Flow through two combined porous media with diffrent permeability
 

Hi,
I am trying to simulate flow through two porous media which are in series, I mean that first water goes to first porous media and then to second porous media which is just adjacent to first one. When I see the streamline of velocity it seems that water penetrates the first media but not go through the second one, besides it turns back from the interface between these two porous media and get out from the first one. Does this interface requires some special treatment? Geometry is 2D.
Thanks.