Effect of turbulence intensity on the capture behavior of different sizes bubbles within a confined vortex flow field

The detachment of bubble–particle aggregates induced by turbulence is a major factor contributing to the low recovery of coarse particles in flotation. Thus, clarifying the interaction mechanisms between bubble–particle aggregates and turbulent flow structures is crucial for reducing detachment probability and improving flotation efficiency. Most existing studies implicitly assume that bubble–particle aggregates are already captured by vortical structures and mainly focus on vortex-induced detachment mechanisms, while the capture process itself has not been systematically investigated. In the present study, a customized confined vortex generation system was developed, and high-speed imaging combined with particle image velocimetry (PIV) was used to systematically investigate the effects of turbulence intensity on the capture behavior of bubbles with different sizes. The results show that the bubble transport and capture are governed by the competition between buoyancy and pressure-gradient forces: when buoyancy dominates, bubbles tend to rise and escape from the vortex; conversely, when the pressure-gradient force prevails, bubbles are captured into the central region of the cavity and exhibit periodic circular motion. Further analysis of the bubble capture probability and turbulence scales indicates that the vortex capture of bubbles is primarily controlled by eddies at the Taylor scale. Based on this finding, a critical bubble size—Taylor-scale predictive model—was established using the Hoffman model, enabling a quantitative correlation between turbulence structural parameters and bubble transport behavior. This study elucidates the scale-selective mechanism of bubble capture by turbulent vortices and provides new theoretical insights and design guidance for bubble regulation and process intensification in flotation systems.