My goal is to numerically solve the convection-diffusion equation of the form:$$\frac{\partial C}{\partial t} = \nabla (D \nabla C) - \nabla (v C)$$$C$ is concentration and $D$ is the diffusivity constant.I am simulating this on a small flat plate model of porous media.I am assuming that fluid flow goes across the plates through the porous media from right to left and gas flow occurs from top to bottom inside the porous media and mass transport occurs between the gas and the fluid. I am modeling this in a commercial solver.I assigned a mass flow to the fluid inlet and a constant pressure to the fluid outlet to model the fluid flow. I keep having trouble modeling the gas flow. I tried setting a gradient by assigning a constant pressure at the inlet and outlet of the porous media but that does not seem correct. I'm beginning to think that there is a more fundamental problem with my approach. My question: is it correct to assign a gas pressure or a mass flux at the inlet and outlet to the porous domain? Would a mass flux be required at the interfaces to the fluid regions as well? Is there a specific approach for modeling gas flux?
Mass transport in porous media
pde;fluid dynamics;boundary conditions