Collaborative Research: Coupled Numerical and Laboratory Investigations of Chaotic Advection to Enhance Spreading and Reaction in Three-Dimensional, Heterogeneous Porous Media

修复受污染地下水的一种方法是引入一种化学溶液，该溶液将与污染物发生反应并降解污染物。如果引入的化学溶液扩散到整个受污染地区，这种补救方法是最成功的。地下水流经的多孔材料自然是非均质的，这意味着水更容易流经某些部分，而不容易流经其他部分。这种不均一性自然会导致化学溶液向受污染的地下水扩散，即所谓的被动扩散。额外的扩散，称为主动扩散，可以通过在受污染地区诱导某些时变的地下水流动模式来发生。某些时变流动被归类为混沌平流，已知可显著增强主动扩散。被动扩散和主动扩散都会促进污染物的降解；然而，主动扩散和被动扩散的综合影响还不是很清楚。在这个项目中，将使用一套实验室实验和数值模拟(1)研究被动扩展和主动扩展之间的相互作用以及各自在促进退化方面所起的作用，以及(2)开发针对不同非均质性模式设计混沌平流模式的策略。实验室实验将使用新的基于激光的光学技术，以可视化和量化被动和主动扩散对污染物降解的综合影响。修复受污染的地下水、开采地热能和某些类型的金属开采等活动都依赖于化学溶液在多孔地质材料中的扩散。由于地质材料的天然非均质性，了解非均质性与混沌平流之间的关系及其对传播的影响是这些应用成功的关键。该项目还将开发新的实验室技术，可以在测量多孔介质中的反应传输方面取得突破。

One method for remediating contaminated groundwater is to introduce a chemical solution that will react with and degrade the contaminant. This remediation method is most successful if the introduced chemical solution is spread throughout the contaminated area. The porous materials through which groundwater flows are naturally heterogeneous, meaning that water flows more easily through some parts and less easily through others. This heterogeneity naturally causes some spreading, called passive spreading, of the chemical solution into the contaminated groundwater. Additional spreading, called active spreading, can occur by inducing certain time-varying patterns of groundwater flow in the contaminated area. Certain time-varying flows, classified as chaotic advection, are known to substantially enhance active spreading. Both passive and active spreading lead to enhanced degradation of the contaminant; however, the combined effect of active and passive spreading is not well understood. In this project, a suite of laboratory experiments and numerical simulations will be used (1) to investigate the interplay between passive and active spreading and the role that each plays in enhancing degradation, and (2) to develop strategies for designing chaotic advection patterns for different patterns of heterogeneity. The laboratory experiments will be conducted using novel laser-based optical techniques to visualize and quantify the combined effects of passive and active spreading on contaminant degradation. Activities such as remediation of contaminated groundwater, extraction of geothermal energy, and certain types of mining of metals all rely on spreading of chemical solutions in porous geological materials. Because of the natural heterogeneity of geological materials, an understanding of the relationship between heterogeneity and chaotic advection and their effects on spreading is critical to the success of these applications. This project will also develop new laboratory techniques that could provide a breakthrough in measurement of reactive transport in porous media.