set UDS value at interior BC

Simon

Hi, I'm trying to solve a UDS (2D)in a porous zone confined by walls on 3 corners and an interior interface with a fluid zone on the remaining corner. The UDS needs to be solved only in the porous domain and not in the fluid zone, where it has been deactivated. Only diffusive flux is active and convective flux function is equal to zero. The boundary conditions that need to be set are (being phi the uds):

1.grad(phi) = 0 on the walls; (easily done by GUI) 2.phi = 0 on the interface; source terms are present throughout the whole porous region;

I have tried to find out how FLUENT deals with interiors and what BC does it set for a UDS. Having not found an answer, my guess is that by default it sets grad(phi) = 0, so my question is: how can I set the BC no 2.? I' have tried patching with DEFINE_ADJUST cells next to the interior with C_UDSI(c,t,0)=0 but uds conservation is not respected. Please help! Any tip or suggestion is very welcomed!

many regards, Simon