CAREER: Bubble fragmentation in turbulent flows

在许多环境和工业情况下，湍流中气泡的破碎是重要的。 这些措施包括减少石油泄漏，船舶和潜艇中船首波浪夹带的空气，以及与破碎波相关的海洋-大气相互作用。 气泡界面在湍流作用下会发生剧烈的变形和破裂，新形成的界面极大地促进了气液两相之间的传热传质。 该奖项描述了一系列最先进的数值和实验研究的破碎气泡在湍流。我们的目标是产生一个通用的模型，描述的湍流和界面特性的气泡破裂的作用。 这将是一个重大的进步，也是设计工程解决方案以及海洋和气候建模的宝贵工具。 该奖项还将支持小学生、本科生和研究生的教育活动。 通过这项工作开发的软件将是开源的，并广泛提供给公众和其他研究人员有兴趣在模拟多相流。这项工作将开发的多尺度性质的气泡破碎现象在湍流和界面的物理化学复杂性方面的现实条件下的理解。远离临界破裂尺寸的气泡的破裂表现出戏剧性的行为，形成多个微小的卫星气泡。在自然界和工业中普遍存在的气泡界面处的表面活性剂的存在降低了界面张力并影响破裂过程。 然而，后一个方面在很大程度上仍未得到探索。系统的实验和直接数值模拟各种湍流配置将探测这些多尺度制度。研究人员还将通过控制表面活性剂和盐度条件来实验表征界面的物理化学性质的作用。在没有表面活性剂的情况下，研究人员将确定破裂动力学和子气泡统计数据如何由气泡尺寸和湍流泰勒微尺度之间的比率控制，该比率控制激发范围尺度，以及气泡尺寸和临界欣泽尺度之间的比率，该比率控制破裂模式和子气泡尺寸生产的局部或非局部范围。在表面活性剂的存在下，研究人员将表征由于界面的扩展稳定性而产生的结构，从而产生小得多的气泡碎片。从这些广泛的数据集，一个数学框架，可以在多相模拟的纳维尔-斯托克斯方程的实施将开发。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.