In the present contribution an eddy-resolving scheme (large-eddy simulation) is combined with an efficient particle tracking algorithm for individual particles and a deterministic collision model. The purpose is to set-up a reliable methodology for the prediction of complex particle-laden two-phase flows at high mass loadings. The objectives are two-fold. On the one hand the suitability of the entire method to tackle practically relevant turbulent flows should be proven. On the other hand the influence of the fluid-particle interaction (two-way coupling) as well as particle-particle collisions (four-way coupling) is investigated in detail. For both purposes this numerical study is aligned to the experimental investigation of the bluff-body configuration by Boree et al. [J. Boree, T. Ishima, I. Flour, The effect of mass loading and inter-particle collisions on the development of the polydisperse two-phase flow downstream of a confined bluff body, J. Fluid Mech. 443 (2001) 129-165]. In this set-up a fully developed pipe flow laden with polydisperse glass beads enters a cylindrical chamber with an outer annular confined flow without swirl. In contrast to previous numerical studies both mass loadings (eta = 22% and 110%) and thus also inter-particle collisions are taken into account. Contrary to the experimental investigation the predictions allow to artificially isolate different physical effects in order to clarify their importance. Especially for the high mass loading case interesting new results about the role of fluid-particle interactions and particle-particle collisions are enlightened. (C) 2012 Elsevier Ltd. All rights reserved.