Boundary Effects on the Angle of Repose in Rotating Cylinders

TL;DR

This study investigates how boundary effects influence the angle of repose in granular flow within rotating cylinders through experiments and simulations, revealing how wall influence scales with drum size and particle properties.

Contribution

It introduces a quantitative analysis of boundary effects on the angle of repose, including the characteristic range of wall influence and its dependence on system parameters.

Findings

The wall influence range scales with drum radius.

The influence range does not depend on particle density or gravity.

Finite size effects become apparent with larger particles.

Abstract

The angle of repose for the flow of granular materials in a half-filled rotating drum is studied by means of experiments and computer simulations. Particles of different material properties are used to investigate the effects of the end caps on the angle of repose. By fitting the numerical results to an exponentially decaying function, we are able to calculate the characteristic range, $\zeta$, of the influence of the wall. We found that $\zeta$ scales with the drum radius but does not depend on either the density or the gravitational constant. For increasing particle diameter, finite size effects are visible.