Microstructure and rheology of rim-charged platelike particle suspensions: A numerical study

This article investigates the effect of rim charges on the macroscopic flow behavior of platelike particle suspensions in Couette flow. Fluid-solid coupling is achieved using the lattice spring direct-forcing immersed boundary lattice Boltzmann method. Platelike particles are equipped with rim charges to simulate the inhomogeneous charge distribution commonly observed in clay particles. By examining suspensions with varying numbers of platelike particles, it has been found that rim charges induce particle clustering in shear flow. At low shear rates, inter-particle electrostatic forces drive the formation of large clusters, resulting in higher suspension viscosity. As the shear rate increases, hydrodynamic forces break large clusters into smaller ones, leading to a decrease in shear viscosity. Orientation correlation function calculations indicate that rim charges on platelike particles promote the formation of house-of-cards (HoC) microstructures in suspensions, and these microstructures transform from HoC-dominant to overlapping coins-dominant as shear flow grows stronger. Additionally, investigations of suspensions with larger aspect ratios reveal that the average cluster volume is the primary factor influencing the viscosity of rim-charged platelike particle suspensions, especially under conditions where electrostatic forces dominate. Our results provide insights into the relationship between particle clusters and macroscopic flow properties in clay systems.