[ZachFrankman]

I am using FLUENT to make a 2D model of a a 50um x 1.5cm microfluidic channel, and I want to use the Species Mixing model with wall reaction to model living cells on the bottom consuming O2 and producing N2. I use a site-specific molecule silicon as a surface-bound catalyst to model the cells.



The flow in this channel is very low: 2.5nL/s, giving a maximum flow velocity of around 7.5e-5m/s.

The diffusion coefficient for oxygen in water is 3e-9m2/s, which makes diffusion significantly faster than the convection.


When I set up this model, I find that the O2 flowing in from the inlet rapidly diffuses out of the chamber through the reaction wall, as does the N2 produced by the reaction. I would like for the O2 to slowly be depleted as it reacts with the surface-bound catalyst, slowly filling the chamber with N2.



Is there any way to write a UDF that specifies no O2 or N2 species diffusion through the walls? Is there a way to specify zero diffusive flux through a reaction wall?