[CleverBoy]

Hello everybody,

I am trying to run a case with RANS-SST with farfield and symmetry BCs and freestream Mach number is 15.
When I got the results it always shows that flow starts with mach 15 and slows down in the freestream as in the attached contour picture.

What could be the reason for this?

[pcg]

If you are running a 2.5D case, aka a slice (symmetry BCs on "front" and "back"), the slide needs to be on the y-z plane instead of x-y. That is, at 0 AoA and 0 side-slip the farfield velocity is in the z direction (instead of x for 2D mode).

[CleverBoy]

Originally Posted by pcg

If you are running a 2.5D case, aka a slice (symmetry BCs on "front" and "back"), the slide needs to be on the y-z plane instead of x-y. That is, at 0 AoA and 0 side-slip the farfield velocity is in the z direction (instead of x for 2D mode).

Thank you for the reply. I am not using a 2.5D case. I thought that kind of cases can run with OpenFoam. My case is 2D.

Nevertheless, I run this same simulation with NEMO and there is no problem like this.

[CleverBoy]

Maybe this Mach contour will helpful. There are smaller Mach contour lines in the freestream. What could be the reason for this?

[pcg]

This is the reason https://github.com/su2code/SU2/issues/1851
You can lower the inlet turbulence intensity to more realistic values for external aero problems like this:
FREESTREAM_TURBULENCEINTENSITY= 5e-4
FREESTREAM_TURB2LAMVISCRATIO= 0.01

[CleverBoy]

Perfect. Thank you for the research and solution for it. I will try it first time when I have free time.