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

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 Re-(gamma) over dot and the bulk volume fraction phi in a homogeneous linear shear flow, in which Re-(gamma) over dot is defined from the density rho(f) and dynamic viscosity mu of the fluid, particle radius a, and the shear rate (gamma) over dot as Re-(gamma) over dot = rho(f)(gamma) over dota(2)/mu. It is shown that the velocity fluctuations in the velocity-gradient and vorticity directions decrease at larger Re-(gamma) over dot However, the particle self-diffusivity is found to be an increasing function of Re-(gamma) over dot 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 Re-(gamma) over dot 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 Re-(gamma) over dot is mostly related to the strong normal lubrication interaction in the compressive principal axis of the shear flow. (C) 2013 AIP Publishing LLC.