Structural evolution and breakage of dense agglomerates in shear flow and Taylor-Green vortex

Abstract

We perform adhesive discrete-element method (DEM) calculations to investigate the structural evolution and the breakage of dense agglomerates in a shear flow and a Taylor-Green vortex. By means of adhesive DEM, all possible modes of particle contacting interactions are resolved and the free-draining approximation is employed to calculate the hydrodynamic drag. We demonstrate that, for shear flows, dense agglomerates undergo significant restructuring before breakage. The normal force between contacting particles scales in a linear way as the shear rate increases. Based on extensive simulation results, a criterion for breakage is then proposed, which is valid across a wide range of shear stress and interparticle adhesion values. The average size of fragments at the quasi-steady state after the breakage follows a power function of a particle adhesion parameter. By defining an effective shear rate, we are able to extend the findings in simple shear flows to the breakage process in the vortex.