[cyln]

Hello,


I am simulating a steady 3D supersonic-diffuser flow with CFX. The supersonic diffuser has a test section upstream with M=4. Inlet BC is set to Ptot = 8.3 bars, Outlet is set to P_static = 1 bar. I expect to have a shock termination somewhere downstream of the diffuser throat.

k-omega SST turbulence model is used for turbulence closure.

When CFX starts to capture the shock system, there is flow separation downstream of the shock system and I am not sure whether it is real or not. the total pressure downstream of the shock system falls below 1 bar (about 0.5 bar). Since this is less that the outlet pressure, the solver places a wall at the outlet to avoid inflow from the outlet. This way, mass is not conserved and this leads to unstarting (The shock system moves upstream of the throat).

Is there anyone who has dealt with this problem? Which turbulence model is ideal for such a flow? Any other way to treat the outlet?

Cheers,
Cyln