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, \Revision{consistent with coherent translation within rigid clusters and a state-dependent contrast in relative motion between particles inside and outside them}. Rotational motion provides a complementary view: non-affine angular-velocity distributions broaden, \Revision{near-contact non-affine rotational fluctuations become increasingly anti-correlated, and particles inside and outside rigid clusters 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.