Free surface vortex flow

Guillaume

Hi my name is Guillaume

I am using CFX 5.7.1 to model a gas entraining vortex above an intake pipe. So the phenomenon is free surface and presents a high swirling pattern. The geometry is a tank with a tangential injection.

When I simulate a high injection flow rate (therefore high circulation), I obtain the vortex. But when I use a small flow rate, I don't obtain any vortex, whereas the experiment shows a very strong gas entraining vortex.

I tried lots of things: mesh resolution, timestep, underelaxation, turbulence model (k-e, SSG), inhomogeneous/homogeneous. The free surface stays perfectly flat.

Any ideas? Any similar problems already experienced?

Cheers Guillaume