Dense gas-solid flows show significantly higher stresses compared with dilute flows, mainly attributable to particle-particle friction in dense particle flows. Several models developed have considered particle-particl...Dense gas-solid flows show significantly higher stresses compared with dilute flows, mainly attributable to particle-particle friction in dense particle flows. Several models developed have considered particle-particle friction; however, they generally underestimate its effect in dense regions of the gas-solid system, leading to unrealistic predictions in their flow patterns. Recently, several attempts have been made to formulate such flows and the impact of particle-particle friction on predicting flow patterns based on modified frictional viscosity models by including effects of bulk density changes on frictional pressure of the solid phase. The solid-wall boundary is also expected to have considerable effect on friction because particulate phases generally slip over the solid surface that directly affects particle-particle frictional forces. Polydispersity of the solid phase also leads to higher friction between particles as more particles have sustained contact in polydispersed systems. Their effects were investi- gated by performing CFD simulations of particle settlement to calculate the slope angle of resting material of non-cohesive particles as they settle on a solid surface. This slope angle is directly affected by frictional forces and may be a reasonably good measure of frictional forces between particles. The calculated slope angle, as a measure of frictional forces inside the system are compared with experimental values of this slope angle as well as simulation results from the literature.展开更多
文摘Dense gas-solid flows show significantly higher stresses compared with dilute flows, mainly attributable to particle-particle friction in dense particle flows. Several models developed have considered particle-particle friction; however, they generally underestimate its effect in dense regions of the gas-solid system, leading to unrealistic predictions in their flow patterns. Recently, several attempts have been made to formulate such flows and the impact of particle-particle friction on predicting flow patterns based on modified frictional viscosity models by including effects of bulk density changes on frictional pressure of the solid phase. The solid-wall boundary is also expected to have considerable effect on friction because particulate phases generally slip over the solid surface that directly affects particle-particle frictional forces. Polydispersity of the solid phase also leads to higher friction between particles as more particles have sustained contact in polydispersed systems. Their effects were investi- gated by performing CFD simulations of particle settlement to calculate the slope angle of resting material of non-cohesive particles as they settle on a solid surface. This slope angle is directly affected by frictional forces and may be a reasonably good measure of frictional forces between particles. The calculated slope angle, as a measure of frictional forces inside the system are compared with experimental values of this slope angle as well as simulation results from the literature.
