Experimental and theoretical study on the fundamental processes controlling bubble interactions with hydrophobic particles in turbulent flow

• Applicant: Dr.-Ing. Tian Ma
• Subject Area: Fluid Mechanics ; Energy Process Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555712173

Understanding bubble-particle interactions in turbulent flows is of broad interest as a general problem in the science of multiphase flows and is important for many technological processes. One such example is the flotation process where gas bubbles are dispersed into the pulp, and hydrophobic particles that become attached to the bubbles can then rise to the top of the cell where the froth can be skimmed off and the valuable particles extracted. The effectiveness of the process depends crucially on the ability of the particles to come into contact with the bubble surfaces in the first place, and then once there, remaining attached for long enough to rise to the top of the cell. The impact of turbulence on these factors is unclear, and there remain many fundamental questions that are mostly unexplored: what are the physical mechanisms by which turbulent fluctuations control particle fluxes towards and away from the bubble surfaces? What is the collision rate of the particles on the bubble surfaces, and how probable is it that a particle which is attached will be attached for long enough to rise to the top of the flotation cell? In what parameter regimes does the turbulence that is produced by the moving bubbles help or hinder the particle attachment/detachment process? What is the impact of surfactants in the flow? In the proposed investigation, we will conduct revolutionary three-dimensional (3D) Lagrangian particle tracking measurements for tracers, inertial particles and bubbles in a turbulent column. For the carrier phase, the experiments will explore the impact of the bubbles, surfactants, and particles on the properties of the carrier flow turbulence. For the dispersed phase, we will use the experimental data to conduct a detailed investigation into the bubble-particle mixing and dispersion, the mass flux of particles to and from the bubble surfaces, and the dependence of this on the flow parameters. The work will lead to transformative insights into the physics of multiphase turbulent flows involving interactions between bubbles and particles. These advances will then provide crucial insights for the design of multiphase flow devices in engineered contexts, such as the flotation process.

• DFG Programme: Research Grants
• International Connection: USA
• Co-Investigators: Dr.-Ing. Hendrik Hessenkemper; Dr.-Ing. Anna-Elisabeth Sommer
• Cooperation Partner: Professor Andrew Bragg, Ph.D.