# Experimental Characterization of the Hydrodynamic Interactions between a Freely Rising Bubble and a Settling Particle

## TL;DR

This paper studies how rising bubbles and settling particles interact in industrial systems, identifying four distinct interaction regimes.

## Contribution

The study introduces a new small-scale experimental method to classify bubble-particle collision regimes based on hydrodynamic forces.

## Key findings

- Four distinct interaction regimes (shuttling, bouncing, penetration, flotation) were identified based on collision outcomes.
- A robust image processing technique captured the 3D particle path during interactions.
- The method can capture regime transitions at higher particle concentrations or under varied parameters.

## Abstract

Bubble and particle interactions are fundamental in numerous
industrial
applications, particularly in the chemical and petrochemical industries,
where three-phase reactors and slurry bubble columns are widely employed.
Characterizing these interactions is inherently complicated as the
mobility of the settling particle is coupled with the deformable nature
of the rising bubble. This study attempts to unravel this complex
system by developing a small-scale experimental approach to investigate
and classify the different collision regimes. By utilizing a robust
in-house image processing technique, we extracted the three-dimensional
(3D) path of the particle during the interaction. A hydrodynamic force
analysis method is applied to investigate the force balance exerted
on the particle and the impulse variation during the interaction.
Four distinguished regimes, called shuttling, bouncing, penetration,
and flotation, are identified by the outcomes of the collision, based
on hydrodynamic force balance. This approach can capture the transition
between the different regimes at even higher particle concentrations
or under different systematic parameters. These results provide fundamental
insights into the bubble–particle interactions, offering a
basis for developing scaled-up numerical models for the real-sized
three-phase bubble columns.