Block to granular-like transition in dense bubble flows

TL;DR

This study experimentally explores the transition in dense bubble flows on inclined planes, revealing a phase change from block motion to shear flow as the tilt angle increases, characterized by velocity profiles and fluctuations.

Contribution

It identifies and characterizes a second-order phase transition in dense bubble flows, linking flow regimes to tilt angle and providing detailed velocity measurements.

Findings

Transition from block to shear flow with increasing tilt angle

Velocity profiles change from flat to curved

Velocity fluctuations increase near transition

Abstract

We have experimentally investigated 2-dimensional dense bubble flows underneath inclined planes. Velocity profiles and velocity fluctuations have been measured. A broad second-order phase transition between two dynamical regimes is observed as a function of the tilt angle $\theta$. For low $\theta$ values, a block motion is observed. For high $\theta$ values, the velocity profile becomes curved and a shear velocity gradient appears in the flow.