# On the brink of jamming: Granular convection in densely filled containers

## TL;DR

This study investigates granular convection in densely filled containers using a Hele-Shaw cell, revealing a transition from chute flow to convection as fill level increases, highlighting complex dynamics in granular materials.

## Contribution

It demonstrates the emergence of convection and segregation in densely packed granular systems under slow rotation, a phenomenon less understood compared to liquids.

## Key findings

- Transition from chute flow to convection with increasing fill level
- Convection rolls and segregation observed in densely filled containers
- Dynamic regimes depend critically on container fill level

## Abstract

Granulates are ubiquitous in nature and technology, but despite their great importance, their dynamics are by far less well understood than those of liquids. We demonstrate in an almost compactly filled flat (Hele-Shaw) cell, where slow horizontal rotation simulates a variable gravitational force, that unexpected dynamic structures may arise under geometrical restrictions. The cell motion drives regular flow in the compact interior, and convection rolls combine with segregation. The container fill level is crucial for the dynamic regime. A transition from chute flow at lower fill levels to convection in densely packed containers is found. These observations suggest the existence of comparable phenomena in situations where so far no systematic search for dynamic patterns has been performed.