Piling and avalanches of magnetized particles

TL;DR

This study uses computer simulations to explore how magnetization influences the stability and avalanche behavior of granular particle piles, revealing a transition from continuous flow to clustered avalanches at a critical magnetic interaction ratio.

Contribution

It introduces a detailed simulation analysis of magnetized granular piles, identifying a transition point and characterizing different avalanche regimes based on magnetic forces.

Findings

Angle of repose and surface roughness increase linearly with magnetic interaction ratio.

A transition from granular to correlated avalanche regimes occurs at f_c ≈ 7.

The transition is gradual, not abrupt.

Abstract

We performed computer simulations based on a two-dimensional Distinct Element Method to study granular systems of magnetized spherical particles. We measured the angle of repose and the surface roughness of particle piles, and we studied the effect of magnetization on avalanching. We report linear dependence of both angle of repose and surface roughness on the ratio $f$ of the magnetic dipole interaction and the gravitational force (\emph{interparticle force ratio}). There is a difference in avalanche formation at small and at large interparticle force ratios. The transition is at $f_c \approx 7$. For $f < f_c$ the particles forming the avalanches leave the system in a quasi-continuous granular flow (\emph{granular regime}), while for $f > f_c$ the avalanches are formed by long particle clusters (\emph{correlated regime}). The transition is not sharp. We give plausible estimates for $f_c$ based on stability criteria.