Vector field of space averaged speed
 

Hi! I'd like to plot a 2d (xy) vector field of the mean velocity of a 3d flow averaged in the z direction. I know how to compute the mean velocity vector components on one particular line (using the surface integral utility) but I can't manage to obtain the vector field plot y the whole xy plane. I imagine I have to define a UDF which computes the integral of the flow in each line (x = constant, y = constant, z = variable) pasing through each cell of a domain, but I can't figure out how to do this. For this I would need a macro which gives me the cell that contains a specific point, or something similar, but I can't find anything like this. Does anyone have any idea of how to do this? Thanks