Computational Fluid Dynamics Simulation of
Hypersonic Engine Components
by
Jack R. Edwards
Associate Professor
Department of Mechanical and Aerospace Engineering
North Carolina State University, Raleigh, NC
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Overview
 Computational fluid dynamics simulation of hypersonic engine
components – a major research thrust area in Aerospace Engineering at
NCSU since the Mid 1980s.
 Current areas of emphasis:
• Nose-to-tail simulations of complete engine flowfields (NASA
Glenn; Edwards and McRae)
• Modeling of turbulent Schmidt number and Prandtl number effects
in supersonic combustion (NASA Langley; Hassan and Edwards)
• Modeling of supercritical-fluid and barbotage injection of
hydrocarbon fuels (AFRL/PRA; Edwards)
• Algorithmic enhancements to NASA’s VULCAN flow solver
(NASA Langley; Edwards and McRae)
• Hybrid large-eddy / Reynolds-averaged modeling of scramjet
component flowfields (NIA Seed Grant; Edwards)
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Personnel
 Dr. Jack R. Edwards, Associate Professor
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CFD algorithm development for reacting / multi-phase flows
 Dr. Hassan A. Hassan, Professor
• Transition and Turbulence Modeling
 Dr. D. Scott McRae, Professor
• Solution Adaptive Gridding Methods
 Jason Norris, Keith McDaniel, Ming Tian: Ph.D. students
 Ana Pinto, Michael Schoen: M.S. students
 Adam Amar: Undergraduate research assistant
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Unique Contributions
 Low-Diffusion Flux-Splitting Schemes (LDFSS)
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High-resolution upwind-differencing methods
Extensions for real fluids, gas-solid flows, multi-phase mixture
flows, chemically reacting flows, etc
Several parallel, multi-block, implicit flow solvers built around
LDFSS techniques
 k- Transition / Turbulence Models
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Coordinate-invariant two-equation model for wall-bounded and
free-shear flows at all speeds
Transition model accounts for Tollmein-Schlicting, crossflow,
bypass, and second-mode disturbance growth
Predicts onset and extent of transition and has been coupled with
the Spalart-Allmaras and the k- model
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Unique Contributions
 Dynamic Solution-Adaptive Gridding Techniques
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Improved feature resolution through point-clustering
Extensions for time-accurate flows, multi-block grids with noncontiguous interfaces, unstructured grids
Recent applications to high-speed inlet unstart and pollutant source
tracking in air-quality models
 Hybrid Large-Eddy / Reynolds-Averaged (LES/RANS)
Simulation methods
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Techniques combine RANS strategies near solid surfaces with LES
strategies further away
Transition facilitated by flow-dependent blending functions
Applications to shock / boundary layer interactions in internal
flows
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Resources
 NCSC IBM SP-2 (720 processors, 1 teraflop; soon to be
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replaced with a linux Beowulf cluster)
4-processor Compaq ES-40
2-processor Microway DS-20
1-processor Compaq XP-1000
Several Sun, SGI workstations
Several PCs
LaTEX, Tecplot, Ensight, animation software
VULCAN (NASA Langley), CHEM3D (Dow Chemical)
REACTMB variants (NCSU)
All codes parallelizable with MPI message-passing
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High-Speed Propulsion
 Time-dependent simulations of Scramjet inlet / isolator /
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combustor interactions
Nose-to-tail simulations of NASA Glenn’s GTX RocketBased Combined-Cycle engine concept
Addition of time-derivative preconditioning and parallel
implicit schemes to NASA’s VULCAN flow solver
Simulation of injection of supercritical fuels
Simulation of aerated-liquid injection of hydrocarbon
fuels (Barbotage)
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Independent Ramjet Stream Cycle in RBCC Engines
Fuel injection and
premixing
Flame Front
Thermal Throat
Rocket exhaust
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Injectors add fuel to the incoming air.
Mixing in ramjet stream precedes ignition.
Thermal throat is present.
Location of thermal throat can be modulated by variations in fuel injection.
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Rocket-Based Combined-Cycle Simulations
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Rocket-Based Combined-Cycle Simulations
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Rocket-Based Combined-Cycle Simulations: Rocket-shutoff with
Nitrogen Purge
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Aerated-liquid (Barbotage) injection experiments
 The Air Force Research Lab
(AFRL) aerated-liquid injector is
schematically illustrated in Fig. 01;
 Rectangular configuration with a
dimension of 6.4 mm x 2.0 mm;
 A square cross section with
dimension, D, of 2.0 mm used for
the final discharge passage,
L/D=20, converging angle θ=50°;
 Water as the test liquid, and
nitrogen as the aerating gas.
Fig. 01, Schematic of the injector assembly
and internal flow structure
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Volume fraction contours (GLR = 0.08%)
Bernoulli inflow B.C. for the liquid phase
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GLR=2.45% Photos and simulations
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Hybrid LES/RANS Simulation Techniques
 General approach: unsteady RANS (Reynolds-Averaged Navier-
Stokes) near solid surfaces – LES (large-eddy simulation) in outer part
of the boundary layer and in free-shear layers
 Transition between RANS / LES based on flow-dependent blending
functions based on ratios of turbulence length scales – best results
when transition occurs in outer part of log layer
 RANS models: k- and Menter’s k-
 LES subgrid model: Yoshizawa’s one-equation SGS model
 Applications to cavity flameholder configurations, flow behind
projectiles, shock / boundary layer interactions
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Hybrid LES/RANS Simulation Techniques
Instantaneous axial velocity (25 degree compression / expansion
corner)
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Hybrid LES/RANS Simulation Techniques
EXP
Hybrid (k-, F=F3, fine grid)
Hybrid (k-, F=F3, coarse grid)
RANS (k-)
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4.5
4
0.6
x' = 1.25 cm
3.5
pw/p
Exp
Hybrid (k-, F=F3, fine grid)
Hybrid (k-, F=F3, coarse grid)
RANS (k-)
2.35 cm
3.10 cm
0.5
3
0.4
y', cm
2.5
2
1.5
0.2
1
0.5
0.3
0.1
-5
0
5
x', cm
Wall pressure distributions (25
degree compression/ expansion
corner)
00
1
1
1
u/ue
Velocity profiles in recovery
region (25 degree compression /
expansion corner)
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NIA-Sponsored Work
Primary Goal: to extend earlier work in hybrid LES/RANS simulations to
three-dimensional flows characteristic of dual-mode scramjet engines
Year 1 accomplishments
• Addition of generalized multi-block capability to hybrid LES/RANS
solver
• Addition of full reactive-flow capability
• Development of better blending functions to shift modeling from
unsteady RANS to LES
Test cases underway:
• Investigation of separation-shock unsteadiness in compression-corner
interactions
• Simulation of reactive flow downstream of UVA single-ramp, dualmode injector using hybrid LES/RANS
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NIA-Sponsored Work: Separation-Shock Unsteadiness
 Prediction of response of turbulent boundary layer to shock interaction
(representative of high-speed flows within inlet / isolator configurations)
Large-scale, low-frequency unsteadiness of regions of shock-separated
flow observed in experiments
Can hybrid LES/RANS methods predict this type of unsteadiness?
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NIA-Sponsored Work: Separation-Shock Unsteadiness
Time-dependent surface pressure contours
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NIA-Sponsored Work: Separation-Shock Unsteadiness
Average surface pressure distributions
PDF of separation-shock position
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Leveraging NIA-Sponsored Work
 “Hybrid LES/RANS Simulations of Complex Internal Flows with
Multiple Shock / Boundary Layer Interactions” Edwards and Hassan;
AFOSR; pending
 “Database and Model Development for Combined-Cycle Mode
Transition” McDaniel, Cresci, Edwards, Goyne, O’Brian, Riggins,
Schetz; NASA NGLTP; pending (submitted by NIA)
 MURI White Paper on Combined Cycle Engines, Frankel, Edwards,
McDaniel, Goyne, Hanson, Sung, Dutton, Loth; AFOSR; pending
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Challenges
 Demise of North Carolina Supercomputing Center (July 1, 2003) –
loss of 720 processor IBM SP-3
 Mitigation strategies:
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32 processor IBM P690 (NCSU)
32 processor IBM Bladecenter (NCSU)
128 processor IBM Bladecenter (NCSU; under construction;
expandable)
Access to 1024 processor IBM SP-3 at Oak Ridge National
Laboratories
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Simulation of a time-dependent coatings process
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Pollutant Capture in Circulating Fluidized Beds
 Three-phase system: two solids phases, one multi-
component gas phase
 Sub-models for fine particulate matter agglomeration,
sulfur dioxide sorption, mercury capture onto activated
carbon
 High-resolution LDFSS extension for separated gas-solid
flows
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Solids voidage time evolution
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Fine PM number density time evolution
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Fine PM flow rates
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Supercavitating water flow about a projectile
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New Directions
 Atmospheric turbulence modeling and solution-adaptive
meteorological simulations
 Level-set methods and immersed-boundary algorithms
• Human-induced contaminant transport
• Diesel engine injector simulations
• Two-phase bubble dynamics
 Hybrid LES/RANS simulations of
• Shock-train propagation
• Ramped-injector flowfields
• Biological systems (lung bronchii, aortic aneurisms)
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Level-Set / Immersed Boundary Methods: 2-D
Simulation of “feet” moving in a box filled with air
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