The Wrath of the Small: Fragmentation of Bubbles in Turbulence by Small Eddies
From milk homogenization to whitecaps in the ocean, fragmentation of bubbles and droplets in turbulence constitutes one of the most basic and practically important processes in turbulent multiphase flows. Most phenomenological models and simulations for this problem were developed based on the classical Kolmogorov-Hinze framework, even though some of the key assumptions and hypotheses in this framework have never been tested. In this talk, I will first introduce a new experimental framework that measures the geometry of deforming and breaking bubbles and their surrounding turbulence simultaneously in 3D. From this new result, I will discuss two issues that we found in the classical framework: (i) the Kolmogorov’s classical theory of turbulence is not sufficient for quantifying the turbulent stresses exerted on the bubble interface, and (ii) the assumption that the most relevant and energetic scale of the flow is at the bubble diameter underestimates the roles played by small eddies. Our work underlines the importance of two missing mechanisms and paves the foundation for future studies on the dynamics of polydispersed bubbles and droplets in turbulence.
