Viscous-inertial transition in dense granular suspension

TL;DR

This study investigates the transition from viscous to inertial rheology in dense granular suspensions, revealing a consistent Stokes number at transition and exploring stress additivity to unify rheological regimes.

Contribution

It introduces a systematic experimental analysis of the viscous-inertial transition near jamming, highlighting the role of the Stokes number and stress additivity in rheology.

Findings

Transition occurs at Stokes number of 10, independent of packing fraction.

Inertial and viscous regimes can be unified through stress additivity.

Experimental rheometry confirms rheological transition near jamming.

Abstract

Granular suspensions present a transition from a Newtonian rheology in the Stokes limit to a Bagnoldian rheology when inertia is increased. A custom rheometer which can be run in a pressure or a volume-imposed mode is used to examine this transition in the dense regime close to jamming. By varying systematically the interstitial fluid, shear rate, and packing fraction in volume-imposed measurements, we show that the transition takes place at a Stokes number of 10 independent of the packing fraction. Using pressure-imposed rheometry, we investigate whether the inertial and viscous regimes can be unified as a function of a single dimensionless number based on stress additivity.