Compressible flow around airfoil
Gambit:
1) Read the file airfoil.dbs into gambit
2) Mesh the airfoil with 200 vertices (100 vertices at top and bottom each). Use a stretching factor of
1.01. Vertices are stretched towards the leading edge.
3) Mesh the edge leaving the airfoil with 100 cells applying a stretching factor of 0.96
4) Attach a boundary layer mesh to the airfoil (Algorithm: uniform, first cell: 0.0004, growth factor: 1.4,
number of rows: 10).
5) Attach a boundary layer mesh to the edge leaving the airfoil (Algorithm: aspect ratio, first cell %: 2,
growth factor 1.4, number of rows: 10)
6) Attach a size function to the left face (Type: meshed, attach to face, source: airfoil edge, growth factor
1.1, maximum: large number that cannot be reached).
7) Attach a size function to both right faces (Type: meshed, attach to face, source: edge leaving the
airfoil, growth factor 1.1, maximum: large number that cannot be reached).
8) Mesh all faces with triangular elements
9) Specify the boundary conditions: pressure far field at the outside boundaries, wall for the airfoil
10) Export the mesh
Fluent:
1) Read the mesh file
2) Switch on the density based solver (define/models)
3) Enable the energy equation (define/models). Temperature has to be computed since the ideal gas law
will be used.
4) Enable the Spalart-Allmaras turbulence model.
5) Use the ideal gas law to compute the density of air (define/materials)
6) The operating condition is 1 atm = 101325 Pa.
7) Set the boundary conditions at the far field: Gauge pressure 0, Temperature 300K, Mach 0.8, angle of
attack: 40, turbulent viscosity ratio: 10. For external flow in free air use value between 1 and 10.
8) Use second order accuracy for the solver settings (solve/controls)
9) Plot the residuals (solve/monitor/residuals)
10) Initialize the flowfield with the values computed from the farfield.
11) Report the lift and drag coefficient during convergence (solve/monitor/force). Take into account that
the freestream velocity in not parallel to the x-axis. The drag force is in the direction of the freestream
velocity. The lift is the force on the airfoil normal to it. In 'reports' set the reference value of the
velocity to the freestream velocity.
12) Iterate until convergence
13) Visualize the flowfield (Contours of Mach number, pressure, temperature; velocity vectors; plot the y+
distribution on the airfoil. It should be either in the viscous subrange: u+ < 5 or in the log-layer: 30 <
y+ < 200).
14) Adapt the grid with the pressure gradient. Compute first the limits. Specify the limit for refining the
grid. Use 'Mark' to select the number of cells. Check if this number is not too large (around 100).
Apply with the 'adapt' button. Repeat this twice.
15) Check the refined grid.
16) Compute the solution on the refined grid.
17) Repeat from step 12.
18) Compute the actual forces on the airfoil (report/forces)