Rheology of dense vibrated granular flows: non-monotonic response controlled by granular temperature

TL;DR

This paper investigates how vertical vibrations influence the flow behavior of dense granular materials, revealing a non-monotonic viscosity response driven by the interplay of granular temperature and confinement effects.

Contribution

It introduces a framework linking granular temperature and confinement to rheological behavior, explaining previously observed viscosity and friction trends under vibration.

Findings

Viscosity increases with pressure and decreases with vibration amplitude.

Non-monotonic viscosity dependence on vibration frequency observed.

Granular temperature governs the rheological response.

Abstract

We study the rheology of dense granular materials subjected to vertical vibration {by} using numerical simulations of a stress-imposed vane rheometer. The effective viscosity increases with confining pressure, decreases with vibration amplitude, and exhibits a non-monotonic dependence on frequency: weakening is observed at intermediate frequencies but is lost at high frequencies. We show that the rheological response is governed by the balance between grain-scale agitation energy and the stabilizing effect of confinement. This framework reconciles previously observed trends in viscosity and friction weakening and emphasizes the central role of energy injection and dissipation in determining granular flow properties under vibration.