[Transonic]

Hello, I’ve been researching the best outer domain shape for simulating an aerofoil in M=0.8 flow but haven’t found a good resource that explains this please?

These are the options that I’ve come across:
C-grid
Circle
Elliptical

Is there maybe a rule for when to choose a certain outer grid shape? Also, how does the outer grid affect the simulation please?

[siw]

It does not matter and there is no 'best'. Just make sure the fluid domain boundaries are far enough away from the aerofoil so they do not affect the results.

If you are unsure make a mesh (same resolution, y+ etc.) with different boundary shapes and see how the results differ - hopefully they will be the same (or similar enough that you are content). Focus more on ensuring there a no rapid element volume changes, high skewness etc.