Interior wall in free and porous media flow physics

I have filter model which i did cfd analysis in both laminar and free and porous media flow .

The red marked part (attached below) is rectangular plate which acts like a interior wall where the air-flow mixture after entering through the inlet hits the rectangular plate and diverts into different flow direction.

(Note :The air flow mixture doesn't go into the rectangular plate ,the plate is kept for diverting the flow into directions ).
In laminar physics i have given interior wall option but when coming to the free and porous media flow there is no interior wall option so i tried wall and gave slip but there is no use and also the whole plate is not selecting only the edge is been selecting don't know why ?
So what should i do know ?
please suggest me

Thanks in advance
Regards
The comsol model is attached below (sep10)
The picture which shows the plate is also attached below(1234.jpg)