Unravelling bubble-particle collisions in turbulence

ongoing

The objective of the proposed study program is to elucidate the effect of turbulence on collisions between bubbles and particles. Such collisions are fundamental to flotation, a process widely used to separate materials based on differences in their hydropThe objective of the proposed study program is to elucidate the effect of turbulence on collisions between bubbles and particles. Such collisions are fundamental to the flotation process, a technology widely used in industry. Applications include wastewater treatment, paper recycling, and especially mining, where flotation is used to separate minerals. This process commonly operates under strongly turbulent conditions and the important role of turbulence is now a widely accepted fact in the mineral engineering community. The actual effect of turbulence on the bubble-particle collision rate, however, remains unclear. This is largely because effects arising from a finite drift velocity of suspended species, such as preferential concentration, remain entirely unexplored and hence unaccounted for. Bubbles and light particles behave fundamentally different in a turbulent flow compared to their heavy counterparts and therefore the problem. Therefore the bubble-particle problem is fundamentally different from e.g. droplet collisions in clouds, requiring new concepts. I intend to investigate bubble-particle collisions through combined experimental and numerical efforts. Experiments using Particle Tracking Velocimetry will provide much needed reference data while direct numerical simulations via point-particle and immersed-boundary methods will allow us to study various physical effects in detail. Together, these will enable us to develop and test realistic theories and models for the geometric collision rate between particles and bubbles as well as for their collision efficiency. The ultimate goal is a physics-based parametrization of the effective bubble-particle collision rate in realistic conditions.