Large scale dynamic simulation of plate-like particle suspensions. Part I: Non-Brownian simulation

Rheology and microstructure of plate-like particle suspensions in linear shear flows are studied through numerical simulations for a range of volume fraction φ up to 0.30. Particles with aspect ratio AR=3-7 are modeled as planar assemblages of spheres. Numerical methods are developed to calculate the hydrodynamic interactions based on an extension of the Stokesian dynamics method for spheres. At low φ, suspensions exhibit a degree of particle alignment consistent with the orientation distribution predicted by Jeffery orbits. At high φ, hydrodynamic interactions produce a high degree of ordering with particles aligned in horizontal layers perpendicular to the gradient direction. This allows sufficient free volume for shearing of the suspension with moderate viscosity at high φ. A second ordering mechanism is the formation of transient stacks of plate-like particles which move as rigid assemblies. The two mechanisms-particle alignment and particle stacking-reduce the effects of hydrodynamic interaction. Over the range of φ considered, viscosity is not a strong function of aspect ratio for non-Brownian suspensions, because the increased hydrodynamic interactions of high aspect ratio particles are offset by the increased degree of particle ordering.