# Discontinuous shear thickening of dense suspensions under confining pressure

## TL;DR

This study uses 2D simulations to analyze how confining pressure influences discontinuous shear thickening in dense suspensions, highlighting the role of frictional contacts and shear protocols.

## Contribution

It introduces a simple model linking frictional contact fraction to viscosity and jamming, revealing pressure-dependent shear thickening mechanisms.

## Key findings

- Viscosity diverges at a packing fraction controlled by frictional contacts.
- A relationship between frictional contacts, viscous number, and pressure ratio is established.
- Viscosity curves depend on shear protocol, with potential negative compressibility.

## Abstract

We use 2D numerical simulations to study dense suspensions of non-Brownian hard particles using the Critical Load Model (CLM) under constant confining pressures. This simple model shows discontinuous shear thickening (DST) as the tangential forces get activated upon increased shear stresses. By parameterizing a simple binary system of frictional and non-frictional particles of different proportions we show that the jamming packing fraction, at which the viscosity diverges, is controlled by the fraction of frictional contacts. The viscosity of dense suspensions can thereby be expressed as a function of the fraction of frictional contacts as well as the packing fraction of solid particles. In addition, we show that there exists a simple relationship between the fraction of frictional contacts and the two control parameters (under confining pressure): the viscous number J and the ratio between the repulsive barrier force and confining pressure. Under confining pressures the viscosity curves are found to depend on the shear protocol, with the possibility of yielding negative dynamic compressibility.