Vortex in an intake pipe, critical submergence
 

Dear users,

I try to simulate and visualize a vortex phenomenon just over a vertical intake pipe in a symetric waterway (uniform velocity and geometric conditions known to get an air-core vortex). My first conclusion is that if I don't influence the flow to get vorticity, I can't visualize any vortex over the pipe (output with a constant volume flow-rate). When I put a component fencing only one side of the flow, it creates a large eddy which then comes over the pipe and triggers the vortex phenomenon.

So my question is: how to be sure to detect the vortex in the symetric cases and if it is impossible, what disruption can be sufficient to trigger the vortex phenomenon?

To detail my case: in my prepin I set up the third order for the momentum advection and a RNG turbulence model.

Thanks!

All you have to do is add an asymmetry in the initial or boundary conditions like a small cross flow. However, keep in mind that the intensity of the vortex at the intake at steady-state depends to the total vorticity in the initial or boundary conditions because of the conservation of the total angular momentum (this is why a symmetric flow does not create the vortex). So by introducing an asymmetric flow you will influence the final solution.