Unjamming a granular hopper by vibration

TL;DR

This experimental study demonstrates that vibrations can significantly reduce jamming in granular hoppers, allowing flow through smaller openings and revealing complex flow behaviors influenced by vibration amplitude.

Contribution

It provides new insights into how vibrations affect granular flow and jamming limits, extending the understanding of flow behavior down to a single grain diameter.

Findings

Flow persists down to one grain diameter with vibration.

Flow rate remains largely unaffected by vibration.

Flow time increases with vibration amplitude.

Abstract

We present an experimental study of the outflow of a hopper continuously vibrated by a piezoelectric device. Outpouring of grains can be achieved for apertures much below the usual jamming limit observed for non vibrated hoppers. Granular flow persists down to the physical limit of one grain diameter, a limit reached for a finite vibration amplitude. For the smaller orifices, we observe an intermittent regime characterized by alternated periods of flow and blockage. Vibrations do not significantly modify the flow rates both in the continuous and the intermittent regime. The analysis of the statistical features of the flowing regime shows that the flow time significantly increases with the vibration amplitude. However, at low vibration amplitude and small orifice sizes, the jamming time distribution displays an anomalous statistics.