Download - 2nd Automotive CFD Prediction
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2nd Automotive CFD Prediction
WorkshopMarian Zastawny, Peter Altmann, Sylvain Lardeau
Siemens Digital Industries Software
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Simcenter STAR-CCM+
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Tessellated Surface
Wrapped Surface
Remeshed Surface
0%
25%
50%
75%
100%
0
448
896
1,344
1,792
0 448 896 1,344 1,792
SC
ALIN
G
SP
EE
D U
P
CORES
Complex Geometry Handling
Speed and Performance
Accurate Physics
Robust and Precise Meshing
Workflow Automation
Intelligent Design Exploration
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Turbulence Modelling
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Statistical model (RANS)
SA
1. Standard
2. High-Re
k-e
3. Std.
4. Std. 2-layer
5. Std. low-Re
6. Realizable
7. Real. 2-layer
8. AKN
9. V2-f
10. EB k-e
11. Lag EB k-e
k-w
12. Standard
13. SST
RSM
14. Linear pressure-strain
15. Quad. Pressure-strain
16. EB-RSM
Scale-Resolving
DES
17. SA
18. SST k-w
19. EB k-e
LES
20. Smagorinsky
21. WALE
22. Dynamic Smagorignsky
Cost
Influence of modelling assumptions
Influence of user input
Robustness
Model
High
Low
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Why to use SRS in automotive?
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Windsor Body RANS
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Analysed results
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Wall-Modelled RANS
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SST, a1 = 1.0 Lag EB
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Wall-Resolved RANS
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SST, a1 = 1.0 Lag EB
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RANS Comparison
• Wall-Modelled RANS appears to be closer to
experiment than Wall-Resolved RANS
• SST (a1=1) predicts higher drag coeffcients
• Wake prediction is somewhat correlated with the
reported forces
• Change in velocity profiles is less substantial than
change in drag coefficient
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Windsor Body SRS
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Wall-Modelled DDES
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Wall-Resolved DDES
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DDES Summary
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• Mean flow solution is achieved almost
instantaneously
• Wake prediction is visibly better than in
RANS
• Wall-Modelled mesh simulation appears to
agree more with the experiment
• Agreement in wake prediction is correlated
with the agreement in reported forces
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Scale-Resolving Hybrid (SRH) Turbulence Model
Model Description
When to Use it?
Typical Applications
• Increased fidelity unsteady RANS type modeling
• Higher accuracy than comparable URANS models
• Enhanced temporal modeling for increased realism
• Enables potential accuracy improvement to existing URANS
simulations
• Minimal additional computational cost
• Minimal work for setting up
• Mid-fidelity unsteady applications
• Applications where URANS previously was used
Increased fidelity URANS
URANS
SRH
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Wall-Modelled SRH
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Wall-Resolved SRH
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DDES vs SRH
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• Impact of changing the mesh is the same for
SRH as for DDES
• SRH profiles are generally in better
agreement with experiment than DDES
• SRH shows less sensitivity with respect to
the numerical set-up
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DrivAer
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Summary
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Forces Comparison
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RANS Scale-Resolved
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Open questions
• Impact of time-step
• Impact of numerical discretization
• Impact of the tunnel walls on CL and CM
• Sensitivity to Boundary Conditions
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ContactMarian Zastawny
Senior Application Engineer200 Shepherds Bush Road
W6 7NL London
United Kingdom
E-mail [email protected]
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