The Flow Of Granular Matter Under Reduced-Gravity Conditions

TL;DR

This study investigates how granular materials flow under reduced gravity conditions using experiments in a drop tower and centrifuge, providing insights relevant to planetary surface processes.

Contribution

It presents new experimental data on granular flow behavior at low gravity levels using innovative setups like an hourglass and avalanche box.

Findings

Flow rate decreases with lower gravity

Repose and friction angles vary with gravity

Avalanche duration and slope depend on gravity level

Abstract

To gain a better understanding of the surfaces of planets and small bodies in the solar system, the flow behavior of granular material for various gravity levels is of utmost interest. We performed a set of reduced-gravity measurements to analyze the flow behavior of granular matter with a quasi-2D hourglass under coarse-vacuum conditions and with a tilting avalanche box. We used the Bremen drop tower and a small centrifuge to achieve residual-gravity levels between 0.01 g and 0.3 g. Both experiments were carried out with basalt and glass grains as well as with two kinds of ordinary sand. For the hourglass experiments, the volume flow through the orifice, the repose and friction angles, and the flow behavior of the particles close to the surface were determined. In the avalanche-box experiment, we measured the duration of the avalanche, the maximum slope angle as well as the width of the avalanche as a function of the gravity level.