Shear thickening regimes of dense non-Brownian suspensions

TL;DR

This paper introduces a comprehensive rheological model for dense non-Brownian suspensions, identifying distinct shear thickening mechanisms due to particle friction and inertia, supported by simulations and microstructural analysis.

Contribution

It presents a unifying framework predicting shear thickening regimes and their microstructural transitions, validated by discrete element simulations.

Findings

Identifies particle friction and inertia as separate shear thickening mechanisms.

Demonstrates concurrent occurrence of both mechanisms under specific conditions.

Shows microstructural divergences in thickened and non-thickened states.

Abstract

We propose a unifying rheological framework for dense suspensions of non-Brownian spheres, predicting the onsets of particle friction and particle inertia as distinct shear thickening mechanisms, while capturing quasistatic and soft particle rheology at high volume fractions and shear rates respectively. Discrete element method simulations that take suitable account of hydrodynamic and particle-contact interactions corroborate the model predictions, demonstrating both mechanisms of shear thickening, and showing that they can occur concurrently with carefully selected particle surface properties under certain flow conditions. Microstructural transitions associated with frictional shear thickening are presented. We find very distinctive divergences of both the microstructural and dynamic variables with respect to volume fraction in the thickened and non-thickened states.