CFD Simulations AC1-05: Difference between revisions

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(New page: ='''Ahmed body'''= '''Application Challenge 1-05''' © copyright ERCOFTAC 2004 =='''Overview of CFD Simulations'''== CFD simulations have developed rapidly during the w...)
 
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='''Ahmed body'''=
='''Ahmed body'''=


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The geometry is simple enough to be satisfactorily represented.
The geometry is simple enough to be satisfactorily represented.
© ERCOFTAC 2004
 
Simulation Case CFD1
 
© ERCOFTAC 2004
=='''Simulation Case CFD1'''==
Solution strategy CFD1
 
==='''Solution strategy CFD1'''===


RANS modelling.
RANS modelling.
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The slant angle is varied from 0 to 50 degrees.
The slant angle is varied from 0 to 50 degrees.
© ERCOFTAC 2004
 
Computational Domain CFD1
 
==='''Computational Domain CFD1'''===


Symmetry is used to compute half the domain.
Symmetry is used to compute half the domain.
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Approximate value of y+ on solid surfaces : 30.
Approximate value of y+ on solid surfaces : 30.
© ERCOFTAC 2004
 
Boundary Conditions CFD1
 
==='''Boundary Conditions CFD1'''===


Inlet: turbulence level 0.5% with a mixing length of 5x10-3m.
Inlet: turbulence level 0.5% with a mixing length of 5x10-3m.
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Other boundaries: no details
Other boundaries: no details
© ERCOFTAC 2004
 
Application of Physical Models CFD1
 
==='''Application of Physical Models CFD1'''===


Standard K-ε model with standard wall functions.
Standard K-ε model with standard wall functions.
© ERCOFTAC 2004
 
Numerical Accuracy CFD1
 
==='''Numerical Accuracy CFD1'''===


Mesh refinement is performed until the drag reaches a constant value.
Mesh refinement is performed until the drag reaches a constant value.


Convection scheme : 2nd order.
Convection scheme : 2nd order.
© ERCOFTAC 2004
 
CFD Results CFD1
 
==='''CFD Results CFD1'''===


Friction lines, pressure iso-contours at the model surface, velocity vector fields, drag coefficient.
Friction lines, pressure iso-contours at the model surface, velocity vector fields, drag coefficient.
© ERCOFTAC 2004
References CFD1


Modelling of stationnary three-dimensional separated flows around an Ahmed reference model.
=='''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
P. Gilliéron, F. Chometon, ESAIM proc., vol 7, 173-182, 1999
© ERCOFTAC 2004
 
Simulation Case CFD2
 
© ERCOFTAC 2004
=='''Simulation Case CFD2'''==
Solution strategy CFD2
 
==='''Solution strategy CFD2'''===


RANS modeling.
RANS modeling.
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Slant angle: 30°.
Slant angle: 30°.
© ERCOFTAC 2004
 
Computational Domain CFD2
==='''Computational Domain CFD2'''===


Symmetry is used to compute half the domain. Stilts are included.
Symmetry is used to compute half the domain. Stilts are included.
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y+ at the first grid point from the wall of order of 50 - 350.
y+ at the first grid point from the wall of order of 50 - 350.
© ERCOFTAC 2004
 
Boundary Conditions CFD2
==='''Boundary Conditions CFD2'''===


No details.
No details.
© ERCOFTAC 2004
 
Application of Physical Models CFD2
==='''Application of Physical Models CFD2'''===


- Standard k-ε model with non-equilibrium wall functions.
- Standard k-ε model with non-equilibrium wall functions.


- RSM (no details) with non-equilibrium wall functions.
- RSM (no details) with non-equilibrium wall functions.
© ERCOFTAC 2004
 
Numerical Accuracy CFD2
==='''Numerical Accuracy CFD2'''===


No details.
No details.
© ERCOFTAC 2004
 
CFD Results CFD2
==='''CFD Results CFD2'''===


Pathlines and velocities.
Pathlines and velocities.


Aerodynamic drag coefficient.
Aerodynamic drag coefficient.
© ERCOFTAC 2004
 
References CFD2
=='''References CFD2'''==


Advances in external-aero simulation of ground vehicles using the steady RANS equation.
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
Makowski F.T and Kim S.E., SAE Conf 2000-01-0484
© ERCOFTAC 2004
Simulation Case CFD3
© ERCOFTAC 2004
Solution strategy CFD3


Large-eddy simulation.
 
=='''Simulation Case CFD3'''==
 
==='''Solution strategy CFD3'''===
 
'''Large-eddy simulation.'''


In house code PRICELES, based on unstructured second-order finite-element discretization.
In house code PRICELES, based on unstructured second-order finite-element discretization.
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Slant angle: 28°.
Slant angle: 28°.
© ERCOFTAC 2004
 
Computational Domain CFD3
==='''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).
Domain: [-3L;5L]x[-L;L]x[-LxL] (the ground plate is NOT included: the body is suspended in the middle of the domain).
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y+ at the first grid point from the wall is about 80 (averaged value).
y+ at the first grid point from the wall is about 80 (averaged value).
© ERCOFTAC 2004
 
Boundary Conditions CFD3
==='''Boundary Conditions CFD3'''===


Inlet: constant velocity.
Inlet: constant velocity.
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Other boundaries : symmetry.
Other boundaries : symmetry.
© ERCOFTAC 2004
 
Application of Physical Models CFD3
==='''Application of Physical Models CFD3'''===


Sub-grid model: standard Smagorinsky.
Sub-grid model: standard Smagorinsky.
© ERCOFTAC 2004
 
Numerical Accuracy CFD3
==='''Numerical Accuracy CFD3'''===


Second-order convection scheme and time marching (CFL number=3).
Second-order convection scheme and time marching (CFL number=3).
© ERCOFTAC 2004
CFD Results CFD3


Pressure, pressure coef., velocity, drag coef, Q-criterion contours, vorticity.
==='''CFD Results CFD3'''===
© ERCOFTAC 2004
 
References CFD3
'''Pressure, pressure coef., velocity, drag coef, Q-criterion contours, vorticity.'''
 
=='''References CFD3'''==


Large eddy simulation of an Ahmed reference model.
Large eddy simulation of an Ahmed reference model.
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Journal of Turbulence, 2002
Journal of Turbulence, 2002
© ERCOFTAC 2004
 
Simulation Case CFD4
 
© ERCOFTAC 2004
=='''Simulation Case CFD4'''==
Solution strategy CFD4
 
==='''Solution strategy CFD4'''===


RANS modelling.
RANS modelling.
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Slant angle: 25° and 35°.
Slant angle: 25° and 35°.
© ERCOFTAC 2004
 
Computational Domain CFD4
==='''Computational Domain CFD4'''===


Symmetry is used to compute half the domain.
Symmetry is used to compute half the domain.
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y+ on solid surfaces < 100.
y+ on solid surfaces < 100.
© ERCOFTAC 2004
 
Boundary Conditions CFD4
==='''Boundary Conditions CFD4'''===


Inlet: interpolated experimental profile at –1.4L used at –1.5L.
Inlet: interpolated experimental profile at –1.4L used at –1.5L.
Line 201: Line 209:


Other boundaries: no details
Other boundaries: no details
© ERCOFTAC 2004
 
Application of Physical Models CFD4
==='''Application of Physical Models CFD4'''===


-        Standard k-ε model with standard wall functions.
-        Standard k-ε model with standard wall functions.
Line 209: Line 217:


-        Hybrid k-ε/Reynolds stress model (coefficient Cm of the k-ε model obtained from Reynolds stress transport equations) 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
© ERCOFTAC 2004
 
Numerical Accuracy CFD4
==='''Numerical Accuracy CFD4'''===


Grid sensitivity study.
Grid sensitivity study.


Study of the influence of the convection scheme.
Study of the influence of the convection scheme.
© ERCOFTAC 2004
 
CFD Results CFD4
==='''CFD Results CFD4'''===


Cp, velocity profiles in the boundary layer over the slant part.
Cp, velocity profiles in the boundary layer over the slant part.
© ERCOFTAC 2004
 
References CFD4
=='''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.
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.
© ERCOFTAC 2004
 
Simulation Case CFD5
 
© ERCOFTAC 2004
=='''Simulation Case CFD5'''==
Solution strategy CFD5
 
==='''Solution strategy CFD5'''==


RANS modelling.
RANS modelling.
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Slant angle: 25° and 35°.
Slant angle: 25° and 35°.
© ERCOFTAC 2004
 
Computational Domain CFD5
==='''Computational Domain CFD5'''===


Full body (no symmetry used)
Full body (no symmetry used)
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y+ on solid surfaces : no details.
y+ on solid surfaces : no details.
© ERCOFTAC 2004
 
Boundary Conditions CFD5
==='''Boundary Conditions CFD5'''===


Inlet: no details.
Inlet: no details.
Line 253: Line 262:


Other boundaries: no details
Other boundaries: no details
© ERCOFTAC 2004
 
Application of Physical Models CFD5
==='''Application of Physical Models CFD5'''===


-        Standard k-ε model with standard wall functions
-        Standard k-ε model with standard wall functions
Line 261: Line 270:


-        Linearized production k-ε model with standard wall functions
-        Linearized production k-ε model with standard wall functions
© ERCOFTAC 2004
 
Numerical Accuracy CFD5
 
==='''Numerical Accuracy CFD5'''===


Convection scheme : 80% central differencing (2nd order), 20% upwind differencing (1st order).
Convection scheme : 80% central differencing (2nd order), 20% upwind differencing (1st order).
© ERCOFTAC 2004
 
CFD Results CFD5
==='''CFD Results CFD5'''===


Cp, velocity profiles in the boundary layer over the slant part.
Cp, velocity profiles in the boundary layer over the slant part.


Vector plots, turbulent energy contours, streamlines.
Vector plots, turbulent energy contours, streamlines.
© ERCOFTAC 2004
 
References CFD5
=='''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.
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.
© ERCOFTAC 2004
 
Simulation Case CFD6
 
© ERCOFTAC 2004
=='''Simulation Case CFD6'''==
Solution strategy CFD6
 
==='''Solution strategy CFD6'''===


RANS modelling.
RANS modelling.
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Slant angle: 25°.
Slant angle: 25°.
© ERCOFTAC 2004
 
Computational Domain CFD6
==='''Computational Domain CFD6'''===


Domain: no details
Domain: no details
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y+ on solid surfaces : no details
y+ on solid surfaces : no details
© ERCOFTAC 2004
 
Boundary Conditions CFD6
==='''Boundary Conditions CFD6'''===


Solid boundaries:
Solid boundaries:
Line 307: Line 318:


Inlet, outlet and other boundaries: no details
Inlet, outlet and other boundaries: no details
© ERCOFTAC 2004
 
Application of Physical Models CFD6
==='''Application of Physical Models CFD6'''===


-        Realizable k-ε model with non-equilibrium wall functions
-        Realizable k-ε model with non-equilibrium wall functions


-        SST model
-        SST model
© ERCOFTAC 2004
 
Numerical Accuracy CFD6
==='''Numerical Accuracy CFD6'''===


No details
No details
© ERCOFTAC 2004
 
CFD Results CFD6
==='''CFD Results CFD6'''===


Cp, velocity profiles in the boundary layer over the slant part.
Cp, velocity profiles in the boundary layer over the slant part.
© ERCOFTAC 2004
 
References CFD6
=='''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.
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.
© ERCOFTAC 2004
 
Simulation Case CFD7
 
© ERCOFTAC 2004
=='''Simulation Case CFD7'''==
Solution strategy CFD7
 
==='''Solution strategy CFD7'''===


RANS modelling in unsteady mode.
RANS modelling in unsteady mode.
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Slant angle: 35°
Slant angle: 35°
© ERCOFTAC 2004
 
Computational Domain CFD7
==='''Computational Domain CFD7'''===


Full body (no symmetry condition used).
Full body (no symmetry condition used).
Line 353: Line 365:


-        10th workshop: 17 (coarse mesh) and 11 (fine mesh).
-        10th workshop: 17 (coarse mesh) and 11 (fine mesh).
© ERCOFTAC 2004
 
Boundary Conditions CFD7
==='''Boundary Conditions CFD7'''===


Inlet: turbulence intensity=2,5%
Inlet: turbulence intensity=2,5%
Line 363: Line 375:


Other boundaries: no details
Other boundaries: no details
© ERCOFTAC 2004
 
Application of Physical Models CFD7
==='''Application of Physical Models CFD7'''===


9th ERCOFTAC workshop:
9th ERCOFTAC workshop:
Line 387: Line 399:


-        SSG Reynolds stress model with modified ε equation (Hanjalic, Jakirlic) and standard wall functions
-        SSG Reynolds stress model with modified ε equation (Hanjalic, Jakirlic) and standard wall functions
© ERCOFTAC 2004
 
Numerical Accuracy CFD7
==='''Numerical Accuracy CFD7'''===


Convection scheme : 60% 2nd order central differencing, 40% 1st order upwind differencing.
Convection scheme : 60% 2nd order central differencing, 40% 1st order upwind differencing.
© ERCOFTAC 2004
 
CFD Results CFD7
==='''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).
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
© ERCOFTAC 2004
 
References CFD7
==''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.
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.
Line 403: Line 415:


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.
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.
© ERCOFTAC 2004
 
Simulation Case CFD8
 
© ERCOFTAC 2004
=='''Simulation Case CFD8'''==
Solution strategy CFD8
 
==='''Solution strategy CFD8'''===


RANS modelling.
RANS modelling.
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Slant angle: 25° and 35°.
Slant angle: 25° and 35°.
© ERCOFTAC 2004
 
Computational Domain CFD8
==='''Computational Domain CFD8'''===


Symmetry is used to compute half the domain. Stilts not included.
Symmetry is used to compute half the domain. Stilts not included.
Line 425: Line 438:


Approximate value of y+ on solid surfaces : between 55 and 550.
Approximate value of y+ on solid surfaces : between 55 and 550.
© ERCOFTAC 2004
 
Boundary Conditions CFD8
==='''Boundary Conditions CFD8'''===


Inlet:
Inlet:
Line 445: Line 458:


Other boundaries: symmetry
Other boundaries: symmetry
© ERCOFTAC 2004
 
Application of Physical Models CFD8
==='''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 SCL wall functions (see below)
Line 469: Line 482:


-        UMIST-N = UMIST Numerical
-        UMIST-N = UMIST Numerical
© ERCOFTAC 2004
 
Numerical Accuracy CFD8
==='''Numerical Accuracy CFD8'''===


Convection scheme : 3rd order Quick scheme (UMIST) or 1st order upwind scheme in case of numerical instability.
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.
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.
© ERCOFTAC 2004
 
CFD Results CFD8
==='''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).
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
© ERCOFTAC 2004
 
References CFD8
=='''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.
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.
© ERCOFTAC 2004
 
Simulation Case CFD9
 
© ERCOFTAC 2004
=='''Simulation Case CFD9'''==
Solution strategy CFD9
 
==='''Solution strategy CFD9'''===


LES.
LES.
Line 495: Line 509:


Slant angle: 25°.
Slant angle: 25°.
© ERCOFTAC 2004
 
Computational Domain CFD9
==='''Computational Domain CFD9'''===


Domain: [-2.2L;4.8L]x[-0.9L;0.9L]x[0;1.35L]. Ground plate and stilts included.
Domain: [-2.2L;4.8L]x[-0.9L;0.9L]x[0;1.35L]. Ground plate and stilts included.
Line 503: Line 517:


y+ on solid surfaces : no details
y+ on solid surfaces : no details
© ERCOFTAC 2004
 
Boundary Conditions CFD9
==='''Boundary Conditions CFD9'''===


Inlet: constant velocity
Inlet: constant velocity
Line 513: Line 527:


Other boundaries: slip walls
Other boundaries: slip walls
© ERCOFTAC 2004
 
Application of Physical Models CFD9
==='''Application of Physical Models CFD9'''===


Subgrid scale model: Smagorinky
Subgrid scale model: Smagorinky
© ERCOFTAC 2004
 
Numerical Accuracy CFD9
==='''Numerical Accuracy CFD9'''===


2nd order convection scheme and time marching (CFL number < 0.6)
2nd order convection scheme and time marching (CFL number < 0.6)
© ERCOFTAC 2004
 
CFD Results CFD9
==='''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).
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
© ERCOFTAC 2004
 
References CFD9
=='''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.
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.
© ERCOFTAC 2004
 
Simulation Case CFD10
 
© ERCOFTAC 2004
=='''Simulation Case CFD10'''==
Solution strategy CFD10
 
==='''Solution strategy CFD10'''===


RANS modelling.
RANS modelling.
Line 541: Line 556:


Slant angle: 25°.
Slant angle: 25°.
© ERCOFTAC 2004
 
Computational Domain CFD10
==='''Computational Domain CFD10'''===


Symmetry is used to compute half the domain. Ground plate included, no stilts.
Symmetry is used to compute half the domain. Ground plate included, no stilts.
Line 551: Line 566:


Approximate value of y+ on solid surfaces : 1
Approximate value of y+ on solid surfaces : 1
© ERCOFTAC 2004
 
Boundary Conditions CFD10
==='''Boundary Conditions CFD10'''===


Inflow: turbulence level 1%. nt/n = 1.
Inflow: turbulence level 1%. nt/n = 1.
Line 561: Line 576:


Other boundaries: no details
Other boundaries: no details
© ERCOFTAC 2004
 
Application of Physical Models CFD10
==='''Application of Physical Models CFD10'''===


Low-Reynolds number K-ε model (Yang-Shih).
Low-Reynolds number K-ε model (Yang-Shih).
© ERCOFTAC 2004
 
Numerical Accuracy CFD10
==='''Numerical Accuracy CFD10'''===


Mesh adaptation applied.
Mesh adaptation applied.


Convection scheme : 2nd order.
Convection scheme : 2nd order.
© ERCOFTAC 2004
 
CFD Results CFD10
==='''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).
Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).
© ERCOFTAC 2004
 
References CFD10
=='''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.
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.
© ERCOFTAC 2004
 
Simulation Case CFD11
 
© ERCOFTAC 2004
=='''Simulation Case CFD11'''==
Solution strategy CFD11
 
==='''Solution strategy CFD11'''===


RANS modelling.
RANS modelling.
Line 591: Line 607:


Slant angle: 25° and 35°.
Slant angle: 25° and 35°.
© ERCOFTAC 2004
 
Computational Domain CFD11
==='''Computational Domain CFD11'''===


Symmetry is used to compute half the domain. No stilts included.
Symmetry is used to compute half the domain. No stilts included.
Line 603: Line 619:


Approximate value of y+ on solid surfaces : 1
Approximate value of y+ on solid surfaces : 1
© ERCOFTAC 2004
 
Boundary Conditions CFD11
==='''Boundary Conditions CFD11'''===


Inlet: turbulence intensity=1%, nt/n=1.
Inlet: turbulence intensity=1%, nt/n=1.
Line 617: Line 633:


Other boundaries: opening boundary conditions.
Other boundaries: opening boundary conditions.
© ERCOFTAC 2004
 
Application of Physical Models CFD11
==='''Application of Physical Models CFD11'''===


-        Standard k-ε model with scalable wall functions
-        Standard k-ε model with scalable wall functions
Line 625: Line 641:


-        SSG Reynolds stress model with scalable wall functions
-        SSG Reynolds stress model with scalable wall functions
© ERCOFTAC 2004
 
Numerical Accuracy CFD11
==='''Numerical Accuracy CFD11'''===


Convection scheme: 2nd order.
Convection scheme: 2nd order.
Line 633: Line 649:


Mesh refinement, formulation of the boundary conditions (opening vs. slip walls), advection scheme.
Mesh refinement, formulation of the boundary conditions (opening vs. slip walls), advection scheme.
© ERCOFTAC 2004
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:
==='''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 [[Image:Image23.gif]]  [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]]  in some planes and profiles in the boundary layer above the slant part:


   
   
Line 642: Line 658:
   
   


k-epsilon model
'''k-epsilon model'''


25° slant angle:
25° slant angle:
Line 672: Line 688:
   
   


SST model
'''SST model'''


25° slant angle:
25° slant angle:
Line 699: Line 715:


Pressure coefficients on the rear of the body: Cp
Pressure coefficients on the rear of the body: Cp
© ERCOFTAC 2004
 
References CFD11
=='''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 (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.
Line 707: Line 723:


L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body, CFX Validation report (florian.menter@ansys.com)
L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body, CFX Validation report (florian.menter@ansys.com)
© ERCOFTAC 2004
 
 
Simulation Case CFD12
Simulation Case CFD12
© ERCOFTAC 2004
© ERCOFTAC 2004

Revision as of 09:45, 4 September 2008

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://labo.univ-poitiers.fr/informations-lea/Workshop-Ercoftac-2002/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 Image23.gif Image24.gif Image25.gif Image26.gif Image27.gif in some planes and profiles in the boundary layer above the slant part:



k-epsilon model

25° slant angle:

planes: y=0; y=100; y=180;

y=195; z=360

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=-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:

planes: y=0; y=100; y=180;

y=195; z=360

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 © ERCOFTAC 2004 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°. © ERCOFTAC 2004 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 © ERCOFTAC 2004 Boundary Conditions CFD12

Inlet: no details

Solid boundaries: no-slip walls

Symmetry plane: symmetry

Other boundaries: farfield Riemann-invariant conditions © ERCOFTAC 2004 Application of Physical Models CFD12

- SST model

- Explicit Algebraic Stress Model with ω-equation © ERCOFTAC 2004 Numerical Accuracy CFD12

Convection scheme : 1st order. © ERCOFTAC 2004 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:

planes: y=0; y=100; y=180;

y=195; z=360

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=-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:

planes: y=0; y=100; y=180;

y=195; z=360

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=-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


© ERCOFTAC 2004 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. © ERCOFTAC 2004 Simulation Case CFD13 © ERCOFTAC 2004 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°. © ERCOFTAC 2004 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 © ERCOFTAC 2004 Boundary Conditions CFD13

Inlet: no details

Solid boundaries: no-slip walls

Other boundaries: symmetry © ERCOFTAC 2004 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) © ERCOFTAC 2004 Numerical Accuracy CFD13

No details © ERCOFTAC 2004 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). © ERCOFTAC 2004 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. © ERCOFTAC 2004 Simulation Case CFD14 © ERCOFTAC 2004 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°. © ERCOFTAC 2004 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 © ERCOFTAC 2004 Boundary Conditions CFD14

Solid boundaries: no slip wall

Symmetry plane: symmetry

Other boundaries: no details © ERCOFTAC 2004 Application of Physical Models CFD14

SST model © ERCOFTAC 2004 Numerical Accuracy CFD14

No details © ERCOFTAC 2004 CFD Results CFD14

Velocity profiles in the boundary layer over the slant part, streamlines, turbulent energy contours. © ERCOFTAC 2004 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 © ERCOFTAC 2004 Simulation Case CFD15 © ERCOFTAC 2004 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°. © ERCOFTAC 2004 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 © ERCOFTAC 2004 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 © ERCOFTAC 2004 Application of Physical Models CFD15

Rescaled V2F model (Manceau, Carlson, Gatski) © ERCOFTAC 2004 Numerical Accuracy CFD15

No details. © ERCOFTAC 2004 CFD Results CFD15

Vector plots. © ERCOFTAC 2004 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


SPs (simulated parameters)






Detailed data


DOAP

CFD1


4.29


0, 10, 12, 20, 25, 30, 40, 50


pressure tomographies


Cd, streamlines, friction lines

CFD2


4.29


30


Effective viscosity


Cd, velociites

CFD 3



4.29


28


Pressure coef., Q-criterion contours


Cd, velocities, vorticity contours

CFD4


2.78


25, 35


Cp


Velocity profiles

CFD5


2.78


25, 35


Cp, turbulent energy contours


Velocity profiles, vector plots, streamlines

CFD6


2.78


25


Cp


Velocity profiles

CFD7


2.78


35


Cp


Velocity profiles, vector plots

CFD8


2.78


25, 35


Cp


Velocity profiles, vector plots

CFD9


2.78


25, 35


Cp


Velocity profiles, vector plots

CFD10


2.78


25


Cp


Velocity profiles, vector plots

CFD11


2.78


35


Cp


Cd, velocity profiles, vector plots

CFD12


2.78


25, 35


Cp


Velocity profiles, vector plots

CFD13


2.78


25


Cp


Velocity profiles, vector plots

CFD14


2.78


25, 35


Turbulent energy contours


Velocity profiles, streamlines

CFD15


2.78


25



Vector plots


Table CFD-A Summary description of all test cases © copyright ERCOFTAC 2004

Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers

Site Design and Implementation: Atkins and UniS

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