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

合作研究：用于模拟现场均质和非均质多孔介质中非水相液体溶解的放大传质系数

• 批准号: 0440236
• 负责人: Paul Imhoff
• 金额: $ 19.39万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-01-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440236&HistoricalAwards=false
• 关键词: Collaborative; Research; Upscaled; Mass; Transfer

0440236ImhoffSubsurface 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

0440236 Imhoff非水相液体（NAPL）造成的地下污染经常发生。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在地下水中的溶解速率。NAPL溶解控制污染物通量下降梯度受体，是一个重要的过程，影响监测系统的设计，人类和生态风险的评估，以及选择的补救strategies.Intellectual Merit：NAPL溶解的许多模型已经开发的基础上，并打算描述厘米级的实验室列。虽然我们对NAPL溶解的理解在这个尺度上是相对成熟的，但这种理解并没有转化为可靠的场尺度模型，原因有两个：（1）如果努力解决已知对场尺度模拟重要的厘米尺度特征，则计算问题在当前技术下是棘手的;（2）NAPL溶解的放大模型，这是计算上容易处理的，是在他们的发展初期。我们在以前的工作中已经表明，溶解过程导致溶解指的形成，这对溶解速率有深远的影响。由于这些手指可以影响传质速率的两个或更多的数量级，在某些情况下，这是必要的，这种机制的影响表示在现场规模的模拟器，我们知道没有这样做的情况下，这项工作的目标是扩展一种新的分形为基础的放大方法，以产生一个非线性，多尺度传质模型适用于更现实的现场规模的模拟。多尺度模型是地下科学的圣杯，实际上是一般科学的圣杯。我们迄今为止在这方面的努力已经取得了相当大的成功，但仍然存在几个关键的未解决的问题，影响非水相液体溶解指：非水相液体润湿性，多孔介质的异质性，初始空间分布的非水相液体污染在开始溶解，和现实模式的影响，现场规模的异质性的发展和演变的手指和非水相液体溶解一般。创造性的理论，新颖的实验和先进的计算方法相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，并用于调查一个非线性过程，并扩大范围的条件超出了什么可以很容易地在实验室研究那些典型的复杂的自然系统。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州大学（UD）和北卡罗来纳州大学（北卡罗来纳州）的本科生中进行测试，并用于吸引有天赋的高中生进入工程和科学领域。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所确立。UD已经发展了对PBL的机构重点，并已成为国家和国际PBL的领导者，他们将传播这些PBL教育模块，以教师在美国各地。此外，这项研究将直接涉及来自活跃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代表性不足的群体有着强烈的承诺和代表性。