Long lasting instabilities in granular mixtures

TL;DR

This paper investigates long-lasting instabilities in granular mixtures during axial segregation, revealing that competition between axial and radial segregation causes prolonged fluctuations and giant surface composition variations.

Contribution

It provides experimental evidence of persistent instabilities and giant fluctuations in granular segregation, highlighting the complex dynamics between axial and radial segregation mechanisms.

Findings

Instabilities can last several hours.

Giant fluctuations occur in grain composition.

Competition between axial and radial segregation drives instability.

Abstract

We have performed experiments of axial segregation in the Oyama's drum. We have tested binary granular mixtures during very long times. The segregation patterns have been captured by a CCD camera and spatio-temporal graphs are created. We report the occurence of instabilities which can last several hours. We stress that those instabilities originate from the competition between axial and radial segregations. We put into evidence the occurence of giant fluctuations in the fraction of grain species along the surface during the unstable periods.