2nd automotive cfd prediction

2nd Automotive CFD Prediction

WorkshopMarian Zastawny, Peter Altmann, Sylvain Lardeau

Siemens Digital Industries Software

Simcenter STAR-CCM+

Tessellated Surface

Wrapped Surface

Remeshed Surface

0 448 896 1,344 1,792

Complex Geometry Handling

Speed and Performance

Accurate Physics

Robust and Precise Meshing

Workflow Automation

Intelligent Design Exploration

Turbulence Modelling

Statistical model (RANS)

1. Standard

2. High-Re

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

12. Standard

13. SST

14. Linear pressure-strain

15. Quad. Pressure-strain

16. EB-RSM

Scale-Resolving

17. SA

18. SST k-w

19. EB k-e

20. Smagorinsky

21. WALE

22. Dynamic Smagorignsky

Influence of modelling assumptions

Influence of user input

Robustness

Why to use SRS in automotive?

Windsor Body RANS

Analysed results

Wall-Modelled RANS

SST, a1 = 1.0 Lag EB

Wall-Resolved RANS

SST, a1 = 1.0 Lag EB

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

Windsor Body SRS

Wall-Modelled DDES

Wall-Resolved DDES

DDES Summary

• Mean flow solution is achieved almost

instantaneously

• Wake prediction is visibly better than in

• Wall-Modelled mesh simulation appears to

agree more with the experiment

• Agreement in wake prediction is correlated

with the agreement in reported forces

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

Unrestricted | © Siemens 2021 | Version 2021.2 | Siemens Digital Industries Software | Where today meets tomorrow.Page 15

Wall-Modelled SRH

Wall-Resolved SRH

DDES vs SRH

• 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

DrivAer

Summary

Forces Comparison

RANS Scale-Resolved

Open questions

• Impact of time-step

• Impact of numerical discretization

• Impact of the tunnel walls on CL and CM

• Sensitivity to Boundary Conditions

ContactMarian Zastawny

Senior Application Engineer200 Shepherds Bush Road

W6 7NL London

United Kingdom

E-mail marian.zastawny@siemens.com

2nd automotive cfd prediction

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