Dense bubble flow in a silo: an unusual flow of a dispersed medium

TL;DR

This study investigates the dense flow of air bubbles in a liquid-filled silo, revealing similarities to granular flow, a new discharge law, and the influence of bubble deformability on flow behavior.

Contribution

It introduces a novel Beverloo-like discharge law for bubble flow in silos and explores the relationship between bubble deformation and velocity.

Findings

Flow rate varies as D^{1/2}

Flow behavior resembles granular flow

Deformability affects bubble velocities

Abstract

The dense flow of air bubbles in a two-dimensional silo (through an aperture D) filled with a liquid is studied experimentally. A particle tracking technique has been used to bring out the main properties of the flow: displacements of the bubbles, transverse and axial velocities. The behavior of the air bubbles is observed to present similarities with non-deformable solid grains in a granular flow. Nevertheless, a correlation between the bubble velocities and their deformations has been evidenced. Moreover, a new discharge law (Beverloo-like) must be considered for such a system, where the flow rate is observed to vary as D^{1/2} and depends on the deformability of the particles.