vikash kumar

Dear CFD expert,

                                        Greetings! I am working on the interdigitated flow channel, where mating surfaces (internal)  are supposed to diffuse the liquids from one side to the other. I experimented with different boundary conditions: internal as internal, which led to merging the surfaces and making a single entity. Additionally, I made internal as wall, which prevented the liquids to cross and do diffusion is observed . I am intended to observe diffusion at mating surfaces. Could you please suggest a suitable boundary condition?

Well, After consulting the experts , I have been suggested to write UDFs with species mass flow through the porous wall.Can any one suggest on how to proceed with writing UDFs?