Dynamics and rheology of concentrated, finite-Reynolds-number suspensions in a homogeneous shear flow

Abstract

We present the lubrication-corrected force-coupling method for the simulation of concentrated suspensions under finite inertia. Suspension dynamics are investigated as a function of the particle-scale Reynolds number Reγ and the bulk volume fraction φ{symbol} in a homogeneous linear shear flow, in which Reγ is defined from the density ρf and dynamic viscosity μ of the fluid, particle radius a, and the shear rate γ as Reγ=ρfγa2/μ. It is shown that the velocity fluctuations in the velocity-gradient and vorticity directions decrease at larger Reγ. However, the particle self-diffusivity is found to be an increasing function of Reγ as the motion of the suspended particles develops a longer auto-correlation under finite fluid inertia. It is shown that finite-inertia suspension flows are shear-thickening and the particle stresses become highly intermittent as Reγ increases. To study the detailed changes in the suspension microstructure and rheology, we introduce a particle-stress-weighted pair-distribution function. The stress-weighted pair-distribution function clearly shows that the increase of the effective viscosity at high Reγ is mostly related to the strong normal lubrication interaction in the compressive principal axis of the shear flow. © 2013 AIP Publishing LLC.