Non-reflective wall?
 

I've created a wave tank in CFX, but want to cut down on the amount of reflection from the back wall. The issue is that the water in the 'tank' rises when I induce the wall movement (expected) but that the undercurrent recircs off the back wall and heads back toward the body and need to make the readings as pure from the incoming wave as possible. I have the back wall pretty far back in an attempt to minimize this effect as long as possible, but the mesh it starting to get huge with all the extra space in there.

Is there a way to have a non-reflective boundary? Would making it a slip wall help? Maybe if I just make the mesh at the back wall coarse to cut down on the quality of the calcs back there (just thought of this this AM, so haven't tried it yet)?