CAREER: Gas-Liquid Interface Dynamics and Dissipation Mechanisms in Capillary-Scale Two-Phase Flow

大规模系统中的两相流在历史上对流体力学和传热学领域非常重要。MEMS分析装置、微尺度热交换器、天基处理和热控制技术以及燃料电池等陆基技术的进展突出表明，需要更好地理解具有强毛细管成分的气液流动。由于不能正确地考虑毛细力、由于微流体运动引起的耗散和气液界面相互作用的影响，开发用于小尺度系统的通用流型图的尝试一直是不成功的。PI将对毛细管尺度的两相流进行系统的实验和分析研究，并开发工程设计工具。大学预科，本科和研究生的教育机会是整个研究计划的整合。前三个重叠的研究阶段包括定性实验，研究气液界面动力学和发展的高速共聚焦显微镜技术。该计划的第二阶段侧重于利用高速共聚焦显微镜技术进行动态气液界面附近的微粒子图像测速（micro-PIV）的定量研究;目前任何可用的micro-PIV方法都无法访问的流动区域。 第二阶段的分析和实验研究将隔离和量化的影响，表面张力，界面曲率，界面剪切，气相惯性和压缩性，流体动力学耗散由于微通道运动和动态接触线的形态上的两相流通过微通道。所有这些效应都在毛细管尺度的两相流中观察到，但没有量化。第三阶段将构建和测试用于设计和开发先进技术的预测工具，并改进水管理策略，以实现更可靠的燃料电池运行。 研究结果将有助于开发汽车燃料电池，其中无法有效管理氢氧反应产生的水是大规模部署的主要困难之一。这项研究的影响有教育方面和社会方面。研究生和本科生培训是这项工作的重要组成部分。学生将通过现有的密歇根理工大学教育合作伙伴关系从代表性不足的群体中招募。这项研究的教育方面的一个关键因素是研究生到本科生和本科生到大学预科生的分层指导，学生通过演示和其他学生的指导学习。社会影响将在先进技术的发展中最为明显，特别是在燃料电池等替代能源转换技术方面。这项研究的结果将是一个更彻底的，定量的了解系统中的两相流，其中毛细作用力是重要的，这种理解的应用，以推进技术，同时培养学生的人才在不断增长的领域的微型设备和燃料电池。

CBET-0748049AllenTwo-phase flow in large-scale systems has historically been important to the fields of hydrodynamics and heat transfer. Advances in MEMS analytical devices, microscale heat exchangers, space-based processing and thermal control technologies, and terrestrial-based technologies such as fuel cells have highlighted the need for improved understanding of gas-liquid flow with a strong capillary component. Attempts at developing universal flow regime maps for small scale systems have been unsuccessful due to the inability to properly account for the effects of capillary forces, dissipation due to menisci motion and gas-liquid interface interaction. The PI will conduct a systematic experimental and analytical investigation of two-phase flow at the capillary scale and develop engineering design tools. Educational opportunities for pre-college, undergraduate and graduate students are integrated throughout the research program. The first three overlapping research phases consists of qualitative experiments to study gas-liquid interface dynamics and development of a high-speed confocal microscopy technique. The second phase of this program focuses on quantitative studies utilizing the high-speed confocal microscopy technique for micro-Particle Image Velocimetry (micro-PIV) near dynamic gas-liquid interfaces; a region of flow not accessible with any currently available micro-PIV methods. The analytical and experimental studies of the second phase will isolate and quantify the effects of surface tension, interface curvature, interface shear, gas phase inertia and compressibility, hydrodynamic dissipation due to menisci motion and dynamic contact lines on the morphology of the two-phase flow through microchannels. All of these effects have been observed in capillary-scale two-phase flow, but not quantified. The third phase will construct and test predictive tools for design and development of advanced technologies and to improve water management strategies for more reliable fuel cell operation. The results of research will help in development of automotive fuel cells where inability to effectively manage the water produced by the hydrogen-oxygen reaction constitutes one of the major difficulties in mass deployment. Impacts of this research have an educational aspect and a societal aspect. Graduate and undergraduate student training is an important part of this work. Students will be recruited from under-represented groups through existing Michigan Tech educational partnerships. A key element of the educational aspect of this study is the tiered mentoring of graduate to undergraduate students and undergraduate to pre-college students where students learn through demonstration and instruction from other students. The societal impact will be most evident in advanced technology development; particularly with respect to alternative energy conversion technologies such as fuel cells. The results of this study will be a more thorough, quantitative understanding of two-phase flow in systems where capillary forces are important and application of this understanding to advance technology while developing student talent in the growing field of microscale devices and fuel cells.