the wall-modeled les simulation for windsor model
TRANSCRIPT
The Wall-modeled LES simulation for Windsor model
Shijun Chu, Chao Xia, Zhigang Yang
SHANGHAI AUTOMOTIVE WIND TUNNEL CENTER
TONGJI UNIVERSITYPage 1
CONTENT目 录
1 Introduction
2 Result & Discussion
3 Conclusion
Page 2
1、Introduction
Ugo Piomelli et al., Annu. Rev. Fluid Mech., 2002
Wall–stress model
Hybrid RANS-LES
T. Mukha et al., Comput. Phys. Commun,2019
Splading law
ODE-based
Modified by IDDES
WM-splading
WM-ODE
WMIDDES
Background
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1、Introduction
What did we do?
Software OpenFOAM V2012
DES-type WMLES-type
Turbulence model SST-DDES (WMER)；SST-IDDES (WMER&WRER)
WM-splading (WMER);
WM-ODE (WMER);
WMIDDES (WRER);
Numerical scheme DES hybrid (linear upwind + linear) LUST
Time step 5*10e-5 5*10e-5
pimple 10 per time step 10 per time step
A.P. Gaylarda et al., J. Wind Eng. Ind. Aerodyn.,2017 Page 4
2、Result && Discussion
Force coefficient
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2、Result && Discussion
Cs coefficient
Base pressure
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2、Result && Discussion
Pressure coefficient in cutting line of y=0 plane
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2、Result && Discussion
Instantaneous Q isosurface (Q=1000)
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2、Result && Discussion
PSD of drag coefficient
The resolved frequency: DES-type < WMIDDES < WMODE&WM-splading
WM-ODE
WM-splading
WMIDDES
DES types
Numerical fluctuation
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2、Result && Discussion
Streamlines on the plane of y=0
Urms on the plane of y=0
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2、Result && Discussion
Streamlines on the plane of z=0.194
Urms on the plane of z=0.194
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2、Result && Discussion
Streamlines on the plane of x=0.630
Urms on the plane of x=0.630
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2、Result && Discussion
Discussion
Wall–stress model
WMIDDES
wall model is only adopted in first cell
near the wall.
It is safer because the RANS regions are determined by the mesh resolution of the wall.
Shur et al., Int. J. Heat Fluid Flow., 2008
External region is all simulated by LES
If mesh resolution cannot satisfy the requirement of LES, the stress depletion will occur.
WMLES
DES type
DDES
IDDES
Almost all the boundary layer run in the mode of RANS
Safe but there will be the gray area effect.
Switch the mode (DDES or WMLES) according to the state of flow.
Safe and fewer gray area.
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3、Conclusions
Due to the bi-stable phenomenon existing in the wake of the Windsor
model, it is hard to evaluate the performance of different turbulence
model.
DDES is a pretty safe turbulence model but will suffer from serious
gray area effect. The IDDES method can perform better with the wall
resolved mesh.
The wall modeled LES can capture more TKE, but it may have
problem in predicting frictional drag. WMIDDES is potential way to
avoid run the LES in the coarse mesh region.
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