Particle shape effects on dynamic behaviors in a spouted bed: CFD-DEM study

Abstract

The Computational Fluid Dynamics-Discrete Element method (CFD-DEM) approach for cylindroid particles was developed to study the effects of particle shape on spouting behaviors in a flat-bottomed spouted bed. The gas motion was modelled with k-ε turbulent model, and the particles was represented with the realistic cylindroid shapes. The various particle contact scenarios and contact forces between cylinders, as well as the drag force model for non-spherical particles were comprehensively involved to describe the particle motions more accurately. With the aspect ratio of particle varying from L/d = 0.25 to 3.0, spouting behaviors including flow pattern, particle velocity, orientation and contact details were studied. Results found that cylindroid particles show the clear different orientations in the three regions of spouted bed. In spout, cylindroid particles tend to put their longer dimension parallel to the (vertical) flow direction, while in annulus the orientation tendency is contrary and particles tend to put their larger dimension perpendicular to their falling direction. The particle with L/d = 1.0 obtains the maximum projected area in spout and thus the largest drag force and the highest particle velocities. When L/d deviates from 1.0, with particle shape becoming flatter or longer, the particle projected area in spout accordingly decreases, resulting in the decreasing particle velocity and particle circulation rate. On the other hand, when aspect ratio deviates from 1.0, the obviously increasing particle contact number in annulus reflects their increasing interlocking effects and worse flowability.