Exploratory Investigation of Thermally-Induced Water Flow in Soils

该项目旨在回答一个非常基本但非常古老的科学问题：“由于多孔材料的温度梯度，水为什么以及如何移动？”这种热诱导的水通量普遍存在于多孔材料中，无论何时都存在传热和水运动。对这一现象的科学理解是应对许多重要科学和社会挑战的必要基础：气候对地质材料的影响、地热能应用、极端条件下多孔材料的行为，以及非常规化石燃料（如天然气水合物和页岩气）的开采。然而，尽管具有重要意义，但这一现象一直是一个历史上未解决的和令人困惑的问题，影响了许多科学和工程领域，从土木工程、土壤科学和石油工程等传统应用到微流体、材料加工和生物力学等新兴需求。该奖项支持探索新的研究概念/方法及其应用，以揭示热诱导水通量的物理机制，为这一现象提供完整的科学描述和分析框架。作为一项探索性研究，它开创了一个高风险但可能高回报的概念，研究的成功可能为岩土学界解决许多在现有框架中难以解决的问题提供新的认识，也为目前分散在各个学科的多孔材料研究提供了一种整合方法。除了支持一名博士生外，该项目还将支持密歇根州上半岛农村、低社会经济水平学生和土著部落社区的推广活动。将建立一个年度暑期项目，让K-12学生参与动手学习，以了解多孔材料。该项目将采用一种新的概念/方法，即多尺度驱动的多物理场，来解决现有方法难以解决的问题。研究将首先关注热诱导水通量的宏观机制。为此，通过进行两个子任务，将热诱导水通量与接触角的温度依赖关系联系起来：用新设计的研究装置测量热诱导水通量；用改进的毛细管上升法测量接触角。然后进行分子动力学分析，揭示接触角温度依赖下的微观机制，假设接触角的温度依赖归因于蒸汽吸附的温度依赖。最后，将测量吸附等温线，以实验验证假设，并在宏观和微观尺度上耦合框架，旨在建立一个基于物理和实际可实施的热诱导水通量框架。这项研究可能非常重要，因为它试图通过理论创新（宏观和微观尺度的新理论）、实验（接触角和热诱导通量测量）和数值方面（水-矿物系统的分子模拟）取得突破。从长远来看，该项目也是一项探索性的努力，旨在研究多尺度驱动的多物理场概念，以便解决关键的历史问题和即将在可持续性，能源和环境保护方面的应用中出现的紧迫挑战，这些问题越来越多地涉及土壤的非等温行为，从广义上讲，多孔材料中的多物理场。

This project aims to answer a very fundamental yet very old scientific question: "Why and how does water move due to temperature gradients in porous materials?" This thermally induced water flux ubiquitously exists in porous materials, whenever both heat transfer and water movement are present. A scientific understanding of this phenomenon is an essential base for many important scientific and social challenges: climate effects on geomaterials, geothermal energy applications, behavior of porous materials under extreme conditions, and recovery of non-conventional fossil fuels such as gas hydrates and shale gas. However, despite the significance, this phenomenon has been an historically unsolved and perplexing issue affecting many science and engineering areas involving porous materials from traditional applications in civil engineering, soil science and petroleum engineering to emerging needs in microfluidics, material processing and biomechanics. This award supports the exploration of a new research concept/methodology and its application to reveal the physical mechanisms underlying thermally induced water flux for a complete scientific description and analysis framework for this phenomenon. As an exploratory study, which pioneers a very high-risk but possibly high-return concept, the success of the study may provide the geotechnical community a new understanding to tackle many issues which are hard to solve in the existing frameworks, and also provide a way to integrate porous material research which is currently distributed in various disciplines. In addition to supporting a doctoral student, the project will support outreach activities for rural, low-socioeconomic students and native tribal communities in the Upper Peninsula of Michigan. An annual summer program will be established to engage K-12 students in hands-on-learning for understanding of porous materials.This project will utilize a new concept/methodology, multiscale-driven multiphysics, to tackle the issue which appears difficult to solve with existing methods. The research will first focus on the macroscopic mechanisms underlying thermally induced water flux. For the purpose, thermally induced water flux will be related to the temperature dependence of the contact angle by conducting two sub-tasks: 1. measuring thermally induced water flux with a newly designed research setup, and 2. measuring the contact angle using a modified capillary rise method. Then molecular dynamics analysis will be carried out to reveal the microscopic mechanisms underneath the temperature dependence of the contact angle, which is hypothesized to be attributable to the temperature dependence of vapor adsorption. Finally, adsorption isotherms will be measured to experimentally validate the hypotheses and to couple the frameworks at both macro- and micro-scales, aiming at a physically-based and practically implementable framework for thermally induced water flux. The research is potentially very important as it attempts at breakthroughs via innovations on the theoretical (new theories at both macro and micro-scale), experimental (contact angle and thermally induced flux measurements), and numerical aspects (molecular simulations for water-mineral system). In the long term, the project also serves as an exploratory effort to examine the concept of multiscale-driven multiphysics, for the purpose of enabling solutions to critical historical issues and pressing challenges arising from upcoming applications in sustainability, energy and environmental protection, which more and more involve non-isothermal behavior of soils, and in a broad sense, multiphysics in porous materials.