(4ki) Colloidal Suspensions Under Imposed Flows and Fields: Controlling the Microscale Dynamics to Tune the Macroscopic Material Properties

Understanding the dynamics of rod-like particles under imposed flows is a fundamental problem in fluid mechanics with significant implications across various industrial sectors. The complex viscoelastic responses exhibited by colloidal rod suspension at semi-dilute concentrations are primarily governed by the flow-induced alignment of particles at the microscale. Despite extensive research on this topic since Jeffery's seminal work in 1922 on the dynamics of ellipsoidal particles in viscous fluids, the precise effects of hydrodynamic interactions (HI) between particles remain not well described. To address this gap, we employ numerical simulations based on the Brownian Dynamics method to explore the influence of HI on the rheology of semi-dilute colloidal rod suspensions. Our findings from this relatively simplistic model unveil a cascade effect wherein the tumbling of a single rod induces a disturbance in the flow, subsequently triggering the tumbling of neighboring particles and increasing the system’s viscosity.