EMMS mixture model with size distribution for two-fluid simulation of riser flows

Further development of an energy-minimization multiscale modeling approach to simulating two-phase flow under turbulent conditions that considers the size distribution of mesoscale structures, i.e. bubbles and clusters, is presented. User-defined values of minimum and maximum cluster or bubble diameters were specified. A uniform size distribution was first considered as a test case, in which the drag force comprised contributions from each size group. The mathematical form of the objective function describing the energy for suspension and transport was not altered. The heterogeneity index of this new drag modification was then used to simulate pilot-scale circulating fluidized-bed risers involving Geldart group A particles. The results were validated against available experimental data. The model is capable of capturing both axial and radial profiles of flow-field variables. (C) 2017 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.