Distribution of forces and 'hydrodynamic clustering' in a shear thickened colloid

Abstract

Sheared concentrated colloids with short range polymer coats are examined via simulations. Distributions of force are found to be sums of exponentials. The 'hydrodynamic clustering' underlying the shear thickening effect is shown, in this system, to be a network of percolating coat contacts, with coats both in compression and extension. The geometry and kinetics of this network are explored along with its relation to the bulk stress tensor. Particles experience strong fluctuations in force over epochs $\it{circa}$ 10% strain. Density fluctuations up to glassy volume fractions give rise to scattering peaks at low Q in the thickening regime. There is some commonality in the physics of this colloid particulate system and other granular media.