A simple averaged equation model for two-phase flows is used to perform high-resolution three-dimensional numerical simulations of aas-solid flow in a fluidized bed. Results are compared to experimental observations of Van den Moortel et al. [Chem. Eng. Sci. 53 (10) (1998) 1883]. It is found that a simple averaged equation model, which accounts directly for only simple fluid-particle interactions, captures the basic physics of the two-phase flow provided sufficient resolution is used. This is because mesoscale structures produced by the nonlinear interactions represented by the nonlinear terms in the averaged equations have dominant effects on the macroscale. Similarities and differences between our results and those of Agrawal et al. [J. Fluid Mech. (2000) submitted for publication] and the implications for future directions in two-phase flow theory for fluidized beds are discussed. Published by Elsevier Science B.V.