Shear thickening in non-Brownian suspensions: an excluded volume effect

TL;DR

This paper explains shear thickening in non-Brownian suspensions as a consequence of inertia-induced microstructure anisotropy and the formation of shadow regions that effectively increase the volume fraction.

Contribution

It introduces a novel explanation for shear thickening based on excluded volume effects caused by inertia-induced shadow regions.

Findings

Inertia causes microstructure anisotropy in suspensions.

Shadow regions with no particle flux form at finite inertia.

Shear thickening can be explained by increased effective volume fraction.

Abstract

Shear thickening appears as an increase of the viscosity of a dense suspension with the shear rate, sometimes sudden and violent at high volume fraction. Its origin for noncolloidal suspension with non-negligible inertial effects is still debated. Here we consider a simple shear flow and demonstrate that fluid inertia causes a strong microstructure anisotropy that results in the formation of a shadow region with no relative flux of particles. We show that shear thickening at finite inertia can be explained as an increase of the effective volume fraction when considering the dynamically excluded volume due to these shadow regions