[PeterG]

Hi. New here. I have been working with CFD for about 5 months.

I have a compressible flow simulation that runs many thousands of iterations and appears to converge, but the air velocity at certain outlets is supersonic, finally "settling down" at 6-7 times as fast as the outlet velocity defined for those outlets. Early on in the solving it is at absurd velocities - like 50,000ft/sec, etc.

This cannot be right; there is nothing in the simulation's assigned physics that should make it go nearly this fast. Everything should be < Mach 1. When I increased the number of mesh elements at the problematic outlets, and ran the simulation again using the same relaxation factors, the simulation failed before getting anywhere close to convergence. As well, the outlet velocities are even more absurd, greater than 400,000 ft/sec, etc.

Is this common? Any simple things that tend to cause this sort of thing?

If relevant, I use Symscape's Caedium, but saw no forum for it so am posting my question here. I apologize in advance if it should be elsewhere.

Thanks in advance for any help whatsoever.

Peter Gobar