Flow, Ordering and Jamming of Sheared Granular Suspensions

TL;DR

This study investigates the flow behavior of sheared granular suspensions, revealing flow regimes, order-disorder transitions, and jamming phenomena through molecular dynamics simulations.

Contribution

It introduces a phase diagram for granular suspensions under shear, detailing flow regimes, transitions, and jamming behavior based on volume fraction and stress.

Findings

Disordered flow at low volume fractions with Bagnold scaling.

Ordered flow regime at high volume fractions with sharp viscosity drop.

Identification of a broad jamming region with slow dynamics and kinetic arrest.

Abstract

We study the rheological properties of a granular suspension subject to constant shear stress by constant volume molecular dynamics simulations. We derive the system `flow diagram' in the volume fraction/stress plane $(\phi,F)$: at low $\phi$ the flow is disordered, with the viscosity obeying a Bagnold-like scaling only at small $F$ and diverging as the jamming point is approached; if the shear stress is strong enough, at higher $\phi$ an ordered flow regime is found, the order/disorder transition being marked by a sharp drop of the viscosity. A broad jamming region is also observed where, in analogy with the glassy region of thermal systems, slow dynamics followed by kinetic arrest occurs when the ordering transition is prevented.