Brownian dynamics simulations of shear-induced aggregation of charged colloidal particles in the presence of hydrodynamic interactions

Hypothesis: In spite of the abundant literature on Brownian simulations of the aggregation behavior of colloidal suspensions both under quiescent conditions and in the presence of shear, few works performed simulations including the effect of hydrodynamic interactions. Even fewer works have investigated the effects of shear on the aggregation of electrostatically-stabilized colloidal suspensions.Simulations: In this work, we employed Brownian dynamics simulations implementing the Rotne-PragerYamakawa approximation to account for hydrodynamic interactions and investigated the aggregation kinetics of electrostatically-stabilized colloidal suspensions exposed to simple shear, for various Peclet number values, particle volume fractions and surface potential values.Results: The increase in Peclet number (i.e., in the shear rate), leads to an overall increase in the aggregation rate and the formation of large aggregates that, for sufficiently high volume fractions, rapidly grow, leading to either breakup and restructuring phenomena or percolation of the system. In some cases, a bimodal distribution of the cluster population was observed. Our simulations further indicate that at the highest Peclet, the aggregation dynamics is independent of the energy barrier and entirely controlled by shear. A comparison with a simple BD method reveals that neglecting long-range hydrodynamic interactions leads to a substantial underestimation of the aggregation rate.(c) 2022 The Author(s). Published by Elsevier Inc.

Automated summary

This work employs Brownian dynamics simulations to investigate the aggregation kinetics of electrostatically-stabilized colloidal suspensions exposed to simple shear. The results show that an increase in shear rate leads to an increase in aggregation rate and the formation of large aggregates. The simulations further indicate that at the highest shear rate, the aggregation dynamics is entirely controlled by shear.