Mass diffusion in a binary mixture of viscous fluids confined between a rotating disk and a porous medium of finite thickness

The diffusion effect in a binary mixture of incompressible viscous fluids confined between a rotating disk and a porous medium of finite thickness has been discussed. It is assumed that the lighter component is present in a small quantity. It is found that the pressure gradient created by the rotation of the disk in the free flow region separates the two components in the binary mixture in such a way that the concentration ratio of the lighter component decreases in both the regions. The concentration ratio of the lighter component in the porous medium is the maximum at the interface and then decreases sharply to zero indicating the boundary layer formation at the interface. This separative effect increases with the increase of the Darcy number, i.e., with the decrease of the permeability of the porous medium. These results are applicable for dispersion of fertilizers or other chemicals in an agricultural field.