Anisotropic Dispersion and Variable-Density Flow in Fractured Media

本研究旨在研究裂隙介质中的各向异性弥散和与变密度流动相关的对流混合。人们通常没有认识到裂缝系统中的混合模式可以是各向异性的，这是由裂缝网络的几何形状决定的，并且可能偏离经典的各向同性理论。对于裂隙岩体中的不稳定混合流动，研究结果仅限于少数研究。我们提出的研究有很大的机会为裂隙岩石系统中的物理物质输运提供基础知识。目的是阐明裂隙岩石系统中物理质量输运的过程——裂缝几何特征如何影响色散和对流色散。为了实现这一目标，我们建议在具有复杂裂缝几何形状的二维和三维系统中进行质量输运的物理和数值模型研究。我们感兴趣的是探索各向异性色散在变密度系统中发展和表现的条件。这项研究围绕四个不同的任务进行。任务一涉及一系列二维断裂系统的实验室实验。任务2将三维变密度代码MITSU3D扩展到具有渗透性基质块的裂缝网络。任务3旨在通过实验研究具有良好特征的三维裂缝网络中的物理质量输运。任务4是一项补充模型研究，旨在将实验结果与MITSU3D结合使用，以制定适当的方法来播种不稳定性。拟议的研究将通过以下方式促进认识：(i)提供关于裂隙岩石系统中色散和对流色散性质的基础性新知识；（ii）开发和应用复杂裂隙岩石系统中质量输运物理建模的新能力，以及三维示踪剂分布的可视化；（iii）开发和应用离散裂隙系统的新建模方法，这种方法可以适应网络几何和过程的复杂性。

9814820Schwartz This study proposes to investigate anisotropic dispersion in fractured media and convective mixing associated with variable-density flow. It is generally not appreciated that the pattem of mixing in fractured systems can be anisotropic, as determined by the geometry of the fracture network, and can deviate from the classical isotropic theory. In terms of unstable mixed flows in fractured rocks, results are limited to a few studies. There are significant opportunities with our proposed study to contribute ftmdamental knowledge to physical mass transport in fractured rock systems.The goal is to elucidate processes of physical mass transport in fractured rock systems - how dispersion and convective dispersion are influenced by characteristics of the fracture geometry. To achieve this goal we propose to conduct both physical and numerical model studies of mass transport in 2-D and 3-D systems with complex fracture geometries. We are interested in exploring the conditions under which anisotropic dispersion develops and is manifest in variable-density systems.The study is organized around four different tasks. Task I involves a series of laboratory experiments with 2-D fractured systems. Task 2 extends the 3-D variable-density code MITSU3D to fracture networks with permeable matrix blocks. Task 3 is designed to study physical mass transport experimentally in a well-characterized 3-D fracture network. Task 4 is a complimentary model study designed to use the experimental results in conjunction with MITSU3D to develop appropriate methods to seed instabilities.The proposed study will contribute to knowledge by: (i) providing ftindainental new knowledge concerning the nature of dispersion and convective dispersion in fractured rock systems, (ii) developing and applying new capabilities for the physical modeling of mass transport in complex fractured rock systems, and for visualizing tracer distributions in three dimensions, and, (iii) developing and applying new modeling approaches for discrete-fracture systems, which can accommodate complexities in network geometry and in processes.