For now i just use the default resistance coefficients for the porous zone (211100000 m^-2).I dont get exactly what you mean by diffusivity. I am pretty new to CFD Simulation, sorry for the basic question. I googled it and dont get it for 100%. Do I have to add a User-Defined Scalar for the transport of the fluid with the porous domain?
Again, thank you very much for your Input!