CFD Online Discussion Forums - How to add water in multiphase FSI coupling?

Hi all,
I'm doing multiphase FSI coupling using OpenFOAM (fluid) and our in-house solver (solid). The case I want to simulate includes a porous media baffle, with water on the left side and no water on the right. I want to simulate the process that water on the left flows into the porous media and then flows into the right side.
At present, I've got the displacement and the seepage velocity (calculated in our in-house solver) on the interface and passed to the boundary in OpenFOAM. How could I add the additional water due to the seepage velocity on the interface?

I've tested a volumetric flow BC 'flowRateInletVelocity' and found it defines the velocity on the boundary according to the volumetric rate you set. It is exactly the opposed to what I want to achieve. It seems that what I want is similar to the wave generation BC. Is there anyone who can share some experience with me?

Thanks in advance!