3D flow separation on buildings
 

Hi everybody,
I've to evaluate if there is flow separation and eventual reattachment points on the roof of a building , which is sourronded by a huge parallelepiped of air (to simulate wind driven natural ventilation in buildings). How could I do?I've read about the plot of wall shear stress in 2D problem, but in my 3D case what is the better way?
Thanks a lot for any suggestion
Bests