Radial segregation driven by axial convection

TL;DR

This paper investigates how axial convection influences radial segregation in granular systems within a rotating cylinder, revealing that differences in dynamic angle of repose and density affect segregation dynamics and steady states.

Contribution

It introduces a new mechanism where axial differences in dynamic angle of repose promote radial segregation, differing from previous free surface segregation explanations.

Findings

Axial transport causes transient radial segregation when particles differ only by repose angle.

Radial segregation becomes steady when particles also differ by density.

Radial segregation is driven by axial differences in dynamic angle of repose.

Abstract

We experimentally study the mixing of binary granular systems in a horizontal rotating cylinder. When materials have the same size and differ by dynamic angle of repose only, we observe an axial transport of matter that generates transient radial segregation. The system then evolves towards homogeneity. If materials differ by density also radial segregation becomes steady. A mechanism is suggested where radial segregation is promoted by axial differences of dynamic angle of repose. This differs from the free surface segregation suggested so far to explain radial segregation.