Dynamic simulation of sheared suspensions. I. General method

TLDR

The simulation framework distinguishes two procedures for computing particle interactions—pairwise additivity of forces or velocities—with the former preferred because it preserves hydrodynamic lubrication forces that prevent overlap. The study introduces a general method for simulating the dynamics of particle suspensions interacting via hydrodynamic and nonhydrodynamic forces. The two methods are compared in a simulation of a monolayer of identical rigid non‑Brownian spherical particles in a simple shear flow, using periodic boundary conditions to model an infinite suspension. Both methods predict a shear‑induced anisotropic local structure whose form and strength depend on particle concentration, non‑hydrodynamic forces, and shear rate, and increasing concentration up to the maximum flowing fraction leads to a layered structure with sliding planes, together implying non‑Newtonian rheology.

Abstract

A general method is presented for simulating the dynamical behavior of a suspension of particles which interact through both hydrodynamic and nonhydrodynamic forces. In the molecular-dynamics-like simulation there are two different procedures for computing the interactions among particles: a pairwise additivity of forces and a pairwise additivity of velocities. The pairwise additivity of forces is the preferred method as it preserves the hydrodynamic lubrication forces which prevent particles from overlapping. The two methods are compared in a simulation of a monolayer of identical rigid non-Brownian spherical particles in a simple shear flow. Periodic boundary conditions are used to model an infinite suspension. Both methods predict the presence of a shear induced anisotropic local structure whose form and strength depend on the concentration of particles, the nonhydrodynamic forces, and the shear rate. Increasing the particle concentration up to near the maximum fraction that can still flow results in a transition to a layered structure in which planes of particles slide relative to one another. The anisotropic local structure and transition to a layered structure predict a non-Newtonian suspension rheology.