Cluster formation and particle-induced instability in gas-solid flows predicted by the DSMC method

A numerical simulation is performed for a dispersed gas-solid flow in a vertical channel. Flow of the solid phase is obtained by calculating individual particle motions, i.e. by the Lagrangian method, while the gas flow is obtained by solving the equations of inviscid fluid. The Direct Simulation Monte Carlo (DSMC) method is used to take account of particle-to-particle collisions. Attention is paid to the case of low gas velocities and high solid loading, for which the solid phase strongly affects the gas flow field. Therefore the flow fields of gas and solid are determined simultaneously taking the interaction between both phases into consideration. It is found that the flow becomes unstable and inhomogeneous as the gas velocity decreases and the solid loading increases. Furthermore, effects of parameters such as the channel width and physical properties of particles on the instability and cluster formation are investigated.