In this paper, principles of computational fluid dynamics (CFD) are used to study ultrafiltration (UF) process. Model has been developed by a new technique in which permeation of solvent molecules is introduced to system via appropriate sink terms in conservation equations for computational domain. Experimental data and fittings are applied in model development. Model results have been compared for two and three-dimensional geometries. Finally a time step and mesh size independent model has been developed in two dimensions for modeling the permeation flux vs. filtration time in a gelatin-water UP system. Final model is able to predict steady-state permeation flux with relative error less than 2%. Accuracy of calculation is investigated through the comparison between mass imbalance and sum of local fluxes. Modeling results show that increase in cross flow velocity (CFV) and trans-membrane pressure (TMP) leads to increase in permeation flux but decrease in solute concentration and rejection of solute particles from membrane surface makes permeation flux increase. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.