Flow regimes and repose angle in a rotating drum filled with highly concave particles

TL;DR

This study investigates how particle shape, friction, and rotation speed influence flow regimes and repose angles in a rotating drum filled with highly concave granular particles, revealing two main flow behaviors and their phase boundaries.

Contribution

It introduces a comprehensive experimental analysis of flow regimes in granular materials with varying concavity and friction, establishing phase diagrams and quantitative criteria for regime transitions.

Findings

Identified two distinct flow regimes: rolling and slumping.

Constructed phase diagrams based on repose angle difference and area ratio.

Demonstrated the impact of particle concavity and friction on flow behavior.

Abstract

We present a series of experiments investigating the flow regimes and repose angles of highly concave particle packings in a rotating drum. By varying grain geometry from spherical to highly non-convex shapes, adjusting frictional properties and the particle number of branches, we examine how these parameters and the drum speed influence the flow behavior. Our study identifies two distinct flow regimes: the rolling regime, where granular matter exhibits solid-like behavior near the walls and flows like a liquid near the free surface, and the slumping regime, characterized by cyclic avalanches and solid body rotations. Using quantitative criteria such as the repose angle difference and the area ratio of particle packings, we construct phase diagrams delineating the cross-over between these regimes. Our findings highlight the significant effects of particle concavity, friction, and rotation speed on the flow dynamics of granular materials, providing new insights into the mechanical behaviors of \emph{meta-granular matter}.