CFD simulation of hydrodynamics in the entrance region of a downer

Abstract

A gas turbulence–solid turbulence model ( k– ε– Θ– k p ) was used to simulate the hydrodynamics in the entrance region of a downer. This model incorporates a k– ε turbulence model for gas phase, a k p turbulence model and a kinetic theory description of solid stresses characterized by granular temperature ( Θ) for solid phase. The predicted profiles of local solids fraction and particle velocity have good agreement with the experimental data in a wide range of solids fraction. The solid pressure has a large gradient in the inlet region, which becomes a main driving force for the particles to move from the center to the wall. The sensitivity analysis shows that the inlet granular temperature has a large influence on the predicted results. Over the whole flow field, a clear relationship between the diffusion coefficient of particles and the local solids fraction is found, that is, a smaller solids fraction corresponds to a larger diffusion coefficient.