CAREER: Interfacial Behavior of Microbubbles During Contaminant Stripping in Saturated Soils: Multiscale Investigations in Research and Education

9984206-燃烧这一学院早期职业发展(职业生涯)研究和教育项目致力于研究控制离散气泡在饱和土壤中形成和移动的物理因素。在地质环境应用中，注入气泡的传输和分布对空气喷射过程的有效性至关重要。空气喷射过程是一种原位剥离技术，旨在将挥发性有机化合物转移到气相中。该项目对气泡在孔隙、孔隙网络和连续尺度土壤模型中的传输动力学进行了多尺度的实验研究。空气传输的速率和模式被量化为模型土壤孔隙中的注入压力/速度、注入孔口和界面张力的函数。采用蚀刻玻璃微观模型来模拟土壤孔隙网络中的空气运移，并将空气饱和度、气泡体积和运移非均质性作为在孔隙尺度上确定的控制参数的函数来量化。微观尺度的研究操纵系统参数，如注射速度和界面张力，以确定导致气泡直径减小、气泡停留时间增加和气泡表面积增加的条件。剥离具有这些特征的气泡大大增强了全球范围内的空气喷发过程。在孔隙和孔隙网络尺度上获得的数据被用作在连续介质尺度上执行的柱试验的输入。柱试验根据在孔隙和孔隙网络尺度研究中确定的增强型系统控制参数来量化污染物去除效率、气泡合并程度和传质效果。在这项多尺度调查中获得的数据将通过发展对控制气泡在其他饱和土壤系统中运动的变量的严格的、基本的理解而显著提高知识的状态。虽然提出的目标是在空气喷雾的框架内设定的，但多尺度基础调查的结果同样适用于类似的过程，如石油开采。与研究项目的发展平行，微尺度物理和化学现象的影响交织在本科土木工程课程、本科研究和旨在吸引中学女生攻读理工科专业的研讨会中。将多尺度物理化学行为的考虑融入课堂讲课和一系列五分钟的课堂演示实验中。这些“变化”实验是精心设计的，用来说明工程实践中微观现象的宏观效应。正在开发一门本科生补救案例研究课程，该课程将微尺度的物理和化学考虑纳入补救设计。此外，正在开发和实施一个旨在鼓励中学女生学习科学和工程的外联讲习班。

9984206- BurnsThis Faculty Early Career Development (CAREER) research and education project addresses the physical factors that govern the formation and movement of discrete air bubbles through otherwise saturated soils. In geoenvironmental applications, the transport and distribution of injected air bubbles is critical to the effectiveness of the air sparging process -- an in-situ stripping technique designed to mobilize volatile organic compounds to the vapor phase. The project involves an experimental, multi-scale investigation into the dynamics of air bubble transport through pore, pore network, and continuum scale soil models.The rate and pattern of air transport is quantified as a function of injection pressure/velocity, injection orifice, and interfacial tension in a model soil pore. Etched glass micromodels are used to simulate air transport through soil pore networks, and the air saturation, bubble volume, and transport heterogeneity are quantified as a function of the controlling parameters identified at the pore scale. The microscale investigations manipulates the system parameters, such as injection velocity and interfacial tension, in order to identify the conditions that lead to decreased bubble diameter, increased bubble residence time, and increased bubble surface area. Stripping bubbles with these characteristics significantly enhances the air sparging process at the global scale. The data obtained at the pore and pore network scales is used as inputs for column tests performed at the continuum scale. The column tests quantifies contaminant removal efficiency, degree of bubble coalescence, and mass transfer effects, based on the enhanced system control parameters identified in the pore and pore network scale investigations.The data obtained in this multiscale investigation will significantly enhance the state of knowledge by developing a rigorous, fundamental understanding of the variables that control bubble movement through otherwise saturated soil systems. While the objectives proposed are set within the framework of air sparging, the results of the multiscale, fundamental investigation are equally applicable to similar processes, such as petroleum recovery.Parallel to the developments in the research project, the influence of microscale physical and chemical phenomena is interwoven into undergraduate Civil Engineering courses, undergraduate research, and a workshop targeted to attract middle school girls to pursue the study of science and engineering. Consideration of multiscale physical and chemical behavior is integrated into classroom lectures and a series of five-minute classroom demonstration experiments. These "change-up" experiments are carefully designed to illustrate the macroscale effects of microscale phenomena in engineering practice. An undergraduate remediation case studies course that incorporates microscale physical and chemical considerations into remedial design is being developed. Additionally, an outreach workshop designed to encourage middle school girls in the study of science and engineering is being developed and implemented.