On velocity profiles, stresses and Bagnold scaling of sheared granular system in zero gravity

TL;DR

This study uses 3D molecular dynamics simulations to analyze how boundary conditions affect velocity profiles, stresses, and Bagnold scaling in sheared granular systems in zero gravity, revealing boundary interaction effects and shear rate dependencies.

Contribution

It provides detailed insights into boundary effects, shear rate dependence, and Bagnold scaling in sheared granular systems under zero gravity conditions, using realistic boundary conditions.

Findings

Velocity profiles depend strongly on boundary interactions.

Frictional boundaries can cause particle slippage, reducing shear.

Stress and force fluctuations depend on shear rate and boundary conditions.

Abstract

We report the results of three-dimensional molecular dynamics simulations of sheared granular system in a Couette geometry.\cite{movies} The simulations use realistic boundary conditions that may be expected in physical experiments. For a range of boundary properties we report velocity and density profiles, as well as forces on the boundaries. In particular, we find that the results for the velocity profiles throughout the shearing cell depend strongly on the interaction of the system particles with the physical boundaries. Even frictional boundaries can allow for significant slippage of the particles, therefore, reducing the shear in the system. Next, we present shear rate dependence of stress, including mean force and force fluctuations, both for controlled volume, and for controlled stress configurations. We discuss the dependence of solid volume fraction on shear rate under the constant pressure condition, and Bagnold scaling in volume controlled experiments. In addition, we study the influence of oscillatory driving on the system properties.