Transients in shear thickening suspensions: when hydrodynamics matters

TL;DR

This study uses particle-based simulations to explore how transient dilation affects shear thickening suspensions near shear jamming, revealing finite stress levels governed by particle network dilation and backflow, with implications for modeling inhomogeneous flows.

Contribution

It introduces a continuum model that captures transient dilation dynamics and stress behavior in shear thickening suspensions, extending understanding beyond steady-state rheology.

Findings

Stress levels remain finite during shear jamming, contrary to divergence predictions.

Stress gradients scale quadratically with system size, indicating inhomogeneous flow effects.

A continuum model accurately predicts stress behavior based on dilation and backflow coupling.

Abstract

Using particle-based numerical simulations performed under pressure-imposed conditions, we investigate the transient dilation dynamics of a shear thickening suspension brought to shear jamming. We show that the stress levels, instead of diverging as predicted by steady state flow rules, remain finite and are entirely determined by the coupling between the particle network dilation and the resulting Darcy backflow. System-spanning stress gradients along the dilation direction lead to cross-system stress differences scaling quadratically with the system size. Measured stress levels are quantitatively captured by a continuum model based on a Reynolds-like dilatancy law and the Wyart-Cates constitutive model. Beyond globally jammed suspensions, our results enable the modeling of inhomogeneous flows where shear jamming is local, e.g. under impact, which eludes usual shear thickening rheological laws.