[asutoshpadhy]

I have a cuboid that has three zones, top, middle and bottom. The top zone has a particle inlet, an air outlet and a particle outlet, while the bottom zone has an air inlet. I intend to pass the air through the middle zone into the top one without the discrete particles passing through to below it, like a semi permeable membrane.*Air goes up, but particles can't flow down.

The middle zone is thin and I have changed it from interior to porous jump, given it a reflect BC for DPM and a high permeability coefficient. But no matter how much I change the BCs the particles somehow seem to pass through the sides of the cuboid, as shown in the particle tracks. I need help modeling the 'particle lock', please suggest a way to do so.