Considering solid shear stress in MP-PIC simulation of a CFB riser

To enable successful multi-phase particle-in-cell (MP-PIC) simulations of circulating fluidized beds (CFBs), both the interphase drag force and interparticle collisions need to be carefully modeled. Particle collisions are usually represented by the solid stress consisting of the normal and shear components, in which the normal stress was found to have a leading role in the numerical stability of MP-PIC simulations, whereas the impact of the shear stress has seldom been reported. In this work, the effects of the solid shear stress are investigated by using two-dimensional simulations of the moderately dense laboratory-scale CFB riser with in-house MP-PIC code implemented on MFIX open-source platform. Cases including only normal solid stress and those considering both normal and shear solid stresses are simulated. The results of solids flux, axial and radial solids profiles are compared with available experimental data. The results show that the solid shear stress plays a minor role on the accuracy of simulation, and the increase of PPP (number particles per parcel) leads to a lower accuracy of simulation.