The effect that you mentionned is probably accentuate with a 3D mesh also. Obvisouly, my strategy is to create IC with a steady-state turbulence model with an appropriate mesh and going forward in unsteady state afterward. But in this case, like you mentioned, what could be my approach then? Going straight with a unsteady case can take a long time before I can validate the mesh, the drag coefficient and all of the other parameters.....