Microstructure and rheology of dense frictionless non-Brownian suspensions

Discrete element simulations are used to characterize the microstructure and rheology of concentrated non-Brownian suspensions of spheres in which short-range repulsive forces prevent the formation of direct frictional contacts and limit the strength of lubrication interactions. Ball and Melrose (1994 & 1995) showed that sheared suspensions of smooth spheres with purely hydrodynamic interactions form particle clusters with increasingly smaller interparticle distances and stronger lubrication forces eventually arresting the motion of the suspension for any finite imposed stress. This paper will examine the finite particle cluster sizes and the resulting particle velocity correlation functions that arise in the presence of short-range repulsive forces. We will characterize the mechanisms by which clusters form and evolve, providing insight into the flow-microstructure relationship. We will also consider how stresses are transmitted across a cluster through normal repulsive forces and both normal and tangential lubrication forces contributing to the bulk rheological response and its dependence on volume fraction and the range of the interparticle repulsion.

References:

Ball and Melrose, Proc. of INDO U.K. forum (1994).

Melrose and Ball, Europhys. Lett., 32 (6), pp. 535-540 (1995)