Importance of convection in the compaction mechanisms of anisotropic granular media

TL;DR

This paper investigates how convection influences the compaction mechanisms in anisotropic granular media, revealing vortex patterns and the role of compression waves through experimental observations.

Contribution

It provides new experimental insights into vortex formation and the impact of convection on granular compaction, highlighting the significance of compression wave propagation.

Findings

High acceleration induces whole-media convection vortices.

Low acceleration results in unstable upper vortices and slow compaction.

Compression waves are crucial in granular compaction processes.

Abstract

We report the experimental observation of novel vortex patterns in a vertically tapped granular media. Depending on the tapping acceleration two behaviors are observed. For high acceleration a convection vortex appears in the whole media whereas for low acceleration two unstable vortices appear in the upper part of the media and slowly compact the lower part. We explain the formation of the vortices and relate them to granular convection. Our results demonstrate the importance of compression waves propagation on granular compaction.