On the effect of static and dynamic particle size distribution on flow turbulence modulation

The effect of an evolving particle size distribution due to particle agglomeration and breakup, and the direction and absence of gravitational acceleration, on flow turbulence modulation is investigated using large eddy and discrete particle simulation of a turbulent channel flow. The results are compared with the case in which the particle size distribution is static and where only inter-particle collision is allowed. Due to the small particle Stokes number considered, inherent in a solid-liquid flow, and the small simulation time, only small effects were observed for the static versus dynamic particle size distribution on the fluid turbulence. For vertical channel flows, however, the influence of flow direction and gravity lead to different particle segregation patterns which, together with changes in wall shear stresses and mass flow rate due to buoyancy effects, do affect the flow turbulence and the evolution of inter-particle collisions, collision efficiency and agglomerate breakup.