CAREER: Revisiting Two Basic Processes in Hydrogeology -- Solute Transport in Heterogeneous Formations and Chemical Mixing in Porous Media

职业：重新审视水文地质学中的两个基本过程——非均质地层中的溶质迁移和多孔介质中的化学混合

• 批准号: 9875995
• 负责人: Charles Harvey
• 金额: $ 27.04万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2004-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9875995&HistoricalAwards=false
• 关键词: CAREER; Revisiting; Two; Basic; Processes

9875995HarveyThe proposed research will reconsider two basic processes in hydrogeology: Solute transport through formations with heterogeneous hydraulic conductivity, and chemical mixing and reaction in porous media. The educational initiative will consist of building new classroom tools that combine physical models with numerical simulation, and developing projects that integrate graduate education with local hydrogeologic issues.When does spatially variable hydraulic conductivty cause dispersion and when does it cause nonequilibrium mass transfer? Hydrogeologists and soil scientists have found that spatial heterogeneity in permeability strongly influences the transport of solutes in groundwater. Researchers are divided between two principal schools of thought. The first models the effects of heterogeneity as a mass-transfer (or dual-porosity) process, and parameterizes the size of immobile zones. The second models the effects based on heterogeneity on transport as a dispersive, usually Fickian, process and relates an effective (or macro) dispersion coefficient to the spatial statistics of the permeability field. We will conduct experimental and theoretical research to determine the conditions under which each model is appropriate. In particular, we will investigate the type of spatial structures that give rise to diffusive mass transfer.How do chemicals mix and react to porous media? Developing accurate models of reaction in porous media hinges on accounting for the way molecules meet each other before they can react, and mechanical dispersion and chemical mixing (or pore-scale mixing) may not be synonymous. For example, mechanical dispersion may result, in part, from solute movement through some pores, but not through adjacent pores.Combining physical demonstrations and numerical modeling. Students gain understanding of the connection (and differences) between natural processes and mathematical models by using physical models simultaneously with numerical models in the classroom. The combination gives students insight into the relation of conceptual/mathematical models and physical reality. The two will be joined by using an LCD projector to display the visual output of a numerical transport simulation directly onto a demonstration tank, superimposing the simulated and real dye plumes. Integrating hydrogeology and policy. Students will be engaged in local hydrologic issues by involvement in a nonprofit organization that provides environmental and hydrologic expertise for local communities.

这项拟议的研究将重新考虑水文地质学中的两个基本过程：溶质在具有非均匀水力传导性的地层中的传输，以及在多孔介质中的化学混合和反应。这项教育计划将包括建立新的课堂工具，将物理模型与数值模拟相结合，并开发将研究生教育与当地水文地质问题相结合的项目。空间可变的水力传导性何时会导致弥散，何时会导致非平衡传质？水文地质学家和土壤学家发现，渗透率的空间非均质性强烈影响地下水中的溶质运移。研究人员分为两个主要的思想流派。第一种模型将非均质性的影响模拟为传质(或双重孔隙度)过程，并对不动区域的大小进行了参数化。第二种是将基于非均质性对运移的影响模拟为色散的，通常是费克过程，并将有效(或宏观)弥散系数与渗透率场的空间统计联系起来。我们将进行实验和理论研究，以确定每种模式适用的条件。特别是，我们将研究引起扩散传质的空间结构类型。化学物质如何与多孔介质混合和反应？在多孔介质中开发准确的反应模型取决于考虑分子在反应之前彼此相遇的方式，而机械分散和化学混合(或孔尺度混合)可能不是同义词。例如，机械弥散可能部分是由于溶质通过一些孔隙的运动造成的，而不是通过相邻的孔隙。学生通过在课堂上同时使用物理模型和数值模型来理解自然过程和数学模型之间的联系(和区别)。这种结合让学生深入了解概念/数学模型与物理现实之间的关系。两者将通过使用LCD投影仪将数值运输模拟的视觉输出直接显示在演示坦克上，将模拟的染料羽流和真实的染料羽流叠加在一起。将水文地质与政策相结合。学生将通过参与一个为当地社区提供环境和水文专业知识的非营利性组织来参与当地的水文问题。