CAREER: Bubble fragmentation in turbulent flows

点击翻译按钮获取中文摘要

Bubble break up in turbulent flows is important in many environmental and industrial situations. These include oil spill mitigation, air entrained in bow waves in ships and submarines, and ocean-atmosphere interactions associated with breaking waves. The bubble interface may deform and break violently under the action of turbulent flows, and the newly formed interfaces dramatically increase transfer of heat and mass between the gas and liquid phases. This award describes a series of state-of-the-art numerical and experimental studies of the fragmentation of bubbles in turbulent flow. The goal is to produce a general model that describes the roles of turbulent flow and the interface properties on the rupture of bubbles. This will result in a major step forward and a valuable tool in designing engineering solutions and ocean and climate modeling. The award will also support educational activities for elementary school students, undergraduates, and graduate students. Software developed through this work will be open source and widely available to the public and other researchers interested in modeling multiphase flows.This work will develop an understanding of the multi-scale nature of bubble break-up phenomena under realistic conditions in terms of turbulent flow and the physico-chemical complexity of the interfaces. The break-up of bubbles far from the critical break-up size exhibits dramatic behavior, with the formation of multiple tiny satellite bubbles. The presence of surfactants at the bubble interface, ubiquitous in nature and industry, lowers the interfacial tension and affects the break-up processes. However, this latter aspect remains largely unexplored. Systematic experiments and direct numerical simulations for various turbulence configurations will probe these multi-scale regimes. The researchers will also characterize experimentally the role of the physico-chemical properties of the interface by working with controlled surfactant and salinity conditions. In the absence of surfactant, researchers will determine how the break-up dynamics and child bubble statistics are controlled by the ratio between the bubble size and the turbulent Taylor microscale, which controls the excitation range scale, and the ratio between the bubble size and the critical Hinze scale, which controls the break-up mode and the local or non-local range of child bubble size production. In the presence of surfactants, researchers will characterize the filamentary structures that arise due to the extended stability of interfaces, leading to the generation of much smaller bubble fragments. From these extensive data sets, a mathematical framework that can be implemented in multi-phase simulations of the Navier-Stokes equations will be developed. This will allow the modeling of fragmentation in turbulent flow with complex surface rheology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.