click Start to launch the Fluent Solution Workspace.
2. Read the case file by going to File → Read → Case.... Browse to and select the extracted file
../workshop_input_files/Input_ Grid/Naca0012/naca0012.cas.h5.
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Fluent Airflow on the Clean NACA0012 Airfoil
The table below lists the flight conditions used in the following airflow simulation.
Table 28.1: Simulation Flight Conditions
Characteristic Length
0.5334 m
Speed
102.8 m/s
AoA
4 deg
Pressure
101325 Pa
Temperature
265.67 K (-7.48 °C)
3. From the top bar navigation menu, select Physics → Solver → Operating Conditions.... Set the
Operating Pressure (pascal) to 101325 Pa. Press OK.
4. From the side menu, select General under Setup. Ensure that the Solver is set to Type: PressureBased, Velocity-Formulation: Absolute, and Time: Steady.
5. From the side menu, in Models,
• Select Energy and ensure that it is turned on.
• Double-click Viscous to open the Viscous Model menu. There are different turbulence
models that can be selected. For icing applications, it is strongly recommended to use the
popular k-ω SST model. Therefore, change the Model to k-omega (2 eqn) and SST. In the
Options section, enable Viscous-Heating and Production Limiter. In the Model Constants
section, change the Energy Prandtl Number and Wall Prandtl Number to 0.9, to be
consistent with FENSAP-ICE, and the Production Limiter Clip Factor to 10. Press OK.
6. From the side menu, click Materials → Fluid and double-click air to open the air properties. Set
the Density to ideal-gas. Click Change/Create to save the air properties, then press Close.
Note:
Fluent Icing automatically sets the specific heat, thermal conductivity and viscosity
of air that are appropriate for icing simulations. Therefore, if this case file is later
used by Fluent Icing, these parameters can be left as is in Fluent Solution. In the
event, that this is not the case and that the case file is used inside FENSAP-ICE,
please follow these steps.
• Set the Cp (Specific Heat) to 1004.6882 j/kg.K. This value is equal to 7/2 R air when air
is treated as an ideal gas. In FENSAP-ICE, the gas constant R is always 287.05376 j/kg.K.
• Set the Thermal Conductivity to 0.023439363 W/m.K and Viscosity to 1.6801754e05 Kg/m.s. These values have been computed using the equations presented under Airflow
within the Fluent User's Guide.
Note:
For simplicity, thermal conductivity and viscosity equations presented in the Fluent
Icing User’s manual are shown below:
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In these equations,
refers to the ambient air static temperature.
,
and
are equal to 0.00216176 W/m/K3/2, 288 K and 17.9*10-6 Pa.s, respectively.
7. From the side menu, click Boundary Conditions,
• Click Inlet and double-click pressure-far-field-4 to set the far field boundary conditions.
a. In the Momentum panel, set the Gauge Pressure (pascal) to 0 Pa and the Mach
Number to 0.31461268. Set the Coordinate System to Cartesian (X, Y, Z) and the
X, Y and Z-Component’s to 0.99756405, 0.069756474, and 0. This simulates a 4degree angle of attack (AoA) airflow. In the Turbulence section, set the Specification
Method to Intensity and Viscosity Ratio. Then, set the Turbulence Intensity (%) to
0.08% and the Turbulent Viscosity Ratio to 1e-05.
b. In the Thermal panel, set the Temperature (k) to 265.67 K. Press OK.
• Click Wall and double-click wall-5. In the Momentum panel, set the Shear Condition to
No Slip. In the Thermal panel, set the Thermal Conditions to Temperature. Set the
Temperature (k) to 280.929174208 K, and press OK. This temperature corresponds to
the Adiabatic stagnation temperature + 10K, as required for standard external icing simulations with FENSAP-ICE. Repeat this process for wall-6, wall-7 and wall-8.
8. From the side menu, click Symmetry and ensure that symmetry-9 and symmetry-10 boundaries
are set to symmetry type by right-clicking symmetry and selecting Type → symmetry.
9. Double-click Reference Values from the side menu. Under Compute from, select pressure-farfield-4. Set the Area to 0.05334 m2 and the Length to 0.5334 m. These reference values will
be used only for postprocessing purposes. For instance, force coefficients use the reference area,
density, and velocity.
10. Double-click Solution and then Methods on the side menu. Set the Pressure-Velocity Coupling
scheme to Coupled. Under Spatial Discretization, set the Gradient to Green-Gauss Node Based
and the remaining options to Second or Second Order Upwind.
Note:
If the Fluent simulation diverges after a few iterations, enabling High Order Term Relaxation will improve its convergence. In the current tutorial, there is no need to enable
this term.
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Fluent Airflow on the Clean NACA0012 Airfoil
11. Double-click Controls under Solution. Set the Flow Courant Number to 50. In Under-Relaxation
Factors, set Turbulent Viscosity and Energy to 0.9.
Note:
Pseudo transient could have also been used in this tutorial.
12. From the side menu, double-click Monitors and then Residuals. Modify the Absolute Criteria
for convergence to 1e-12 for all parameters. Make sure that the Print to Console and the Plot
are enabled and ensure that Monitor and Check Convergence are selected for all parameters.
Since this 3D simulation should provide a 2D solution, uncheck z-velocity under Monitor but
keep Check Convergence checked.
13. Monitor the drag and lift coefficients during the simulation. Follow the bullet points describe below
if these settings are not part of the current case file. Otherwise, you will monitor these coefficients
twice.
• In the side menu, double-click Report Definitions under Solution, select New → Force Report
→ Drag.... Change the Name to report-drag and set the Force Vector to 0.99756405,
0.069756474, and 0. Enable Report Plot, and Print to Console under Create, and Drag
Coefficient under Report Output Type. Select wall-5, wall-6, wall-7 and wall-8 under the
Wall Zones section. Press OK.
• In the Report Definitions window, select New → Force Report → Lift. Change the Name to
report-lift and set the Force Vector to -0.069756474, 0.99756405, and 0. Enable
Report Plot, and Print to Console under Create and Lift Coefficient under Report Output
Type. Select wall-5, wall-6, wall-7, and wall-8 under the Wall Zones section. Press OK and
close the Report Definitions window.
14. Go to File → Write → Case... to save the setup case file for use in the next section. Name this file
naca0012.cas.h5.
15. Go to File → Exit to close the Fluent Solution Workspace.
28.1.2. Conducting a Fluent Airflow Simulation on Clean NACA0012 Airfoil
1. Launch Fluent on your computer. In the Fluent Launcher window, select Icing. Icing is only
available if Capability Level → Enterprise is selected. The usage of the Icing feature requires a
Fluent license with the Enterprise license level. Set the number of Solver Processes between 2
and 4 CPUs. Click Start to launch Fluent Icing.
2. Once Fluent Icing opens, the Project tab will be displayed by default. In the Project's top ribbon
panel, select Project → New... and enter FLUENT_ICING_NACA0012 to create a new Project
folder.
3. In the Project’s top ribbon, select Simulations → Import case, and browse to and select the
../workshop_input_files/Input_Grid/Naca0012/naca0012.cas.h5 file from the
extracted fluent_icing.zip archive or the naca0012.cas.h5 saved in Setting up a Fluent
Airflow Simulation on a Clean NACA0012 Airfoil (p. 1034). A New simulation window will appear.
Enter the Name of the new simulation as naca0012_icing, and check to enable Load in
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In-Flight Icing Tutorial Using Fluent Icing
solver. A new Simulation folder will be created in your Project folder, and the naca0012.cas.h5
file will be imported.
4. After the .cas.h5 file has been successfully loaded, the Simulation tab is displayed a new simulation tree appears under naca0012_icing (loaded) in the Outline View window, and the
naca0012 grid is displayed inside the Graphics window, located on the right of your screen.
5. In the Outline View window, select Setup under naca0012_icing (loaded) and, in its properties
window, uncheck Particles and Ice.
6. Inside the Outline View window, right-click the Airflow icon located under Setup and select
Update with Fluent Case settings to make sure that the previously setup Fluent simulation settings
are properly transferred to Fluent Icing.
7. Inside the Outline View window, right-click the Fluent icon located under Airflow and select Set
to default Air properties. This automatically sets the air properties, suggested for icing simulations,
from the current reference air temperature. The values of air properties have been computed using
the equations presented in Airflow within the Fluent User's Guide.
Note:
For simplicity, thermal conductivity and viscosity equations presented in the Fluent
Icing User’s manual are shown below:
In these equations,
refers to the ambient air static temperature.
,
and
are equal to 0.00216176 W/m/K3/2, 288 K and 17.9*10-6 Pa.s, respectively.
8. Under Solution, right-click Airflow from the side menu. Select Initialize. A Hybrid initialization
is executed using the settings of the original case file.
9. Under Solution, click Airflow to display the properties of Properties - Airflow panel. Increase
the Number of iterations to 1000. A steady state simulation will be executed since the original
case file contains steady state settings.
Note:
Transient calculations are not yet supported. Therefore, the original case file must be
set-up for a steady state simulation.
10. Right-click the Airflow icon under Solution and select Calculate to launch this simulation. A New
run window will appear. Set the Name of the new run to flow_clean.
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Fluent Airflow on the Clean NACA0012 Airfoil
11. Once the computation is complete, the solution file, out.dat.h5, will be written inside the new
run directory, naca0012_icing/flow_clean.
12. Take a look at the convergence history of this simulation in the Plots window located at the right
of your screen. By default, the Plots window shows all Residuals of the governing equations at
each iteration. It is possible to show the residual of a given governing equation by selecting the
governing equation next to Curve located at the top of the Plots window. If other reports Reports
have been defined in the original case file, they will appear as an option next to Curve. In this
tutorial, the input case file contained lift and drag coefficient reports. Examine the convergence
of these coefficients listed as report-lift and report-drag. Lift and drag coefficients have converged
to 4.5105e-01 and 9.5196e-03 respectively.
The following three figures show the convergence of residuals and lift and drag coefficients.
Figure 28.2: Scaled Residuals
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Figure 28.3: Convergence of Lift and Drag Coefficients of the Clean Airfoil
Figure 28.4: The Residual Values
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Fluent Airflow on the Clean NACA0012 Airfoil
13. Go to the ribbon bar of your Fluent Icing window and, under View → Quick-view → Contour,
choose Heat flux (walls) to output the convective heat flux over the clean NACA0012. See Figure 28.5: Convective Heat Flux over the Clean NACA0012 Airfoil (p. 1041).
Figure 28.5: Convective Heat Flux over the Clean NACA0012 Airfoil
14. In the ribbon bar of your Fluent Icing window, select the Project tab. The left-side panel will
switch to the Project View. The naca0012_icing (loaded) simulation now contains the run folder
flow_clean, which contains the solution file out.dat.h5. Moreover, (current) is listed next to
the run folder to show that this is the current run, and the out.dat.h5 file is displayed in bold
to show that this file is currently loaded.
Note:
The Fluent Icing settings that you used to perform the flow_clean run are saved in a
run.settings file that is located inside the flow_clean run folder. If you would like
to load these settings at any point in the future, you may right-click the flow_clean
folder and select Load settings. The run.settings file itself is hidden by default.
To display this file, you may right-click Name under Project View and select Show
hidden items. Repeat these steps to disable Show hidden files before continuing with
this tutorial.
15. Select the Simulation tab to go back to the Simulation Outline View.
Caution:
If you would like to continue with the next tutorial, do not close Fluent Icing.
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28.2. Fluent Airflow on the Rough NACA0012 Airfoil
The objective of this tutorial is to obtain an airflow solution around a rough NACA0012 airfoil, using
the Fluent airflow solver within Fluent Icing, and to use this solution for water catch and ice accretion
simulations. Completion of the previous tutorial, Fluent Airflow on the Clean NACA0012 Airfoil (p. 1033),
is required before beginning this tutorial. Ice forms surface roughness as it accretes. This roughness
increases the momentum deficit and the skin friction, which in turn thickens the boundary layer and
increases drag. Convective heat flux is also in- creased through additional turbulent conductivity within
the boundary layer. It is therefore essential to properly model the roughness produced naturally by the
ice accretion process to obtain realistic ice shapes. Fluent Icing models roughness by applying an appropriate sand-grain roughness height distribution over iced walls. In Fluent Icing, this height can be
specified on each wall as a constant value, or as a distribution via empirical or analytical methods such
as ice bead modeling. See Surface Roughness within the FENSAP-ICE User Manual or the Setup →
Boundary Conditions → Wall and Setup → Ice sections within the Fluent User's Guide for more details
on surface roughness.
Note:
If you closed your Fluent Icing session since the completion of the last tutorial, you must
reopen your project and load your previous simulation and settings. To do this, open Fluent
Icing, select Project → Open..., and navigate to and select your FLUENT_ICING_NACA0012.flprj project file. Once the project is opened, right-click the
naca0012_icing simulation folder, and select Load in solver. The simulation will be opened,
and your window display will switch to the Outline View, with a simulation tree appearing
under naca0012_icing (loaded). To ensure that you are working from the most recent settings, go back to the Project View, right-click the flow_clean run, and select Load settings.
Finally, go back to the Simulation tab to continue with the tutorial.
1. Inside the Outline View, select Setup under naca0012_icing (loaded) and, in its Properties window,
make sure that Particles and Ice are unchecked.
2. Under Setup → Boundary Conditions, update the following wall surfaces:
• Select the wall-5 boundary. In its property panel, set Wall Roughness to High roughness
for Icing and set its Roughness Height (m) to 0.0005 m.
• Right-click wall-5 boundary. Select Set temperature to Adiabatic + 10. The Temperature
[K] is now set to 280.929 in wall-5’s property panel. The value of the surface temperature
should be several degrees above the adiabatic stagnation temperature in order to compute
heat fluxes with the correct sign on the entire aircraft surface.
• Repeat this process for wall boundaries wall-6, wall-7, and wall-8.
3. Under Solution, right-click Airflow from the side menu. Select Initialize. A Hybrid initialization is
executed.
4. Under Solution → Airflow, set the Number of iterations to 1000.
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Fluent Airflow on the Rough NACA0012 Airfoil
5. Right-click the Airflow icon under Solution and select Calculate to launch this simulation. A window
will appear asking if the current run should be continued. Select No. A new run window will appear.
Set the Name of the new run to flow_rough. Press OK.
Note:
If you closed your Fluent Icing session after the completion of the last tutorial, a window
will appear asking to create a new run once you click Calculate. Set the Name of the
new run to flow_rough and press OK.
6. Once the computation is complete, the solution file will be written inside the Project Run directory
as naca0012_icing/flow_rough/out.dat.h5.
7. Take a look at the convergence history of this simulation in the Plots window located at the right
of your screen.
In the Plots window, the residuals and reports, previously defined in the original case file, are
provided at each iteration. Examine the convergence of Residuals, and lift and drag coefficients
that are listed as report-lift and report-drag, by properly selecting them next to Curve in the Plots
window. Lift and drag coefficients have converged to 4.0575e-01 and 1.9851e-02 respectively. This
is approximately a 10% loss in lift and a 108% increase in drag from the clean NACA0012 airfoil. The
increase in drag due to roughness is quite high in this case, partly because the roughness height is
significant for the size of the airfoil (0.5334 m chord) and the whole surface is set as rough. In general, only the first 10% of the chord (leading edge) gets iced. For icing calculations, the flow solution
should be computed with roughness set everywhere since there is no knowledge of the droplet
impingement zone or the icing limits a priori. The following three figures show the convergence of
residuals and lift and drag coefficients.
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Figure 28.6: Scaled Residuals
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Fluent Airflow on the Rough NACA0012 Airfoil
Figure 28.7: Convergence of Lift and Drag Coefficients of the Rough Airfoil
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Figure 28.8: The Residual Values
8. Go to the ribbon bar of your Fluent Icing window and, under View → Quick-view → Contour,
choose Heat flux (walls) to output the convective heat flux over the rough NACA0012 on the
Graphics window located at the right of your screen. See Figure 28.9: Convective Heat Flux Over
the Rough NACA0012 Airfoil (p. 1046).
Figure 28.9: Convective Heat Flux Over the Rough NACA0012 Airfoil
Caution:
If you would like to continue with the next tutorial, do not close Fluent Icing.
28.3. Droplet Impingement on the NACA0012
The objectives of this tutorial are to compute the droplet concentration around the NACA0012 airfoil
and to compare the collection efficiency of a monodispersed droplet simulation to a statistically-distributed droplet diameter solution. Completion of Fluent Airflow on the Rough NACA0012 Airfoil (p. 1042) is
required before continuing.
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In a monodispersed droplet calculation, a single droplet diameter represents the icing cloud that the
aircraft is flying in. In reality, icing clouds never contain only one size of droplets; but a distribution of
droplet sizes. When running a single droplet diameter, the median volumetric diameter (MVD) of the
droplets in the cloud is chosen as the monodispersed value. If a more accurate droplet solution is
needed, then a distribution of droplet sizes can be solved for, where the MVD of this distribution matches
that of the cloud.
You are invited to read Particles and Inlet Types within the Fluent User's Guide for more information
on how to set up the input parameters of droplets and/or crystals.
Note:
If you closed your Fluent Icing session since the completion of the last tutorial, you must
reopen your project and load your previous simulation and settings. To do this, open Fluent
Icing, select Project → Open..., and navigate to and select your FLUENT_ICING_NACA0012.flprj project file. Once the project is opened, right-click the
naca0012_icing simulation folder, and select Load in solver. The simulation will be opened,
and your window display will switch to the Outline View, with a simulation tree appearing
under naca0012_icing (loaded). To ensure that you are working from the most recent settings, go back to the Project View, right-click the flow_rough run, and select Load settings.
Particle simulation requires an airflow solution, therefore, to ensure that the solution of
flow_rough is properly loaded into Fluent Icing, in Project View, right-click the out.dat.h5
file under flow_rough and select Load. Finally, go back to the Simulation tab to continue
with the tutorial.
28.3.1. Monodispersed Calculation
In this section, you will learn how to set-up and launch a monodispersed droplet simulation using
Fluent Icing.
1. Select Simulation in the top ribbon and go to the Outline View. Select Setup under
naca0012_icing (loaded). In its Properties window, make sure that Airflow and Particles are
checked and uncheck Ice.
Note:
Setup, Solution and Results settings of the airflow around the NACA0012 have already
been setup in Fluent Airflow on the Rough NACA0012 Airfoil (p. 1042). Therefore, they
do not need to be updated.
2. Under Setup → Particles, activate Droplets in Type. Leave the other options unchecked.
3. Go to Droplets, inside Setup → Particles. In the properties window of Droplets,
• under Droplet conditions, set the LWC [kg/m3] to 0.00055 and the Droplet diameter [microns] to 20.
• under Particles distribution, keep Monodispersed since we will conduct a water catch simulation using a single droplet size.
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• under Model, keep Water as the Droplet drag model. This is the default drag law for droplet
particles.
4. Under Setup → Boundary Conditions, go to pressure-far-field and make sure that, in its properties window, under Particles, From ref. conditions is selected and Droplet velocity vector
remains unchecked. The From ref. conditions option will apply the Droplet conditions, located
inside the Propeties - Droplets window, at the inlet of the pressure-far-field, in this case, the
LWC and the MVD. If Droplet velocity vector remains unchecked, the airflow velocity is imposed
as the droplet velocity at the inlet. The relative velocity between air and droplets is considered
to be zero at far-field.
Note:
When configuring particle flow simulations, boundary conditions are only specified at
inlets.
5. Under Solution → Particles, set 300 as the Number of Iterations in Run settings. Keep the default
settings in Solver and Initialization.
Note:
Inside Initialization, From airflow conditions uses the airflow direction specified in
Setup → Airflow as the initial velocity of droplets.
6. Right-click Particles under Solution and choose Calculate to launch the droplet particle simulation
in standalone mode. A new window will appear requesting a name for the new run. Name the
new run droplets_mvd.
The calculation stops when the convergence level reaches the convergence limits set on the Residual cut-off and on the Change in total beta. Otherwise, the simulation continues until it
reaches 300 iterations. In the Plots window, you can look at Residuals, Droplets – Residual –
Average, Droplets – Residual – LWC, Droplets – Residual – Momentum, etc. curves and the
Droplets -Total Beta and Droplets - Change in Total Beta convergence curves.
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Figure 28.10: Convergence of Residuals: Momentum, LWC and Average Residuals
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Figure 28.11: Convergence of Total Beta and Change in Total Beta Curves
Often the solution in the wake of the droplet flow is still converging while the impingement at
the surfaces is fully converged. If you wish to converge the wake and the shadow zones further,
the Residual cut-off of the Properties - Particles panel under Solution should be reduced and
the Number of iterations should be increased. The droplet wake is usually not of interest and it
is sufficient to achieve convergence of the total beta alone.
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Droplet Impingement on the NACA0012
7. When calculations are completed, you may use Quick-View to view the results. Go to the ribbon
bar of your Fluent Icing window and, under View → Quick-view → Contour, choose Collection
Efficiency to output the water catch of the monodispersed droplets over the NACA0012. See
Figure 28.12: Collection Efficiency of Monodispersed Droplets over a NACA0012 (p. 1051).
Figure 28.12: Collection Efficiency of Monodispersed Droplets over a NACA0012
8. Repeat these steps to output the LWC around the NACA0012. Blue contours define the shadow
zone where there is an absence of water droplets. See Figure 28.13: LWC of Monodispersed Droplets
Around a NACA0012 (p. 1052).
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Figure 28.13: LWC of Monodispersed Droplets Around a NACA0012
9. Select Project from the ribbon menu. Notice that naca0012_icing (loaded) simulation now contains
the droplets_mvd run which contains the final droplet solution, out.droplet. In addition to QuickView, you can also open the results in Viewmerical from the Project View. Right-click the
out.droplet solution file and select View with Viewmerical. A Viewmerical window will appear
allowing you to further post-process the droplet results.
10. Before you move on to the next tutorial, go back to the Simulation view or Outline View panel.
Caution:
Do not close Fluent Icing.
28.3.2. Langmuir-D Distribution
There are several cloud droplet size distributions that have been published in the literature. The distributions published by Langmuir have been used by NACA to determine the MVDs currently listed
in Appendix C, which is used for icing certification of aircraft. Advisory Circular No 20-37A from FAA
suggests using Langmuir-D distribution for MVDs up to 50 microns. For more details on these distributions, you can consult the Advisory Circular, and also the book by Irving Langmuir, The Collected
Works of Irving Langmuir (New York, Pergamon Press, 1960).
The most important reason for considering an analysis using a distribution is that there are droplets
larger than the MVD in the distribution, which can impinge further back on the top and bottom of
the airfoil, creating a thin but rough layer of ice that can have adverse effects on aerodynamics and
control. In this case, solutions for each droplet size of a given distribution are calculated separately.
The final solution is then created as a composite of all solutions using weights on each droplet size.
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Droplet Impingement on the NACA0012
In this tutorial, you will use the set-up created in Monodispersed Calculation (p. 1047) as a starting
point.
1. Without closing the previous Fluent Icing session (Monodispersed Calculation (p. 1047)), in the
Outline View panel, go to Setup → Particles → Droplets. In the Properies - Droplets window,
under Particles distribution, set Droplet distribution to Langmuir D.
Note:
The current version of Fluent Icing only supports pre-defined droplet size distributions
(Langmuir B to E). User defined distributions are not yet supported. Below is a representation of a Langmuir D distribution and the droplet diameters that are used to represent this distribution. Note that this figure is taken from FENSAP-ICE native user interface and is currently unavailable in the Fluent Icing user interface.
In the figure above, the droplet diameters are on the horizontal axis, and the weights (the percentage of droplets of a given diameter contained in the cloud) are on the vertical axis. The individual
weights are shown with the blue curve, and the overall sum, cumulative weight, is shown with
the red curve. On the red curve, the data points are plotted at the mid-range of their cumulative
weight intervals. For example, the 20 microns droplet, which happens to be the MVD, covers the
cumulative weight range of 35% to 65% and it is therefore plotted at 50% cumulative weight on
the red curve.
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A Particle droplet simulation is run for each droplet size shown in the above table.
2. Go to Solution → Particles, in its properties window, check Save distribution solutions under
Output.
This will allow you to save a droplet solution for each droplet size simulated. Otherwise, only the
combined solution of the distribution is saved. Keep all the other settings the same.
3. Right-click Particles under Solution, choose Calculate to run the calculation. A window will appear
asking if you would like to continue the current run. Choose No. A new run window will appear.
Set the Name of the new run to droplets_langd. Individual runs will be executed one after
the other, and the results will be combined.
4. When calculations are completed, you may use Quick View to view the results. Go to the ribbon
bar of your Fluent Icing window and, under View → Quick-view → Contour, choose Collection
Efficiency to output the water catch of the Langmuir D droplet distribution over the NACA0012.
See Figure 28.14: Collection Efficiency of Droplets with Langmuir-D Distribution over a
NACA0012 (p. 1054).
Figure 28.14: Collection Efficiency of Droplets with Langmuir-D Distribution over a NACA0012
5. Repeat these steps to easily output the LWC around the NACA0012. Blue contours define the
shadow zone, absence of water droplets. See Figure 28.15: LWC of Droplets with Langmuir-D Distribution Around a NACA0012 (p. 1055).
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Droplet Impingement on the NACA0012
Figure 28.15: LWC of Droplets with Langmuir-D Distribution Around a NACA0012
6. Select Project from the ribbon menu. Notice that naca0012_icing (loaded) simulation now contains
the droplets_langd run. This run has a combined droplet solution out.droplet as well as each
individual droplet solution from out.droplet.01 through out.droplet.07. To link each numbered
droplet solution to a droplet size of the Langmuir D distribution, in the Project ribbon, select
Columns under Display. A Project window appears. Click the + sign besides Metadata to expand
the list of parameters associated to each run and solution. Scroll-down and select Droplets::DDiam and click OK. A D-Diam column appears next to Name inside the Project panel. This column
clearly identifies the droplet diameter used to obtain each out.droplet.xx solution.
Note:
In addition to Quick View, you may open the results in Viewmerical from the project
menu. To display the combined droplet solution in Viewmerical, right-click the
out.droplet solution file and select View with Viewmerical. Alternatively, to display
an individual droplet solution file, right-click the out.droplet.xx file of your choice and
select View with Viewmerical. A Viewmerical window will appear allowing you to
further post-process the droplet results.
7. Before you move on to the next tutorial, go back to the Simulation panel.
Caution:
Do not close Fluent Icing if you would like to proceed with the next section.
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28.3.3. Post-Processing Using Viewmerical
To complement the built-in post-processing, ANSYS distributes Viewmerical and CFD-Post with the
installation package. In this tutorial, you will use Viewmerical to post-process your droplet results. In
the next tutorial, you will use CFD-Post to post-process your icing results.
Viewmerical is a light-weight graphical display tool specifically designed for in-flight icing solutions
and applications. Viewmerical can display solution field contours, velocity vectors, planar cuts through
the volumes, 2D graphs of variables, streamlines, etc. This tutorial will demonstrate some basic features
of Viewmerical while comparing the two droplet solutions obtained in the previous sections.
1. In Project View, right-click the naca0012_icing → droplets_langd → out.droplet solution file
and choose View with Viewmerical. A message may appear asking if you would like to append
this solution to a previously opened Viewmerical display. Click No.
2. The program will launch and show an isometric display of the entire grid showing the first solution
field, Droplet LWC, of the combined Langmuir D solution.
3. Rename this dataset by double-clicking on the original name, data-out.droplet. A Rename
dataset window appears, write LangD in the text box.
4. Go to the Data tab and then change the Color range to Spectrum 2 – 16.
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Droplet Impingement on the NACA0012
5. Align the view angle with the Z-symmetry plane by right-clicking on the 3D axes on the lower
left, and by choosing Top (Z). Alternatively, you can left-click the Z axis itself.
6. Zoom in on the airfoil. You can use Ctrl + left-click to draw a zoom box, or scroll the mouse wheel
to zoom in and middle-click to pan.
7. Change the font of your legend to bold. Click
on the top left corner of the window and select
Command window; then type BIGFONTS in the command line of the 3dview console and hit
Enter. The legend fonts now become bold.
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8. Using the Camera icon on the upper left corner, you can take a snapshot of the solution window
to capture the following image.
Figure 28.16: LWC of a Langmuir D Droplet Cloud over a NACA0012 at an AoA of 4 Degrees,
Showing the Shadow Zone (Blue Region)
Examine the LWC distribution in the area close to the airfoil. The blue region is called the shadow
zone, where no droplets exist. In between the shadow zone and the free stream, there are bands
of high LWC concentrations which are the enrichment zones forming due to the constriction of
stream tubes in the continuum domain. These features can be of special interest for downstream
aircraft components.
9. Go to the Data tab and choose Collection efficiency-Droplet. Collection efficiency is only displayed
on the walls of your geometry. Go to the Objects tab and uncheck BC_1004 and BC_4300 to
display the collection efficiency distribution only on the walls (BC_2005, BC_2006, BC_2007, and
BC_2008).
Use the left mouse button to rotate, the middle mouse button to pan, and the right-mouse button
to zoom in the airfoil surface to obtain the following figure.
Figure 28.17: Collection Efficiency of a Langmuir D Droplet Cloud on the Surface of the Airfoil
at an AoA of 4 Degrees
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10. For a more in-depth quantitative view, it would be possible to create 2D data plots using Viewmerical. Click the Query tab and enable 2D Plot.
Change the Cutting plane to Z and the horizontal axis to Y.
On the lower right corner of Viewmerical, you can directly modify data sets and solution fields.
Leave them as they are now.
11. The color and thickness of the data curve displayed in the graph can be changed by left clicking
on the cube menu located on the top right and by choosing Curve Settings. Set the curve color
to red and the curve widths to 2 and press OK.
Finally, the following 2D plot is generated.
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Figure 28.18: Collection Efficiency of a Langmuir D Droplet Cloud on the Surface of the Airfoil
at an AoA of 4 Degrees
The maximum beta occurs at the stagnation point, just below the leading edge in this case. The
points on the upper and lower surfaces where beta becomes zero are the impingement limits. In
rime icing cases, all the water that impinges is frozen instantly, therefore icing limits are the same
as the impingement limits. In glaze icing, water can runback and freeze past the impingement
limits. Maximum beta is usually no more than 1.0, and reduces as the droplet flow becomes tangent
to the surface.
12. To save data points of this collection efficiency distribution, go to the cube menu on the top right
and choose Save one file. A new window pops up to browse and name the file that should contain
these data points.
13. You can also open and compare several solution files using Viewmerical. Let’s display simultaneously
all 7 droplet size solutions obtained in Langmuir-D Distribution (p. 1052).
14. Go to Project View. Under the run droplets_langd, right-click its out.droplet.01 file and select
View with Viewmerical.
15. A message appears asking if you would like to append this solution to a previously opened
Viewmerical display. Click Yes.
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16. Inside Viewmerical, rename this new object by double-clicking on its original name in the Object
window and enter LangD-01-44.4um in the window Rename dataset, where 01 indicates the
droplet solution number and 44.4um is the droplet diameter of the droplet solution.
Note:
The droplet diameter of each droplet solution is shown in D-Diam column of the
Project panel of the naca0012_icing (loading) simulation. See step 6 of LangmuirD Distribution (p. 1052).
17. Repeat steps 14 to 16 to load the remaining droplet solutions from out.droplet.02 to
out.droplet.07.
Note:
Alternatively, it is possible to bring each droplet solution by going to the run
droplets_langd folder and by uploading each one of them from Viewmerical. To
do this in Viewmerical, perform the following steps:
• Click the
button located at the right corner of the Object panel. A window
appears to load a pair of files, a grid file and its solution file.
• Click the
folder icon of Grid file and select the naca0012.grid file located
inside your Project and Simulation directory FLUENT_ICING_NACA0012/naca0012_icing/.
• Click the
folder icon of Solution file (optional) and select the
out.droplet.01 file located inside your Project, Simulation and Run directories /FLUENT_ICING_NACA0012/naca0012_icing/droplets_langd.
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• Press the Load button. A new data set is added to the Object panel. Rename
this dataset by double-clicking on its original name and enter LangD-0144.4um in the window Rename dataset, where 01 indicates the droplet solution
number and 44.4um is the droplet diameter of the droplet solution.
• Repeat these steps for the remaining droplet solutions from out.droplet.02 to
out.droplet.07.
18. In Viewmerical, go to the Objects panel, uncheck LangD.
19. Go to the Data panel and click Shared located under Color range. Switch the Data field to Collection efficiency- Droplet.
20. Go to the Query tab, enable 2D plot, and switch the Cutting plane to Z. The graph should display
8 individual beta distributions. click LangD, to disable the LangD curve from the 2D plot. You
can change the color and thickness of the data curve displayed in the graph via the cube menu
on the top right and by choosing Curve Settings. You can also draw a zoom box by Shift + leftclick.
Figure 28.19: Collection Efficiency on the Surface of the Airfoil at an AoA of 4 Degrees,
Langmuir D Droplet Solutions
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Droplet Impingement on the NACA0012
The curve with the lowest beta corresponds to the smallest droplet size (LangD-07-6.2 µm), and
the one with the largest beta corresponds to the largest droplet size (LangD-01-44.4.µm). Smallest
droplets are less ballistic, tend to follow the air flow and avoid the aircraft therefore reducing their
collection efficiency and impingement limits. Larger droplets are more ballistic and they do not
tend to follow the airflow. Therefore, their collection efficiency and impingement are usually
higher than the smallest droplets. In general, this information is crucial to properly design the IPS
power requirements and coverage.
Note:
The difference between beta curves of different droplet sizes become more pronounced
as the aircraft surface size increases. The effect can be dramatic on large blunt surfaces
like fuselage noses or radomes where the contribution from the smaller size droplets
can be negligible if compared to the largest ones. As a result, the composite or combined solution of a Langmuir simulation can be very different from the solution of the
MVD.
21. To compare the LangD result to that of the monodispersed (MVD), go to the Objects panel, check
LangD and uncheck all the other LangD-* objects.
22. Go to Project View. Under the run droplets_mvd, right-click its out.droplet file and select View
with Viewmerical.
23. A message appears asking if you would like to append this solution to a previously opened
Viewmerical display. Click Yes.
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24. Inside Viewmerical, rename this new object by double-clicking on its original name in the Object
window and enter MVD in the window Rename dataset.
25. Go to the Query tab, enable 2D plot, and switch the Cutting plane to Z. The graph should display
9 individual beta distributions. click LangD-01-44.4um to LangD-07-6.2um to disable these curves
from the 2D plot. Change the color of the MVD to red and of the LangD to blue via the cube
menu on the top right and by choosing Curve Settings. Set their width to 2. You can also draw
a zoom box by Shift + left-click.
Figure 28.20: Collection Efficiency on the Surface, Langmuir D vs. Monodisperse
The LangD solution is fairly close to that of the MVD. The impingement limits of the Langmuir D
solution will always be further back due to the inclusion of larger droplets in the distribution. The
maximum beta of the composite is lower than the MVD here. This is not always the case. Based
on the size and shape of the impingement surface, the Langmuir D solution can have a maximum
beta that is several times higher than the MVD. In this case, however, the results of the MVD and
the distribution are close.
26. You will now compare the LWC of the largest and smallest droplet of a Langmuir D distribution.
Go to the Objects panel, uncheck LangD and MVD objects and check LangD-01-44.4um (largest
droplets) and LangD-07-6.2um (smallest droplets).
27. On the lower right corner of Viewmerical, change Collection efficiency-Droplet to Droplet LWC
(kg/m^3).
28. Select LangD-01-44.4um in the Objects panel and choose Horizontal-Left under Split screen
menu.
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Fluent Icing Ice Accretion on the NACA0012
29. Go to the Data tab and change the color range to Spectrum 2 –16.
30. Align the view angle with the Z-symmetry plane and zoom in to capture the following image:
Figure 28.21: LWC Distribution and Shadow Zones for 44.4 Micron Droplets (Left) and 6.2
Micron Droplets (Right)
Observe the difference in the shadow zones. The smallest droplets follow the airfoil very closely
but avoiding it while the largest droplets barely change their path and hit almost straight on,
leaving a larger shadow zone.
28.4. Fluent Icing Ice Accretion on the NACA0012
The objective of this tutorial is to compute ice accretion and water runback on the NACA0012 airfoil at
different icing temperatures. Icing temperature refers to the free stream air temperature at which the
icing is to be computed. Inside Ice, this temperature can be different than what was used for the airflow
free stream temperature. Indeed, the formulation of the heat fluxes in Ice allows to use an air solution
obtained at a temperature different than the intended icing temperature. In this manner, several icing
temperatures can be investigated using the same airflow solution.
Note:
The option to change icing air temperature in icing parameters is provided as a quick
method to obtain different ice shapes with different ambient temperatures. It should be
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understood that this method is not identical in terms of accuracy to running air and droplet
flows independently for each of those temperatures. Change in ambient air temperature
would result in a proportional change in air density which would change the momentum
transfer between air and particles. This would ultimately affect particle flow paths and collection efficiency. For internal flows, where particle thermal equation and/or vapor transport is
enabled, icing air temperature should be kept the same as the reference air temperature.
You are invited to read Setup → Ice and Setup → Boundary Conditions → Wall within the Fluent
User's Guide for more information on how to set up the input parameters of the Ice module.
This tutorial will begin as a continuation of Monodispersed Calculation (p. 1047), so the monodispersed
droplet solution and settings must be loaded.
1. Select Project from the top ribbon menu. To load the settings from the monodispersed run, rightclick the droplets_mvd folder and select Load settings. To load the monodispersed solution, from
the left side panel, right-click the droplets_mvd → out.droplet solution file and select Load.
Note:
If you closed your Fluent Icing session since the completion of the last tutorial, you must
reopen your project and load your previous simulation and settings. To do this, open
Fluent Icing, select Project → Open..., and navigate to and select your FLUENT_ICING_NACA0012.flprj project file. Once the project is opened, right-click the
naca0012_icing simulation folder, and select Load in solver. The simulation will be
opened, and your window display will switch to the Outline View, with a simulation tree
appearing under naca0012_icing (loaded). Once this is done, continue with step 1.
2. Select Simulation from the top ribbon menu. Select Setup under naca0012_icing (loaded). In its
Properties - Setup window, make sure that Airflow, Particles and Ice are checked.
3. Under Setup → Ice,
• In Ice accretion conditions,
– Check Specify Icing air temperature to simulate an icing temperature that is different than
the reference/far-field air temperature.
– Set the Icing air temperature to 248.15 K (-25 °C).
• In Model,
– Make sure that Icing model is set to Glaze.
• Leave the other settings as default.
4. In general, there is nothing to set in the Boundary Conditions of Ice unless icing is to be turned
off on certain surfaces to reduce computational effort or sink boundaries are to be declared. Examine
the options available at each wall without performing any changes.
5. Go to Solution and inside the Properties - Solution window, change Log verbosity to Complete
to output extra execution and post-processed data in the Console Window.
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Fluent Icing Ice Accretion on the NACA0012
6. Go to the Solution → Ice,
• Under Time, keep the Total time of ice accretion [s] at 420 seconds and the Automatic time
step option checked. The Ice feature in Fluent Icing is an explicit time-accurate code where the
stability of the solution strongly depends on the value of the time step. The automatic time
stepping option calculates the optimal stable time step at every iteration, which can change
greatly depending on the size of the geometry and the mesh density.
7. Right-click Ice under Solution and choose Calculate to run the calculation. A window will appear.
Name the new run ice_mvd_m25C.
8. After the simulation is complete, an ice solution out.swimsol, and ice grid out.ice.grid will
be saved in the ice_mvd_m25C run folder.
Look through the Console window of naca0012_icing. The accumulated time, value of the time
step, total impingement, film, and mass of ice are printed at selected iterations. Heat flux and ice
mass per wall boundary condition are listed in the following two tables. Finally, energy and mass
conservation tables are printed. Most of the items in these tables are self-explanatory except perhaps
mass of clipped film and runback flux. Clipped film refers to any film that is removed by sink
boundaries and on certain nodes which collect and shed water (trailing edges, wing and blade tips,
etc.) that are detected automatically. Runback flux is the sum of all edge fluxes in the domain which
will be equal to the film removed by sink boundaries, or close to zero (mass conservation).
Figure 28.22: Mass Conservation Table Printed in the Log File of Fluent Icing
9. Cycle through the Plots window. By changing the Curve type, you will observe the progress of the
total mass of ice, the change in instantaneous ice growth, water film thickness, and ice surface
temperature with time. Since the input flow and droplet solutions are steady-state solutions, the
icing solutions will eventually reach a steady-state where instantaneous ice growth, water film
thickness, and ice surface temperature do not change after a while.
10. Go to the Ribbon menu and select View. In Quick-view, click Ice cover → Ice over - Viewmerical
to see the ice shape and the original surface in Viewmerical. If a window appears asking if you would
like to append to a previously opened Viewmerical display, choose No.
Alternatively, the ice cover solution can be loaded by going to the Project menu, right-clicking on
the out.swimsol located in the ice_mvd_m25C run and selecting View with Viewmerical. A window
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will appear, select Ice Cover as the view type. If a window appears asking if you would like to append
to a previously opened Viewmerical display, choose No.
You can change the Metallic + Smooth option to other choices in the Object box to see the wireframe profiles and the surface meshes. In the Data panel, you can adjust the Ice thickness threshold
based on ice growth to reduce display interlacing due to the overlapping of iced and clean surfaces.
Figure 28.23: Ice View in Viewmerical Showing Shaded + Wireframe, -25 °C
At -25 °C (248.15 K), the result is a pure rime ice shape.
11. Do not close the Fluent Icing session and run two more calculations at warmer temperatures.
12. In the Outline View panel, select Setup → Ice and, in Ice accretion conditions, check Specify Icing
air temperature and set the Icing air temperature value to 263.15 K (-10 °C).
13. Right-click Ice under Solution and click Calculate to run the calculation. A window will appear
asking if you would like to continue the current run. Choose No. Another window will appear. Name
the new run ice_mvd_m10C.
14. Repeat steps 12 to 13. This time with an Icing air temperature value of 265.67 K (-7.48 °C), same
as the airflow Temperature [K] in Setup → Airflow → Conditions. Name this run ice_mvd_m7p5C.
Note:
This -7.48 °C run is conducted at the same temperature as the airflow simulation. This is
the standard usage of Fluent Icing, and most icing simulations will be run in this manner.
Since the Icing air temperature is equivalent to the airflow simulation temperature, you
can alternatively uncheck Icing air temperature [K] to disable it and Fluent Icing will
use the airflow simulation temperature by default.
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Fluent Icing Ice Accretion on the NACA0012
15. Now that there are 3 different ice shapes computed, we will analyze them using Quick-View. Go
to the Ribbon menu and select View. In Quick-view, click Ice cover → Ice cover – Viewmerical.
This opens the ice solution calculated in the previous simulation.
Figure 28.24: Ice View in Viewmerical Showing Metallic + Smooth, , -7.5 °C
16. Rename this object by double-clicking on its original name in the Object window and enter Ice
-7.5C in the window Rename dataset.
17. To load the -10 °C and -25 °C solutions, go to Project View. Under the run ice_mvd_m10C, rightclick its out.swimsol file and select View with Viewmerical.
18. A message appears asking if you would like to append this solution to a previously opened Viewmerical display. Click Yes.
19. A second message appears asking you to select the view type. In this case, select Ice cover as we
are going to compare the ice shapes produced by our simulations.
20. Inside Viewmerical, rename this new object by double-clicking on its original name in the Object
window and enter Ice - 10C in the window Rename dataset.
21. Repeat steps 17 to 20 for the remaining ice shape, ice_mvd_m25C.
22. Click the Lock button
at the bottom right of the data set list window located in the Objects
panel to enable all the grids in the 2D plot.
23. Go to the Query panel and enable the 2D plot. Change the Cutting plane to Z and Mode to
Geometry. At the bottom left of the 2D Plot window, set the horizontal axis to X. Change the color
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and thickness of the curves by right-clicking on the cube menu on the top right and then by
choosing the Curve Settings menu.
Note:
In this case, since all simulations were executed using a single ice accretion quasi-steady
shot, each *-map curve represents the geometry of the NACA0012.
Figure 28.25: Ice Shapes at -25, -10, and -7.5 C
At -25 °C (248.15 K), the cooling effects are large, and all droplets freeze almost instantly producing
a rime ice shape. This shape generally resembles the original airfoil profile and can be considered
somewhat aerodynamic. As the icing temperature increases, more water can run back away from
the stagnation zone and freeze where cooling effects become more predominant. This mechanism
initiates the growth of ice horns on the upper and lower sides of the airfoil. These geometric features
are common in glaze icing conditions and induce flow separation. Therefore they dramatically change
the aerodynamic performance of the airfoil.
To properly capture the shape of the ice horns, a multishot computation is recommended where
the grid, air and droplet solutions are updated at certain time intervals.
24. Finally, we will compare the film height of the three solutions. To do this, uncheck all Ice* objects
located in the Objects panel of Viewmerical.
25. Go back to the Project View. Under the run ice_mvd_m7p5C, right-click its out.swimsol file and
select View with Viewmerical.
26. A message appears asking if you would like to append this solution to a previously opened Viewmerical display. Click No. A new Viewmerical window will be used to compare the solution values.
27. A second message appears asking you to select the view type. In this case, select Ice solution as
we are going to compare the solution fields of our ice simulations.
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Fluent Icing Ice Accretion on the NACA0012
28. Inside Viewmerical, rename this new object by double-clicking on its original name in the Object
window and enter -7.5C in the window Rename dataset.
29. Repeat steps 25 to 28 for the remaining run folders, ice_mvd_m10C and ice_mvd_m25C. However,
this time select Yes to append these solutions to the previous solution.
30. In the Data panel, inside Files, choose Film Thickness as the Data field. Click Shared inside Color
range.
31. Go to the Query panel and activate the 2D plot. Set the Mode to Data and Cutting plane to Z.
Set the horizontal axis to Y. The three curves showing the film height for the 3 different temperatures
should be visible. Change the curve colors and thickness using the Curve Settings in the cube menu
located at the top right.
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Figure 28.26: Film Height Variation over the Ice at -25, -10, and -7.5 C
The film height and extent grow with increasing icing temperatures. At -25 °C, almost all droplets
freeze upon impact and there is no water runback on the surface. This temperature produces a rime
ice shape. In the contrary, the amount of film and water runback of the other two cases clearly
produce ice horns and form glaze ice shapes.
Note:
The Ice Cover solutions *-map also contain the solution fields of their icing simulations.
You can see their content by clicking on (disabling) -7.5C, -10C and -25C located at the
bottom of the 2D plot of the Query panel. However, it is recommended to use the Ice
Solution mode when post-processing solution fields with Viewmerical as this mode
provides more solution fields capabilities.
Caution:
Do not close Fluent Icing if you would like to proceed to the next section.
28.5. Postprocessing an Ice Accretion Solution Using CFD-Post Macros
In this tutorial, you will learn how to quickly post-process one-shot Ice results (Ice shape and ice solution
fields) using two dedicated CFD-Post macros: Ice Cover – 3D-View and Ice Cover – 2D-Plot. For this
purpose, the icing solution of your icing simulation at -7.5 °C of Fluent Icing Ice Accretion on the
NACA0012 (p. 1065) is used and, therefore, completion of Fluent Icing Ice Accretion on the
NACA0012 (p. 1065) is required.
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Postprocessing an Ice Accretion Solution Using CFD-Post Macros
For more information regarding these macros, consult CFD-Post Macros within the FENSAP-ICE User
Manual.
Note:
CFD-Post only supports .h5 format files when beta features are enabled. Therefore, in order
to ensure full compatibility with CFD-Post, first load CFD-Post, go to Edit → Options. Inside
the Options window, go to CFD-Post → General → Beta Options and check Enable Beta
Features.
1. Inside your Fluent Icing window, go to the Ribbon menu and select View. In Quick-view, click Ice
cover → Ice cover – CFD-Post.
2. After opening CFD-Post, a Domain Selector window will request confirmation to load the following
domains: ice swimsol, map grid, and map swimsol. Click OK to proceed.
3. Go to the Calculators tab and double-click Macro Calculator. The Macro Calculator’s interface
panel will be activated and displayed.
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Note:
The Macro Calculator can also be accessed by selecting Tools → Macro Calculator from
CFD-Post’s main menu.
4. Select the Ice Cover – 3D-View macro script from the Macro drop-down list. This will bring up the
user interface which contains all input parameters required to view ICE3D output solutions in the
CFD-Post 3D Viewer.
5. The default settings inside the Macro Calculator panel will allow you to automatically output the
ice shape of a one-shot icing simulation by pressing Calculate. Figure 28.27: Ice View with CFD-Post,
Ice Cover (p. 1075) shows the output of the default settings of the macro.
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Postprocessing an Ice Accretion Solution Using CFD-Post Macros
Figure 28.27: Ice View with CFD-Post, Ice Cover
Note:
To change the style of the ice shape display, go to the Display Mode and select one of
following options: Ice Cover, Ice Cover – shaded, Ice Cover – No Orig, Ice Cover (only)
or Ice Cover (only) - shaded. To output the surface mesh of the ice shape, go to the
Display Mesh and select Yes. Figure 28.28: Ice View in CFD-Post, Ice Cover with Display
Mesh (p. 1076) shows the output of activating Ice Cover under Display Mode by selecting
Yes under Display Mesh and pressing Calculate at the bottom of the Macro Calculator.
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Figure 28.28: Ice View in CFD-Post, Ice Cover with Display Mesh
6. To display the solution fields of your icing simulation, you can either select Ice Solution – Overlay,
Ice Solution or Surface Solution under Display Mode. In this case, you will output the ice accretion
rate over the ice layer. To do this, select Ice Solution – Overlay in Display Mode, Instant. Ice
Growth (kg s^-1 m^-2) in Display Variable and No in Display Mesh to turn off the displaying
surface mesh.
7. Click Calculate to view the instantaneous ice growth over the ice shape. Figure 28.29: Ice View in
CFD-Post, Instantaneous Ice Growth over Ice Cover Surface (p. 1077) shows the output of the macro.
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Postprocessing an Ice Accretion Solution Using CFD-Post Macros
Figure 28.29: Ice View in CFD-Post, Instantaneous Ice Growth over Ice Cover Surface
Note:
Users are invited to modify the input parameter of Display Variable to view different
fields of the ICE3D solution.
8. You will now explore some quick post-processing capabilities of the Ice Cover – 2D-Plot macro. In
the Macro drop-down list of the Macro Calculator panel, change the macro to Ice Cover – 2D-Plot.
Note:
This switches the macro from Ice Cover – 3D-View to Ice over – 2D-Plot. Switch back
to Ice Cover – 3D-View in the same way if needed.
9. Change Plot’s Title from default, ICE SHAPE PLOT, to Ice Shape at -7.5 C, since you will
be creating a 2D-plot of the ice shape.
10. Inside 2D-Plot (with),
• Set Mode to Geometry to output an ice shape. The other options output the ice solution fields.
• Set Cutting Plane to Z plane. Specify a Z=0 plane by setting X/Y/Z Plane to 0.
• Set the X-Axis to X and the Y-Axis to Y.
11. To center the 2D-Plot around the leading edge of the NACA0012, in 2D-Plot (with),
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• Change the (x)Range of the X-Axis from Global to User Specified. Specify values of 0.075 and
-0.01 in the input boxes of (Usr.Specif.x)Max and (Usr.Specif.x)Min, respectively.
• Change the (y)Range of the Y-Axis from Global to User Specified. Specify values of 0.03 and
-0.03 in the input boxes of (Usr.Specif.y)Max and (Usr.Specif.y)Min, respectively.
12. Leave the other default settings unchanged and click Calculate to create a 2D-Plot of the ice shape
in a floating ChartViewer of CFD-Post. Adjust the output window’s size. Figure 28.30: 2D-Plot in
CFD-Post, Clean Wall Surface and Ice Cover Surface (p. 1078) shows the output of the macro.
Figure 28.30: 2D-Plot in CFD-Post, Clean Wall Surface and Ice Cover Surface
13. To create a 2D-plot of an ice solution field, first change the name of the plot. In this case, enter
Water Film at -7.5 C in the Plot’s Title field since you will create a water film 2D plot along
the thickness of the airfoil.
14. Inside 2D-Plot (with),
• Set Mode to Solution (on Map