[sosat1012]

Lets say we have a box where there is a source of gas CO2 (at the bottom) and it is shut by a membrane (top). The box with the membrane is in atmospheric environment (simplest case). I want to simulate in CFX the diffusion through the membrane and finally find out the mass fractions of the air and CO2 inside the box.

I create two domains: the bottle without the membrane and the membrane itself. The first one is a fluid domain defined to contain a mixture of air (constraint) and CO2 with the kinematic diffusivity of CO2 in air.

What i did was to define the membrane domain as fluid domain containing again the CO2 and Air(constraint) mixture but with different kinematic viscocity.

There is a common area (between box domain and membrane domain) though that i do not know whether to define as a boundary or as an interphase (i did it as an interphase and the solution has errors - i get no results)

Any help on this?

What type of domain should i define the membrane?

If solid then i can not find a way to insert the diffusion coefficient of the membrane interacting with the mixture