Discrete element modeling for flows of granular materials

Abstract

Pneumatic transports of solid particles in vertical, horizontal and inclined pipes were studied numerically using the Discrete Element Method (DEM) coupled with Computational Fluid Dynamics (CFD). Various flow regimes observed in experiments conducted using different gas velocities and solid concentrations were reproduced computationally. Pneumatic transport in the presence of an electrostatic field was studied using CFD-DEM simulations coupled with a simple electrostatic field model. At sufficiently high field strengths, reversed flow of solids may be observed. Bulk granular attrition occurring in various systems was modeled with a diffusion type equation. The model reproduced much of the experimentally observed behavior and numerical simulation results. Finally, voidage wave instability in a liquid fluidized bed was investigated experimentally using Particle Image Velocimetry and numerically using CFD-DEM simulations. Voidage waves consisting of alternating regions of high and low solid concentrations were observed to form and travel in a coherent manner along the fluidized bed.