free convective and diffusive mass transfer
 

I would like to know the exact boundary conditions for simulating free convective mass transfer over a vertical plate. i tried with pressure outlets on all the three sides (top, bottom and one of the sides) and the plate as a wall. Since it is a free convection mass transfer, I initialised the mass fractions with ambient values all over the domain and a constant mass fraction boundary condition was specified on the wall.The results gave qualitatively correct boundary layers for mass fractions but failed to give velocity boundary layer.

Also, is it possible to get the concentration gradient at the wall (of any shape viz., corrugated)inorder to check for the mass transfer coefficients.

Thanks in advance