On the use of magnetic particles to enhance the flow of vibrated grains through narrow apertures

TL;DR

This study investigates how adding self-repelling magnetic particles affects the flow of grains through narrow openings, revealing that magnetic additives do not always improve flow as previously assumed.

Contribution

It provides new insights into the role of magnetic particles in granular flow, challenging the idea that they universally facilitate unclogging.

Findings

Magnetic particles do not always enhance flow in granular materials.

Adding magnetic grains can sometimes hinder rather than help flow.

The effect depends on the specific interactions between particles.

Abstract

The flow of grains through narrow apertures posses an extraordinary challenge: clogging. Strategies to alleviate the effect of clogging, such as the use of external vibration, are always part of the design of machinery for the handling of bulk materials. It has recently been shown that one way to reduce clogging is to use a small fraction of small particles as an additive. Besides, several works reported that self-repelling magnetic grains can flow through narrow apertures with little clogging, which suggest these are excellent candidates as "lubricating" additives for other granular materials. In this work, we study the effect of adding self-repelling magnetic particles to a sample of grains in two-dimensions. We find that, in contrast with intuition, the added magnetic grains not necessarily aid the flow of the original species.