modelling of plate with momentum source

Bogesz

In CFX-5.5 I should model a 0.2 m thick perforated plate. It's function is to make pressure drop and rectify the flow in the Z direction, so the X and Y components of the velocity should be reduced close to zero. How should I define the momentum source to reduce the X,Y velocity components (by using a fluid subdomain with momentum source)? (the main flow direction is Z, but before the plate the fluid takes a U-turn, and I want no/little back flow after the turn that's why I need such a plate) Thanks Bogdan