A three-dimensional model of particulate flows using the Reynolds Averaged Navier-Stokes method is presented. The governing equations of the gas-solids flow are supplemented with appropriate closure equations to take into account all the relevant forces exerted on the solid particles, such as particle-turbulence interactions, turbulence modulation, particle-particle interactions, particle-wall interactions, as well as gravitational, viscous drag, and lift forces. A finite volume numerical technique was implemented for the numerical solution of the problem. The method has been validated by comparing its results with the limited number of available experimental data for the velocity and turbulence intensity of the gas-particle flow. The results show that the presence of particles in the flow has a significant effect on all the flow variables. Most notably, the distribution of all the parameters becomes asymmetric, because of the gravitational effect on the particles and particle sedimentation. (C) 2011 American Institute of Chemical Engineers AIChE J, 57: 2977-2988, 2011