The influence of concentration polarization on the permeate flux in the ultrafiltration of aqueous Dextran T70 solutions can be described by (i) the osmotic pressure model and (ii) the boundary layer resistance model. In the latter model the hydrodynamic resistance of the non-gelled boundary layer is computed using permeability data of the Dextran molecules obtained by sedimentation experiments. It is shown both in theory and experiment that the two models are equivalent.
Wijmans, J. G., Nakao, S., van den Berg, J. W. A., Troelstra, F. R., & Smolders, C. A. (1985). Hydrodynamic resistance of concentration polarization boundary layers in ultrafiltration. Journal of membrane science, 22(1), 117-135. https://doi.org/10.1016/S0376-7388(00)80534-7