Three-dimensional shear in granular flow

TL;DR

This study investigates how shear behavior in granular flow changes with height in a split-bottom Couette cell, revealing a transition from a stationary core to axial shear as height exceeds a critical value.

Contribution

It identifies a transition in shear dynamics in granular flow, combining experimental and simulation data to characterize the change at a specific height.

Findings

Presence of a stationary core below a critical height

Onset of axial shear beyond the critical height

Radial shear extent increases with height, axial shear remains narrow

Abstract

The evolution of granular shear flow is investigated as a function of height in a split-bottom Couette cell. Using particle tracking, magnetic-resonance imaging, and large-scale simulations we find a transition in the nature of the shear as a characteristic height $H^*$ is exceeded. Below $H^*$ there is a central stationary core; above $H^*$ we observe the onset of additional axial shear associated with torsional failure. Radial and axial shear profiles are qualitatively different: the radial extent is wide and increases with height while the axial width remains narrow and fixed.