Hi, I am using colocated grid with the Rhie-Chow interpolation. It seems like when i am only modelling a total porous or total non porous flow, my code converges fine. However, once i model both a porous and non porous channel adjacent to each other, then i have problems with convergence, especially at very low level of permeability (<e-12). I am using an incompressible flow so i only use the Darcy law in the momentum eqn. Also, i only apply continuity of velocity and pressure at the porous/non porous interface. Anyone has any idea what is the problem? Thanks!

I would like to add that i am running an incompressible flow hence i only use Darcy's law in the momentum eqn. Also, i only apply continuity of velocity and pressure at the porous/non porous interface. Anybody has any idea what the problem is? Thanks!