Species Transport: How to determine the mass flux from concentration gradients?
 

Dear members,

I am modeling steady state diffusion using the species transport model for two species A & B. The geometry is a cube of air of 1 cubic centimeter with an orifice at the center of one face. The opposite face has been set as an inlet vent with defined mass fraction of species A (greater), and the lower surface of a bounded cavity beyond the orifice is set as an outlet vent to a lower mass fraction of species A (lesser).

After running the simulation, I have obtained a reasonably realistic concentration distribution of species A in the volume, i.e. I have the values of the concentration of species A at every point in the volume.

My problem is, how do I calculate the resultant rate of mass diffusion across the cavity in terms of [M][T]^(-3)?

Please help me.

Did you have any luck with this? I'm tackling more or less the same problem at the moment...

I had to switch to writing my own code, as Fluent couldn't offer multicomponent multiphase diffusion with ionic interactions.