Structural Evolution Under Shear In Brownian Suspensions

Shear-induced ordering is known to occur in sheared suspensions. Here we probe the range of parameters for which this order occurs by simulation of Brownian hard-sphere suspensions using Accelerated Stokesian Dynamics. The suspensions are found to undergo ordering over extended periods at the onset of flow, with remarkable reduction in the shear viscosity and self-diffusivity observed upon ordering into chains with hexagonal packing in the plane normal to the flow. The simulations are performed at various Peclet numbers, Pe, (relative strength of shear to Brownian forces) for particle volume fractions 0.47 ≤ φ ≤ 0.57. The microstructural properties of the system are studied based on analysis of both the pair distribution function and the static structure factor. The transition for ordering has been identified as roughly Pe = 10 and φ = 0.50. At Pe ≥ 10, the microstructural measures indicate that particles progressively tend to flow in chains for φ > 0.50, while no such ordering is observed at Pe = 1.