Bi-layer coarse-grained DPM of gas–solid systems with mesoscale heterogeneity resolved

Abstract

Coarse-grained discrete particle models (CGDPMs) that treat a group of real particles as a coarse-grained particle (CGP) are potentially capable of simulating industrial-scale gas–solid systems. However, the use of large CGPs decreases the spatial resolution for fluid computation, such that the detailed hydrodynamics of mesoscale structures cannot be captured accurately. In this study, the CGPs were coupled with gas flow at fine scale through weight function to describe the mesoscale heterogeneity in fluid velocity, solid concentration and interphase forces, which accurately reproduced experimental results of fluidization, in terms of bed expansion, bubble behaviors and voidage distribution. However, this extension incurred high computational cost due to large amounts of fluid cells. To speed up the computation, the gas flow was relaxed under frozen CGP configurations to evaluate the interphase forces on-the-fly. A bi-layer CGDPM thus proposed was demonstrated to be nearly 20 times faster than original fine-grid CGDPM for comparable accuracy.