Collaborative Research: Upscaled Mass Transfer Coefficients for Modeling Dissolution of Nonaqueous Phase Liquids in Homogeneous and Heterogeneous Porous Media in the Field

[04:40 . 21]米勒非水相液体（NAPLs）的地下污染是经常发生的。影响napl污染场地风险评估和环境管理决策的最重要过程之一是napl溶解到地下水中的速度。NAPL溶解控制着污染物向下梯度受体的通量，是影响监测系统设计、人类和生态风险评估以及修复策略选择的重要过程。智力优点：NAPL溶解的许多模型已经开发基于并打算描述厘米级实验室柱。虽然我们对这一尺度的NAPL溶解的理解相对成熟，但这种理解并不能转化为可靠的场尺度模型，原因有两个：(1)如果试图解决已知对场尺度模拟很重要的厘米尺度特征，当前技术的计算问题是棘手的；(2)在计算上易于处理的NAPL溶蚀升级模型尚处于发展初期。我们在之前的工作中已经表明，溶解过程导致溶解指的形成，这对溶解速度有深远的影响。因为在某些情况下，这些手指可以影响两个或两个以上数量级的传质速率，所以必须在场尺度模拟器中表示这种机制的影响，我们知道没有这样做过的情况。这项工作的目标是扩展一种新的基于分形的上尺度方法，以产生一个非线性的、多尺度的传质模型，适用于更现实的场尺度模拟。多尺度模型是地下科学的圣杯，实际上是大多数科学的圣杯。迄今为止，我们在这方面的努力取得了相当大的成功，但影响NAPL溶解指法的几个关键尚未解决的问题仍然存在：NAPL润湿性，多孔介质非均质性，溶解开始时NAPL污染的初始空间分布，以及实际的场尺度非均质性模式对手指和NAPL溶解的发展和演变的影响。创造性的理论，新颖的实验和先进的计算方法的结合将被用来解决这些问题。更广泛的影响：在这项工作中，将开发一个数值模型并用于研究非线性过程，并将条件范围扩展到可以在实验室中轻松研究的条件范围，扩展到那些典型的复杂自然系统。实验和计算方法之间的协同作用提供了一个独特的机会，吸引高中和本科工程和科学学生进入地下水文学和计算科学的令人兴奋的世界。为此，我们将根据我们的工作创建两个基于问题的学习（PBL）模块，这些模块将在特拉华大学（UD）和北卡罗来纳大学（UNC）的本科生中进行测试，并用于一个旨在吸引有天赋的高中生进入工程和科学领域的项目。PBL是以学生为中心或主动学习的成功范例，其优势已被教育心理学的研究牢牢确立。特拉华大学已经将PBL作为一个机构重点，并已成为国内和国际PBL的领导者，他们将把这些PBL教育模块传播给美国各地的教师。此外，这项研究将直接涉及来自活跃的研究小组的本科生和研究生，这些研究小组对科学和工程领域的代表性不足的群体既有强烈的承诺，也有代表性

0440211MillerSubsurface contamination by nonaqueous phase liquids (NAPLs) is a frequent occurrence. One of the most important process influencing risk assessment and environmental management decisions at NAPLcontaminated sites is the rate at which NAPLs dissolve into groundwater. NAPL dissolution controls fluxes of contaminants to down-gradient receptors, and is a significant process affecting the design of monitoring systems, the assessment of human and ecological risk, and the selection of remediation strategies.Intellectual Merit: Numerous models for NAPL dissolution have been developed based upon and intended to describe centimeter-scale laboratory columns. While our understanding of NAPL dissolution at this scale is relatively mature, this understanding does not translate to reliable field-scale models for two reasons: (1) the computational problem is intractable with current technology if one endeavors to resolve centimeter-scale features known to be important for field-scale simulations; and (2) upscaled models of NAPL dissolution, which are computationally tractable, are in their developmental infancy. We have shown in previous work that the dissolution process leads to the formation of dissolution fingers, which have aprofound effect on the rate of dissolution. Because these fingers can affect the rate of mass transfer by two or more orders of magnitude in some cases, it is essential that the effect of this mechanism be represented in field-scale simulators, and we know of no case in which this has been done.The goal of this proposed work is to extend a novel fractal-based upscaling approach to produce a nonlinear, multiscale mass transfer model suitable for more realistic field-scale simulation. Multiscale models are the holy grail of subsurface science, indeed much of science in general. Our efforts to date in this regard have met with considerable success, but several key unresolved issues that influence NAPL dissolution fingering remain: NAPL wettability, porous medium heterogeneity, the initial spatial distribution of NAPL contamination at the onset of dissolution, and the effect of realistic patterns of field-scale heterogeneity on the development and evolution of fingers and NAPL dissolution in general. A combination of creative theoretical, novel experimental, and advanced computational approaches will be used to address these issues.Broader Impacts: In this work, a numerical model will be developed and used to investigate a nonlinear process and to extend the range of conditions beyond what can be easily studied in the laboratory to those typical of complex natural systems. The synergy between the experimental and computational approaches provides a unique opportunity to draw high school and undergraduate engineering and science students into the exciting world of subsurface hydrology and computational science. To that end, we will create two Problem-Based Learning (PBL) modules based on our work that will be tested with undergraduate students at the University of Delaware (UD) and the University of North Carolina (UNC) and used in a programintended to attract gifted high school students into engineering and science. PBL is a successful example of student-centered or active learning, the strengths of which have been firmly established by research in educational psychology. UD has developed an institutional focus on PBL and has become a national and international PBL leader, and they will disseminate these PBL educational modules to instructors throughout the US. In addition, this research will involve directly both undergraduate and graduate students from active research groups that have both a strong commitment to and representation of under-represented groups in science and engineering.1