Hi !

I am currently using Fluent (and Gridgen) to try to capture the wingtip vortices properly. I was wondering if you have any tips, references, or even websites concerning this study and particularly the choice of the turbulence model (am using Spalart but wish to try RSM, unfortunately this one does not want to converge).

A study made some time ago (I don't quite remember where I read this), revealed that increddibly, between S-A, Rke, SST-kw and RSM, for this problem you should always choose S-A or RSM. Rke and SST-kw were found to give much poorer results than the other 2. S-A was quite very close to RSM and both to experimental results.

Of course that S-A is much easier to converge, also because when your tip vortex will be shedding, RSM will very improbably be able to obtain a stationary solution and you will be forced to do a transient calculation. This is maybe the most common reason for difficult convergence with RSM (but people generally do not understand that RSM is sometimes too much physics for a stationary solution).

And another "tip": do not make a very dense mesh but rather adapt it by the gradient of pressure (you'll have to play a little with the limits) to capture the vortex path and the results will be more than satisfactory.

Best whishes, Razvan

There's a AIAA paper authored by the folks at Fluent Inc. Kim and Shin on the very same problem you described. Google it!