Vortex shedding in polyflow

YALIN KAPTAN

Hi,

I am using Polyflow for the drag reduction with polymers and my geometry is flow past a cylinder which is a well known bechmark problem. In this problem after Re = 40 value (the flow is laminar here) there should appear vortex shedding but Polyflow always gives symmetric results for the velocity distribution (for example at Re=200). Can anybody help about why polyflow gives symmetric streamfunction or velocity contours or how can we obtain vortex shedding.

Note: We tried some differantial models, generalized viscoelastic models, steady and unsteady solutions. They are always symmetric.