CFD Simulations AC1-05
Ahmed body
Application Challenge 1-05 © copyright ERCOFTAC 2004
Overview of CFD Simulations
CFD simulations have developed rapidly during the writing of the present document, during the MOVA consortium and in the frame of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling organized in Darmstad, Germany and Poitiers, France, in 2001 and 2002, respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:
http://www.ercoftac.nl/workshop10/index.html
For the 10th ERCOFTAC-IAHR Workshop, several recommendations were made to the groups participating in the CFD calculations. Among them the recommendation to extend the computational domain up to 5 times the car length downstream of the body, and the possibility to omit the stilts.
Many of the CFD results are considered by the authors themselves as preliminary computations and were therefore not inserted into the knowledge base.
The geometry is simple enough to be satisfactorily represented.
Simulation Case CFD1
Solution strategy CFD1
RANS modelling.
Commercial FLUENT 4.2 code, based on unstructured finite volume discretization.
Reynolds number: 4.29x106 (see EXP1). Steady state computation.
The slant angle is varied from 0 to 50 degrees.
Computational Domain CFD1
Symmetry is used to compute half the domain.
Domain: [-3L;5L]x[0;2L]x[0;2L]
Mesh : 450,000 cells
Approximate value of y+ on solid surfaces : 30.
Boundary Conditions CFD1
Inlet: turbulence level 0.5% with a mixing length of 5x10-3m.
Outlet: constant pressure.
Solid boundaries: wall functions
Symmetry plane: symmetry
Other boundaries: no details
Application of Physical Models CFD1
Standard K-ε model with standard wall functions.
Numerical Accuracy CFD1
Mesh refinement is performed until the drag reaches a constant value.
Convection scheme : 2nd order.
CFD Results CFD1
Friction lines, pressure iso-contours at the model surface, velocity vector fields, drag coefficient.
References CFD1
Modelling of stationnary three-dimensional separated flows around an Ahmed reference model.
P. Gilliéron, F. Chometon, ESAIM proc., vol 7, 173-182, 1999
Simulation Case CFD2
Solution strategy CFD2
RANS modeling.
Commercial FLUENT 5 code based on unstructured finite volume discretization.
Reynolds number: 4.29x106 (see EXP1). Steady state computation.
Slant angle: 30°.
Computational Domain CFD2
Symmetry is used to compute half the domain. Stilts are included.
Domain: no details.
Mesh : 704,000 cells.
y+ at the first grid point from the wall of order of 50 - 350.
Boundary Conditions CFD2
No details.
Application of Physical Models CFD2
- Standard k-ε model with non-equilibrium wall functions.
- RSM (no details) with non-equilibrium wall functions.
Numerical Accuracy CFD2
No details.
CFD Results CFD2
Pathlines and velocities.
Aerodynamic drag coefficient.
References CFD2
Advances in external-aero simulation of ground vehicles using the steady RANS equation.
Makowski F.T and Kim S.E., SAE Conf 2000-01-0484
Simulation Case CFD3
Solution strategy CFD3
Large-eddy simulation.
In house code PRICELES, based on unstructured second-order finite-element discretization.
Reynolds number= 4.29 x106
Slant angle: 28°.
Computational Domain CFD3
Domain: [-3L;5L]x[-L;L]x[-LxL] (the ground plate is NOT included: the body is suspended in the middle of the domain).
Mesh: 1.6x106 cells.
y+ at the first grid point from the wall is about 80 (averaged value).
Boundary Conditions CFD3
Inlet: constant velocity.
Outlet: constant pressure conditions.
Solid boundaries: wall functions
Other boundaries : symmetry.
Application of Physical Models CFD3
Sub-grid model: standard Smagorinsky.
Numerical Accuracy CFD3
Second-order convection scheme and time marching (CFL number=3).
CFD Results CFD3
Pressure, pressure coef., velocity, drag coef, Q-criterion contours, vorticity.
References CFD3
Large eddy simulation of an Ahmed reference model.
R.J.A. Howard, M. Pourquie.
Journal of Turbulence, 2002
Simulation Case CFD4
Solution strategy CFD4
RANS modelling.
Commercial AVL SWIFT code, based on unstructured finite volume discretization.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25° and 35°.
Computational Domain CFD4
Symmetry is used to compute half the domain.
Domain: Inlet at -1.5L. No other details.
Mesh : 530,000 cells.
y+ on solid surfaces < 100.
Boundary Conditions CFD4
Inlet: interpolated experimental profile at –1.4L used at –1.5L.
Solid boundaries: wall functions
Symmetry plane: symmetry
Other boundaries: no details
Application of Physical Models CFD4
- Standard k-ε model with standard wall functions.
- SSG Reynolds stress model with standard wall functions
- Hybrid k-ε/Reynolds stress model (coefficient Cm of the k-ε model obtained from Reynolds stress transport equations) with standard wall functions
Numerical Accuracy CFD4
Grid sensitivity study.
Study of the influence of the convection scheme.
CFD Results CFD4
Cp, velocity profiles in the boundary layer over the slant part.
References CFD4
B. Basara, S. Jakirlic, Flow Around a simplified car body (Ahmed body) : description of numerical methodology, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/IAHR/COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.
Simulation Case CFD5
Solution strategy CFD5
RANS modelling.
In-house code Saturne, based on unstructured finite volume discretization.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25° and 35°.
Computational Domain CFD5
Full body (no symmetry used)
Domain: no details
Mesh : 300,000 cells
y+ on solid surfaces : no details.
Boundary Conditions CFD5
Inlet: no details.
Solid boundaries: wall functions
Other boundaries: no details
Application of Physical Models CFD5
- Standard k-ε model with standard wall functions
- Launder, Reece, Rodi (IP) Reynolds stress model with standard wall functions
- Linearized production k-ε model with standard wall functions
Numerical Accuracy CFD5
Convection scheme : 80% central differencing (2nd order), 20% upwind differencing (1st order).
CFD Results CFD5
Cp, velocity profiles in the boundary layer over the slant part.
Vector plots, turbulent energy contours, streamlines.
References CFD5
S. Tekam, D. Laurence, T. Buchal, Flow around the Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.
Simulation Case CFD6
Solution strategy CFD6
RANS modelling.
Commercial FLUENT code, based on unstructured finite volume discretization.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25°.
Computational Domain CFD6
Domain: no details
Mesh : 2.3x106 cells
y+ on solid surfaces : no details
Boundary Conditions CFD6
Solid boundaries:
- non-equilibrium wall functions for the k-ε model
- no slip walls for the SST model
Inlet, outlet and other boundaries: no details
Application of Physical Models CFD6
- Realizable k-ε model with non-equilibrium wall functions
- SST model
Numerical Accuracy CFD6
No details
CFD Results CFD6
Cp, velocity profiles in the boundary layer over the slant part.
References CFD6
M. Lanfrit, M. Braun, D. Cokljat, Contribution to case 9.4: Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.
Simulation Case CFD7
Solution strategy CFD7
RANS modelling in unsteady mode.
In-house X-Stream code, based on finite volume solver for multi block structured non-orthogonal, curvilinear grid with collocated data arrangement. The convection terms are discretized using hybrid scheme with more than 60% central differencing. The diffusion terms are approximated with central differences. The SIMPLE method is used for the pressure-velocity coupling.
Reynolds number: 2.78x106 (see EXP2).
Slant angle: 35°
Computational Domain CFD7
Full body (no symmetry condition used).
Domain: [-2L;5L]x[-1.2;1.2L]x[0;1.3L]
9th ERCOFTAC workshop: 500,000 cells
10th ERCOFTAC workshop: 2 meshes: 490,000 and 820,000 cells (fine mesh used for the k-ε model only)
Approximate value of y+ on solid surfaces:
- 9th workshop: 60
- 10th workshop: 17 (coarse mesh) and 11 (fine mesh).
Boundary Conditions CFD7
Inlet: turbulence intensity=2,5%
Solid boundaries: wall functions
Outlet: no details
Other boundaries: no details
Application of Physical Models CFD7
9th ERCOFTAC workshop:
- Standard k-ε model with standard wall functions
- SSG Reynolds stress model with standard wall functions
- SSS Reynolds stress model with non-equilibrium wall functions
- V2F model with wall functions
- Elliptic blending model (Reynolds stress model) with wall functions
10th ERCOFTAC workshop:
- Standard k-ε model with wall functions
- V2F model with wall functions
- SSG Reynolds stress model with modified ε equation (Hanjalic, Jakirlic) and standard wall functions
Numerical Accuracy CFD7
Convection scheme : 60% 2nd order central differencing, 40% 1st order upwind differencing.
CFD Results CFD7
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
References CFD7'
O. Ouhlous, W. Khier, Y. Liu, K. Hanjalic, in: S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.
M. Hadziabdic, K. Hanjalic, W. Khier, Y. Liu, O. Ouhlous, Flow around a simplified car body (Ahmed car model), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.
Simulation Case CFD8
Solution strategy CFD8
RANS modelling.
In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie & Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25° and 35°.
Computational Domain CFD8
Symmetry is used to compute half the domain. Stilts not included.
Domain: [-2L;4L]x[0;L]x[0;L]
Mesh : 300,000 cells
Approximate value of y+ on solid surfaces : between 55 and 550.
Boundary Conditions CFD8
Inlet:
- U=38.51 m/s (based on the experimental profile at –1.4L in order to account for the flow deceleration in front of the body)
- K=6.58x10-3 m2 s-2
- nt/n=10 (influence tested)
Outflow: zero gradients for all variables
Solid boundaries: wall functions
Symmetry plane: symmetry
Other boundaries: symmetry
Application of Physical Models CFD8
- Standard k-ε model with Yap correction and SCL wall functions (see below)
- Standard k-ε model with Yap correction and UMIST-N wall functions
- Linear realizable k-ε model with SCL wall functions
- Linear realizable k-ε model with UMIST-A wall functions
- Nonlinear k-ε model (Craft et al.) with SCL wall functions
- Nonlinear k-ε model (Craft et al.) with UMIST-A wall functions
Wall functions:
- SCL = Simplified Chieng and Launder
- UMIST-A = UMIST Analytical
- UMIST-N = UMIST Numerical
Numerical Accuracy CFD8
Convection scheme : 3rd order Quick scheme (UMIST) or 1st order upwind scheme in case of numerical instability.
Tests were made to assess iteration convergence. Some unsteady calculations were made too. A coarser grid was used to obtain some information on grid dependency.
CFD Results CFD8
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
References CFD8
T.J. Craft, S.E. Gant, H. Iacovides, B.E. Launder, C.M.E. Robinson, Computational methods applied to the study of flow around a simplified “Ahmed” car body, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.
Simulation Case CFD9
Solution strategy CFD9
LES.
In-house code LESOCC2, based on block-structured finite volume discretization. A collocated cell arrangement was used employing the Rhie and Chow momentum interpolation procedure. The SIMPLE scheme was used for the pressure-velocity coupling, and the pressure correction equation was solved using the SIP method. Fluxes were discretized in space using a second order central difference scheme. The equations were integrated in time using a second order Runge Kutta scheme with an adaptive time step, employing a maximum CFL number of 0.6.
Reynolds number: 2.78x106 (see EXP2).
Slant angle: 25°.
Computational Domain CFD9
Domain: [-2.2L;4.8L]x[-0.9L;0.9L]x[0;1.35L]. Ground plate and stilts included.
Mesh :18.5x106 cells
y+ on solid surfaces : no details
Boundary Conditions CFD9
Inlet: constant velocity
Outlet: convective outlet.
Solid boundaries: wall functions
Other boundaries: slip walls
Application of Physical Models CFD9
Subgrid scale model: Smagorinky
Numerical Accuracy CFD9
2nd order convection scheme and time marching (CFL number < 0.6)
CFD Results CFD9
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
References CFD9
C. Hinterberger, M. Garcia-Villalba, W. Rodi, Flow around a simplified car body. LES with wall functions, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.
Simulation Case CFD10
Solution strategy CFD10
RANS modelling.
Commercial HEXANS CFD code, based on unstructured finite volume discretization. The convective fluxes are discretized using a centered scheme with 2nd and 4th order artificial dissipation. Diffusive fluxes are computed on pyramidal elements. The equations are integrated in time using the explicit Runge Kutta scheme. Local time stepping, multi grid and low-mach number preconditioning are used to accelerate the convergence to steady state. A mesh adaptation procedure is used in which the grid cells are refined by splitting it in 2, 4 or 8 subcells. The mesh adaptation is governed by criteria based on the flow physics, geometry or error estimates.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25°.
Computational Domain CFD10
Symmetry is used to compute half the domain. Ground plate included, no stilts.
Domain: [-2L;5L]x[0;0.9L]x[0;1.35L]
Final Mesh : 815,000 cells
Approximate value of y+ on solid surfaces : 1
Boundary Conditions CFD10
Inflow: turbulence level 1%. nt/n = 1.
Solid boundaries: no-slip walls
Symmetry plane: symmetry
Other boundaries: no details
Application of Physical Models CFD10
Low-Reynolds number K-ε model (Yang-Shih).
Numerical Accuracy CFD10
Mesh adaptation applied.
Convection scheme : 2nd order.
CFD Results CFD10
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
References CFD10
B. Leonard, Ch. Hirsch, K. Kovalev, M. Elsden, K. Hillewaert, A. Patel, Flow around a simplified car body (Ahmed body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.
Simulation Case CFD11
Solution strategy CFD11
RANS modelling.
Commercial CFX-5 code, based on an unstructured, vertex based finite volume method. Co-located variables are used. The solver is second order accurate in space and time. The Rhie-Chow velocity pressure coupling is used. An implicit solver with algebraic multi grid is used to converge the equations to steady state.
Reynolds number: 2.78x106 (see EXP2). Transient computation (steady solution obtained).
Slant angle: 25° and 35°.
Computational Domain CFD11
Symmetry is used to compute half the domain. No stilts included.
Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]
The ground plate starts 2L in front of the body in order that the boundary layer approaching the body matches the experimental profile.
Mesh : 2,5x106 cells
Approximate value of y+ on solid surfaces : 1
Boundary Conditions CFD11
Inlet: turbulence intensity=1%, nt/n=1.
Solid boundaries:
- SST model: no slip walls
- Others: scalable wall functions
Outlet: constant pressure
Other boundaries: opening boundary conditions.
Application of Physical Models CFD11
- Standard k-ε model with scalable wall functions
- SST model
- SSG Reynolds stress model with scalable wall functions
Numerical Accuracy CFD11
Convection scheme: 2nd order.
Studies of the influence of the following parameters are performed:
Mesh refinement, formulation of the boundary conditions (opening vs. slip walls), advection scheme.
CFD Results CFD11
The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses in some planes and profiles in the boundary layer above the slant part:
k-epsilon model
25° slant angle:
x=-794; x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
35° slant angle:
x=-794; x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
SST model
25° slant angle:
x=-794; x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
35° slant angle: planes: y=0; y=100; y=180;
y=195; z=360
x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
References CFD11
L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body (synopsis), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.
L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body, CFX Validation report (florian.menter@ansys.com)
Simulation Case CFD12
Solution strategy CFD12
RANS modelling.
In-house code CFL3D, compressible flow solver employing multi block structured grids. An upwind finite volume formulation is used for the space discretization. An implicit approximate factorization method is used to integrate the equations in time. Local time stepping, grid sequencing, multi grid and low Mach number preconditioning are used to accelerate convergence to steady state.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25° and 35°.
Computational Domain CFD12
Symmetry is used to compute half the domain. No stilts included.
Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]
Mesh : 1.3x106 cells
Approximate value of y+ on solid surfaces : 1.5
Boundary Conditions CFD12
Inlet: no details
Solid boundaries: no-slip walls
Symmetry plane: symmetry
Other boundaries: farfield Riemann-invariant conditions
Application of Physical Models CFD12
- SST model
- Explicit Algebraic Stress Model with ω-equation
Numerical Accuracy CFD12
Convection scheme : 1st order.
CFD Results CFD12
The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses in some planes and profiles in the boundary layer above the slant part:
SST model
25° slant angle:
x=-794; x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
35° slant angle:
x=-794; x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
EASM model
25° slant angle:
x=-794; x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
35° slant angle:
x=-794; x=-178; x=-138; x=-88; x=-38; x=0; x=80; x=200; x=500
profiles in the boundary layer: x=-243, -223, -203, -183, -163, -143, -123, -103, -83, -63, -43, -23, -3
Pressure coefficients on the rear of the body: Cp
References CFD12
C.L. Rumsey, Application of CFL3D to case 9.4 (Ahmed Body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.
Simulation Case CFD13
Solution strategy CFD13
RANS modelling.
In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie & Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25°.
Computational Domain CFD13
Symmetry is used to compute half the domain. No stilts included.
Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]
Mesh : 1.3x106 cells
Approximate value of y+ on solid surfaces : 1
Boundary Conditions CFD13
Inlet: no details
Solid boundaries: no-slip walls
Other boundaries: symmetry
'Application of Physical Models CFD13
All are low-Reynolds number models
- Linear k-ε model (Launder-Sharma)
- Linear k-ω model (Wilcox)
- Cubic k-ε model (Apsley, Leschziner)
- Quadratic k-ω model (Abe, Jang, Leschziner)
- Quadratic k-ε model (Abe, Jang, Leschziner)
- SSG + Chen (Abe, Jang, Leschziner)
Numerical Accuracy CFD13
No details
CFD Results CFD13
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
References CFD13
Y.J. Jang, M. Leschziner, Contribution of Imperial College to Test Case 9.4: Flow around a simplified car body, In: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.
Simulation Case CFD14
Solution strategy CFD14
RANS modelling.
In-house code ISIS, based on unstructured finite volume discretization.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25° and 35°.
Computational Domain CFD14
Symmetry is used to compute half the domain.
Domain: [-4L;5L]x[0;0.9L]x[0;1.35L]
Mesh : 3.8x106 cells
Approximate value of y+ on solid surfaces: 0.5
Boundary Conditions CFD14
Solid boundaries: no slip wall
Symmetry plane: symmetry
Other boundaries: no details
Application of Physical Models CFD14
SST model
Numerical Accuracy CFD14
No details
CFD Results CFD14
Velocity profiles in the boundary layer over the slant part, streamlines, turbulent energy contours.
References CFD14
E. Guilmineau, Numerical simulation of flow around a simplified car body, Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA
Simulation Case CFD15
Solution strategy CFD15
RANS modelling.
Commercial StarCD code, based on unstructured finite volume discretization.
Reynolds number: 2.78x106 (see EXP2). Steady state computation.
Slant angle: 25°.
Computational Domain CFD15
Symmetry is used to compute half the domain. No stilts included. The ground plate starts 2L upstream of the body in order to reproduce the experimental boundary layer.
Domain: [-5.75L;5.75L]x[0;L]x[0;1.35L]
Mesh : 1.6x106 cells
Approximate value of y+ on solid surfaces : < 3
Boundary Conditions CFD15
Inlet: turbulence level 0.1%, nt/n=10.
Outlet: convective outlet.
Solid boundaries: no-slip walls
Symmetry plane: symmetry
Other boundaries: symmetry
Application of Physical Models CFD15
Rescaled V2F model (Manceau, Carlson, Gatski)
Numerical Accuracy CFD15
No details.
CFD Results CFD15
Vector plots.
References CFD15
R. Manceau, Computation of the flow around a simplified car using the rescaled v2f model, Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA
NAME | Re x 10^{-6} | Slant angle (degrees) | SPs | |
---|---|---|---|---|
Detailed Data | DOAP | |||
CFD1 | 4.29 | 0, 10, 12, 20, 25, 30, 40, 50 | Pressure Tomographies | C_{d}, Streamlines, Friction Lines |
CFD2 | 4.29 | 30 | Effective Viscosity | C_{D}, Velocities |
CFD3 | 4.29 | 28 | Pressure Coefficient, Q-criterion Contours | C_{d}, Velocities, Vorticity Contours |
CFD4 | 2.78 | 25, 35 | C_{P} | Velocity Profiles |
CFD5 | 2.78 | 25, 35 | C_{P}, Turbulent Energy Contours | Velocity Profiles, Vector Plots, Streamlines |
CFD6 | 2.78 | 25 | C_{P} | Velocity Profiles |
CFD7 | 2.78 | 35 | C_{P} | Velocity Profiles, Vector Plots |
CFD8 | 2.78 | 25, 35 | C_{P} | Velocity Profiles, Vector Plots |
CFD9 | 2.78 | 25, 35 | C_{P} | Velocity Profiles, Vector Plots |
CFD10 | 2.78 | 25 | C_{P} | Velocity Profiles, Vector Plots |
CFD11 | 2.78 | 35 | C_{P} | C_{d}, Velocity Profiles, Vector Plots |
CFD12 | 2.78 | 25, 35 | C_{P} | Velocity Profiles, Vector Plots |
CFD13 | 2.78 | 25 | C_{P} | Velocity Profiles, Vector Plots |
CFD14 | 2.78 | 25, 35 | Turbulent Energy Contours | Velocity Profiles, Streamlines |
CFD15 | 2.78 | 25 | Vector Plots |
Simulation Case CFD16 (added in 2024 by F.R. Menter)
Solution Strategy CFD16
Large Eddy Simulation – Several simulations using different wall treatments and different meshes.
Commercial Fluent and Fluent-GPU codes
Reynolds number 2.78e6 (EXP2) (also simulations for lower Re=0.72e6)
Slant angle 25°
Computational Domain CFD16
All geometry included.
Domain [m] [-3,6] x [-3,3] x [0, 3.5]
Meshes from 7e6 to 560e6. (given in reference)
Y+ values varying for different meshes (wall-resolved to wall function meshes)
Boundary Conditions CFD16
Inlet – Velocity constant
Bottom wind tunnel wall: non-slip
Other wind tunnel walls: Slip walls
Outlet: Pressure outlet
Application of Physical Models CFD16
(described in Fluent Manual A.F.U. R-22.1, 2022)
WALE model
Wall-Resolved LES
Wall-Function LES
Numerical Accuracy CFD16
2nd order code
Wide range of meshes (given in reference)
CFD Results CFD16
Wall shear stress on the roof-center plane, velocity and streamwise fluctuation profiles on the slant, wall streamlines on the slant, turbulent structures around the car body.
References CFD16
Menter, F.R., Hüppe, A., Flad, D. et al. Large Eddy Simulations for the Ahmed Car at 25° Slant Angle at Different Reynolds Numbers. Flow Turbulence Combust 112, 321–343 (2024).
© copyright ERCOFTAC 2004
Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. — Update (2024) F.R.Menter, ANSYS Germany ,
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