A study on periodic boundary condition in direct numerical simulation for gas-solid flow

Direct numerical simulation (DNS) of gas-solid flow at high resolution has been carried out by coupling the lattice Boltzmann method (LBM) for gas flow and the discrete element method (DEM) for solid particles. However, the body force periodic boundary condition (FPBC) commonly used to cut down the huge computational cost of such simulation has faced accuracy concerns. In this study, a novel two-region periodic boundary condition (TPBC) is presented to remedy this problem, with the flow driven in the region with body force and freely evolving in the other region. With simulation cases for simple circulating fluidized bed risers, the validity and advantages of TPBC are demonstrated with more reasonable heterogeneity of the particle distribution as compared to the corresponding case with FPBC. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.