Granular Shear Flow in Varying Gravitational Environments

TL;DR

This study investigates how granular materials on asteroids respond to shear forces in microgravity, revealing that shear band formation is not significantly affected by low gravity conditions, which is crucial for asteroid exploration.

Contribution

The paper presents a novel experimental setup for studying granular shear flow in microgravity and demonstrates that shear band formation occurs similarly across different gravitational environments.

Findings

Shear bands form in microgravity similarly to Earth.

Granular flow behavior is weakly influenced by gravity.

Experimental design tailored for parabolic flight conditions.

Abstract

Despite their very low surface gravities, asteroids exhibit a number of different geological processes involving granular matter. Understanding the response of this granular material subject to external forces in microgravity conditions is vital to the design of a successful asteroid sub-surface sampling mechanism, and in the interpretation of the fascinating geology on an asteroid. We have designed and flown a Taylor-Couette shear cell to investigate granular flow due to rotational shear forces under the conditions of parabolic flight microgravity. The experiments occur under weak compression. First, we present the technical details of the experimental design with particular emphasis on how the equipment has been specifically designed for the parabolic flight environment. Then, we investigate how a steady state granular flow induced by rotational shear forces differs in varying gravitational environments. We find that the effect of constant shearing on the granular material, in a direction perpendicular to the effective acceleration, does not seem to be strongly influenced by gravity. This means that shear bands can form in the presence of a weak gravitational field just as on Earth.