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

国际研究奖学金计划使美国科学家和工程师能够在国外进行三到二十四个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持Woodrow L.Shew博士与法国里昂高等高等学院Jean-Francois Pinton博士为期17个月的研究奖学金。气液流动在各种医疗、工业和自然环境中发挥着关键作用。在医学环境中，气泡被认为可以增强超声成像，并显示出在受控药物输送和基因转染方面的前景。湍流海浪中的空气夹带对于碳封存和海洋生态系统的健康至关重要。沸腾换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。气泡对船舶的流体动力学和油气管道中的两相流动都有影响。尽管大量的应用将会受益，但我们对气泡如何与复杂的流体流动相互作用的理解存在重大差距。一种独特的三维超声技术提供了对三种流动序列中气泡行为的观察：均匀旋转的层流、湍流涡流和充分发展的湍流。在每一种情况下，鲜为人知的升力和历史效应都会影响气泡的运动。当流动中存在涡量时，升力起作用，历史效应是由于气泡与其自身尾迹的相互作用。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。将小尺度行为与大尺度行为联系起来是本研究的主要目的，对实际应用中的气泡流动进行准确的建模和预测是必要的。

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.