Simulation of aggregating colloids in shear flow

Abstract

Computer simulation is carried out for the kinetics of aggregating colloids in shear flow. The colloidal particles are assumed to form a cluster when they touch. The clusters can deform, rupture, and aggregate with other clusters. The motion of the clusters is determined by solving the equation of motion of individual particles. Cluster size and macroscopic viscosity are calculated as a function of shear rate and particle concentration. It is found that (i) at low concentration the particles form compact clusters, while at high concentration they form loose networks, and that (ii) despite the change in the cluster type, the steady state viscosity obeys the same power law for all concentrations. These results suggest that the key structural parameter governing the macroscopic viscosity is not the size of the clusters, but the size of the flowing unit which is a rigid block in the cluster.