Structural evolution of fractal particle agglomerates in a Taylor-Green vortex

Micron particles generally exist in the form of agglomerates, such as those in pulverized coal combustion, electrostatic agglomerators and flocculation during water treatment. Prediction of the structure of agglomerate in the flow field is a crucial but highly challenging problem. In this work, the structural evolution of agglomerates in a pseudo 2D Taylor-Green vortex is numerically investigated using an adhesive discrete-element method. We focus on the influence of the initial agglomerate structure, the interparticle adhesive force and flow field parameters on the structure of agglomerates. We find that loosely-packed agglomerates become more compact in the region with a higher shear rate. A stronger interparticle adhesion and a more compact structure both hinder the breakage and restructuring of the agglomerates. Based on an extensive simulation runs, we present a phase diagram in the form of the flow shear rate and the interparticle adhesion to summarize all possible deformation modes for an agglomerate in a vortex.