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

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.