Accurate modelling of the flow and concentration polarisation in pressure driven membrane processes is inhibited by the complex couplings in the flow equations along with any added effects of variable solution properties. A generic computational fluid dynamics (CFD) model has been developed which incorporates these effects and describes the flow across the membrane wall. The results have been validated against classical solutions available in the literature. Extended work indicates that overly simplified expressions for the dependence of viscosity and diffusivity on concentration produce velocity and concentration profiles that may grossly misrepresent reality.