Inlet boundary condition for gas dispersion in low Re channel flow
 

Hi everybody,

I'm currently examining the dispersion behavior of ammonia in air.
The air moves with 0.5 m/s in x-direction, but the ammonia dispersion proceeds much faster.
Do you have any idea how to set up the boundary condition at the inlet in a physically reasonable way? When I set the concentrations of O2, N2 and ammonia to zero gradient, i think I at some point in time I will add ammonia to my control volume instead of washing it away with clean air. When I set the concentrations to 23% O2+77% N2+zero Ammonia, I always get a high concentration difference which speeds up the dispersion in negative x-direction.
Do you have any better ideas?

Best regards,

Robert