International Research Fellowship Program: Effects of Lift Forces and Turbulence on Bubble Motion

[401986 . 06]国际研究奖学金计划使美国科学家和工程师能够到国外进行3至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持伍德罗·l·肖（Woodrow L. show）博士与让-弗朗索瓦·平顿（Jean-Francois Pinton）博士在法国里昂高等师范学院开展为期17个月的研究。气液流动在各种医疗、工业和自然环境中发挥着至关重要的作用。在医疗环境中，已知气泡可以增强超声成像，并显示出控制药物输送和基因转染的希望。湍流海浪中的空气夹带对碳固存和海洋生态系统的健康至关重要。沸腾传热和许多化学反应的效率取决于气泡的分布和与流体的相互作用。气泡影响船舶的流体力学和油气管道中的两相流。尽管大量的应用将从中受益，但我们对气泡如何与复杂流体流动相互作用的理解仍有很大的差距。一种独特的三维超声技术提供了三种流动序列中的气泡行为观察：均匀旋转层流，湍流涡旋和完全发展的湍流。在每一种情况下，人们对升力和历史效应的理解都很差，它们会影响气泡的运动。当气流中存在涡度时，升力起作用，而历史效应是由于气泡与其自身尾迹的相互作用造成的。我们研究了这些对单个气泡的影响，以及它们如何在许多气泡的大规模集体行为中表现出来。连接小尺度和大尺度的行为是本研究的首要目标，也是在实际应用中准确建模和预测气泡流动的必要条件。

0401986ShewThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a seventeen-month research fellowship by Dr. Woodrow L. Shew to work with Dr. Jean-Francois Pinton at Ecole Normale Superieure de Lyon in France.Gas-liquid flows play a crucial role in a diverse range of medical, industrial, and natural settings. In the medical setting, bubbles are known to enhance ultrasound imaging and show promise for controlled drug delivery and gene transfection. Air entrainment in turbulent ocean waves is critical for carbon sequestering and for the health of ocean ecosystems. Efficiency of boiling heat transfer and many chemical reactions depend upon bubble distribution and interaction with the fluid. Bubbles affect the hydrodynamics of ships and two-phase flow in gas/oil pipelines. Despite the large number of applications that would benefit, our understanding of how bubbles interact with complex fluid flows has significant gaps. A unique three-dimensional ultrasound technique provides observations of bubble behavior in a sequence of three flows: uniformly rotating laminar flow, a turbulent vortex, and fully developed turbulence. In each of these cases, the poorly understood lift forces and history effects influence the motion of the bubble. The lift force plays a role when vorticity is present in the flow and the history effects are due to interactions of the bubble with it's own wake. We study these effects on individual bubbles as well how they manifest in large-scale collective behavior of many bubbles. Connecting the small and large-scale behaviors is the primary goal of this research and is necessary to accurately model and predict bubbly flows in practical applications.