Influence of particle rotation on the interaction between particle clusters and particle-induced turbulence

To investigate the collective behavior of solid particles in the particle-induced turbulence, a direct numerical simulation of homogeneous flow including a lot of settling particles was conducted. The flow around each particle was fully resolved by the finite-difference method. A particle was assumed to be rigid and spherical. The number of solid particles was up to 2048 and the number of grid for fluid flow was 268 millions. Particles moving with Reynolds number 300 formed clusters (high-concentration regions) due to wake-attractions. Influences of the loading ratio and particle rotation were particularly investigated. The rotation drastically affected numerical results. Irrotational particles were absorbed into clusters but rotational ones escaped. Such difference was caused by reverse direction of lift in the shear flows. Moreover, it was found that the particle-induced turbulence became severalfold of the total of disturbance by vortex shedding from each particle when particles formed clusters.