To establish this model, the
following assumptions are proposed: (i) the flow profile is
assumed to be constant along the depth axis (depth-to-width ratio
greater than 10); (ii) the variations of the concentration do not
modify the viscosity and the density of the fluid (diluted solutions
and no free convection); (iii) the channel walls are assumed to
be smooth (roughness and experimental imperfections are neglected);
and (iv) the wall surface tension forces are neglected,
and the medium is assumed continuous.