In this work, we investigate the radial flow structure in gas-solids downer using Euler-Euler computational fluid dynamics (CFD) models. Solids are modeled as pseudo-fluid using kinetic theory of granular flow. In addition to the mass and momentum conservation equations, transport equation for fluctuating kinetic energy of the solids (modeled as granular temperature) is solved. The main focus of this work is the systematic investigation of the most suitable closures for the various force interactions in the system of interest. Results are presented for mean solids velocity, volume fraction, granular temperature and slip velocities for various closure forms. Sensitivity of the predicted results to the choice of closure forms is presented. Finally we emphasize the idea of matching slip velocities and the trends thereof with solids fraction as the key to developing a robust CFD model which has predictive capability over a wide variety of flow conditions. (c) 2008 Published by Elsevier Ltd.