Contact-network organization and motion statistics in shear-thickening suspensions

Abstract

We use lubricated-flow discrete-element-method (LF-DEM) simulations to examine how contact-network organization shapes particle motion in dense shear-thickening suspensions. The primary system studied is a two-dimensional bidisperse monolayer where rigid clusters are identified by the $(3,3)$ pebble game; three-dimensional simulations are shown to have qualitatively similar rotational velocity statistics. Across the stress--solid-fraction state diagram, frictional contact number, $k\ge 3$ percolation, and rigid-cluster fluctuations all strengthen in the same region where translational velocity correlations grow, consistent with rigid clusters translating coherently while the surrounding non-rigid particles accommodate a disproportionate share of the local velocity gradient. Rotational motion provides a complementary view: non-affine angular-velocity distributions broaden, near-contact rotations become increasingly anti-correlated, and rigid and non-rigid particles carry distinct statistics. Connectivity, rigidity, and velocity correlations are related but distinct signatures of the constrained collective motion that accompanies shear-thickening and the approach to shear jamming.