Spontaneous jamming and unjamming in a hopper with multiple exit orifices

TL;DR

This study investigates how multiple exit orifices in a 2D hopper influence granular flow, revealing that inter-orifice interactions can significantly enhance flow and avalanche size through jamming and unjamming dynamics.

Contribution

The paper demonstrates that multiple orifices can increase granular flow efficiency and elucidates the mechanisms of unjamming driven by fluctuations and mean flow.

Findings

Avalanche size can be increased by about tenfold with optimal orifice spacing.

Intermittent flow enables unjamming of jammed orifices.

Fluctuations alone can cause unjamming at large inter-orifice distances.

Abstract

We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For the hoppers with small orifice widths, inter-mittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e. avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the inter-orifice distance. The unjamming is driven primarily by fluctuations alone when the inter-orifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow unjamming.