Viscosity-driven Enhanced Hydrological Connectivity

受污染的地下水资源的补救或清理是一个众所周知的社会问题，需要更好地了解含水层中的水与化学品如何混合，从而找到更有效的解决方案。许多造成污染或用作去污补救剂的化学品具有与水不同的粘度和密度。这些差异导致复杂的流动模式，特别是在具有异质水力特性的含水层中，因为一种流体在天然地下水流动或用于地下水净化的泵送和处理操作期间被另一种流体推动。粘性指进就是这种复杂流动模式的一个例子，当粘性较低的化学品或水推动粘性较高的水或化学品通过含水层时，就会形成这种流动模式。在两种流体之间的边界处自发形成的指状物控制污染或去污扩散的速度和距离。本项目的目标是了解和预测粘性指状物的增长以及在污染/补救区域内的相关扩散和混合。粘性指进的实验室实验和数值模拟将进行一系列的流体粘度对比和含水层的非均质性代表美国含水层，以产生数据，测试污染物/补救流体的扩散和混合的假设。拟议的研究特别适用于遭受加油站地下储罐燃料泄漏的特大城市，因为汽油添加剂和水之间的粘度差异。该项目还计划开展教育活动，让本科生和研究生通过动手的数值和物理建模工具学习地下水污染和补救的机制。这个项目将提高我们目前的了解如何溶质羽流的物理性质与渗透率的异质性相互作用，影响羽流的扩散和混合在流体动力学不稳定的运输过程中，通过强烈的非均质岩石。由于不同类型的有机/无机污染物的物理性质的可变性，需要这种理解来预测和控制污染物的补救和去除过程。基于高分辨率的数值模拟，流体动力学弥散和不稳定性的理论，和新的实验的溶质在固结岩石中的传输，渗透率的非均匀性和粘度差异之间的相互作用和控制的混合和扩散的溶质羽将被量化。通过评估新的度量定义的突破曲线和拓扑结构的控制平面浓度图，这是现场可观测的，将被量化的贡献的粘度对比度的溶质到达时间和混合区长度的羽流连通性。了解如何粘度对比，在异质性的存在下，影响溶质的连通性和运输是高度相关的含水层修复，风险分析，地下废物处理和化学工业。本科生和研究生将接受Hele-Shaw细胞实验的培训，建立污染和补救的物理含水层模型，并组织粘性指状艺术展。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Remediation or cleanup of contaminated groundwater resources is a well-known societal problem for which more effective solutions that are based on a better understanding of how water mixes with chemicals in aquifers is required. Many chemicals that are either responsible for contamination or used as a remedial agent for decontamination have viscosities and densities different from water. These differences lead to complex flow patterns, especially in aquifers with heterogeneous hydraulic properties, as one fluid is pushed by the other during natural groundwater flow or pump-and-treat operations for groundwater cleanup. Viscous fingering is an example of such a complex flow pattern that develops when a less viscous chemical or water pushes a more viscous water or chemical through the aquifer. The fingers that form spontaneously at the boundary between the two fluids control how fast and how far the contamination or decontamination spreads. Understanding and predicting the growth of viscous fingers and the associated spreading and mixing within contaminated/remediated regions is the goal of this project. Lab experiments and numerical simulations of viscous fingering will be conducted for a range of fluid viscosity contrasts and aquifer heterogeneities representative of U.S. aquifers to generate data for testing hypotheses on spreading and mixing of contaminant/remedial fluids. The proposed research is particularly relevant to megacities suffering from fuel leakage from underground storage tanks at gas stations because of the viscosity contrast between gasoline additives and water. Educational activities that involve undergraduate and graduate students in learning the mechanisms of groundwater contamination and remediation through hands-on numerical and physical modeling tools are also planned in this project. This project will improve our current understanding of how the physical properties of a solute plume interact with permeability heterogeneity to affect plume spreading and mixing during hydrodynamically unstable transport through strongly heterogeneous rocks. This understanding is required to predict and control contaminant remediation and removal processes because of the variability in the physical properties of different types of organic/inorganic contaminants. Based on high-resolution numerical simulations, theory of hydrodynamic dispersion and instability, and novel experiments of solute transport in consolidated rocks, the interplay between permeability heterogeneity and viscosity contrast and its control on mixing and spreading of a solute plume will be quantified. By evaluating new metrics of plume connectivity that are defined in terms of the breakthrough curve and the topology of the control plane concentration map, which are field observables, the contribution of the viscosity contrast to the solute arrival time and the mixing zone length will be quantified. Understanding how viscosity contrasts, in the presence of heterogeneity, impacts solute connectivity and transport is highly relevant for aquifer remediation, risk analysis, underground waste disposal, and the chemical industry. Undergraduate and graduate students will be trained in conducting Hele-Shaw cell experiments, building physical aquifer models of contamination and remediation, and organizing a viscous fingering art exhibition.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.