[UDS_rambler]

hi everybody,
I'm a biomedical engineering student developing a project for an exam. I'd like to describe the diffusion of oxygen through a porous membrane. In particular I'd like to evaluate the transient of this diffusion. I decided to use a porous jump to consider the porous media. the model is really simple: two different chambers one with only oxygen and the other one with only water (I want to fill this chamber with oxygen untill diffusion saturates!) No convection is present, the aim of this work is evaluate only diffusion.
My problem is that I can't understand how darcy's law is used by FLUENT to solve the transport of oxygen through the membrane. Shouldn't it used only for laminar flows through a porous media?? In this context I don't know what value of permeability is suitable for this simulation as soon as the permeability constants that I have are in m^2/s (like diffusivity in Fick's law) and the simulation requires a permeability constant in units of area e.g. m^2.
could you help me understand this?
thanks in advance!