How to see lauch of swirls inside a turbulent flow

Greg

Hello everybody,

I would like to compute the torque on a flap but there are strong oscillations in the total moment reported by Fluent. I guess that there are some unsteady phenomenas convected, such as lauch of swirls around the flap that could probably explain these oscillations but i need to proove it by a transcient calculation. The problem is that it seems difficult to have and idea of a time and spatial scale of swirls to refine the grid around the flap and to define an appropriate time step. I use a K-w SST Rans model and i first try to see these unsteady phenomenas with a 2D simulation.

So my question is : how to define an appropriate time step and a correct spatial discretization in order to see swirls lauch around the flap ?

Thanks a lot for your explanations and advices, Regards Greg