Thank you very much. I have another question. I want to simulate TGV at Re=1600, Ma=0.08. Can compressible N-S solver be used to simulate incompressible problems directly without ACM?

I moved this post here as it was a bit off topic.

You can, although as you approach the incompressible limit the simulation will become increasingly stiff. For the TGV, M=0.08 is standard and will work fine with compressible Navier–Stokes. However, using compressible for incompressible cases in general — like most things in CFD — is case dependent and dependent on what you are trying to investigate.

Thank you for your reply. I also see the Ma is set to be 0.1 in many articles, could I compare the results of Ma=0.08 with Ma=0.1?

I don’t know this for sure, but often when people state the Mach number for the TGV as 0.1, it’s actually ~0.081. But even if it where 0.1, the difference I think would be negligible. I actually looked at the effect of compressibility a little bit for the TGV in this paper: Effect of Flux Function Order and Working Precision in Spectral Element Methods | AIAA SciTech Forum

This wasn’t the main point of the paper, but I compare M=0.081 to M=0.3. The difference isn’t huge, and actually other things effect the result more that compressibility.