When I create a slice plane and use the calculator (or perl) to determine the massflow at this plane I get zero. The geometry is simple (a wedge of a tube, with hexahedra and wedges at r=0). At the outlet I get the expected value. Does somebody else know this problem ?

It works fine for me. I'd check that the calculator is firstly picking up the correct plane, and that secondly the plane is perpendicular to the flow and not going through the inlet and outlet ? Sorry I can't be much more help than that, but I've not experienced any problems with this. Bob