Density waves in dry granular media falling through a vertical pipe

TL;DR

This paper experimentally investigates the formation of density waves in dry granular media flowing through a vertical pipe, revealing a specific flow regime where these waves occur at intermediate flow rates.

Contribution

It introduces experimental observations of density waves in granular flow within a capillary tube, highlighting the flow conditions that lead to wave formation.

Findings

Density waves occur at intermediate flow rates.

Flow regimes are characterized by transitions from free fall to slow, dense flow.

Experimental data delineate the conditions for density wave formation.

Abstract

We report experimental measurements of density waves in granular materials flowing down in a capillary tube. The density wave regime occurs at intermediate flow rates between a low density free fall regime and a high compactness slower flow.