Computational Studies of Fracture Networks in Particulate Systems

该项目的动机是最近观察到与流体相互作用的紧密堆积的颗粒或颗粒筏中不断演化的裂隙网络。该奖项支持的研究重点是这些系统的计算模型和模拟。模拟将使对它们行为的详细调查成为可能，并有助于回答一些悬而未决的问题，例如为什么颗粒堆积中看似很小的扰动会导致截然不同的断裂模式。紧密堆积的颗粒网络是一种理想化的多孔介质，表面活性剂的注入是驱动裂隙网络生长的动力。流体流动和裂缝扩展之间的这种耦合是许多技术相关问题的核心，包括水力压裂和腐蚀辅助压裂。桌面实验是详细研究粒子系统的简单且经济有效的方法。这项工作包括在北卡罗来纳州的公立小学开展外联活动，在那里将放映骨折网络模拟和实验的电影。这些课堂演示将作为一个起点，向学生介绍基本的编程概念在很小的年龄。该奖项支持的研究旨在利用模拟科学来确定颗粒填充、粒度分布和表面活性剂注入对颗粒系统中裂缝演化的影响。模拟将提供一种方法来考虑超出实验测试实际限制的系统，例如更广泛的颗粒大小和填料配置。在这一过程中，将在应用力学和计算科学方面做出根本性贡献。其中包括：1)基于化学孔弹性的颗粒筏系统破裂理论；2)多尺度、耦合的有限元和分子动力学方法，可以处理从颗粒相互作用的快速尺度到表面活性剂扩散的慢得多的尺度的一系列时间尺度。这些模型和模拟将用于研究最近在颗粒筏断裂动力学方面的实验，重点是颗粒非均质性和表面活性剂注入的重要作用。

This project is motivated by recent observations of evolving fracture networks in tightly-packed systems of particles, or particle rafts, interacting with fluids. Research supported by this award is focused on computational models and simulations of these systems. Simulations will enable detailed investigations into their behavior, and help to answer open questions such as why seemingly small perturbations in particle packing give rise to dramatically different fracture patterns. The tightly packed particle network is an idealized porous medium, and the injection of surfactant is what drives the growth of the fracture networks. This type of coupling between fluid flow and crack growth is central to many problems of technological relevance, including hydraulic fracturing and corrosion-assisted fracture. The tabletop experiments are simple and cost effective to study particle systems in detail. The effort involves outreach activities to public elementary schools in North Carolina, where movies of the simulations and experiments of fracture networks will be shown. These in-class demonstrations will be used as a launching point to introduce students to basic programming concepts at a young age. The research supported by this award is aimed at using simulation science to determine the influence of particle packing, size distributions, and surfactant injection on fracture evolution in particulate systems. The simulations will provide a means to consider systems beyond the practical limits of experimental testing, such as a much broader range of particle sizes and packing configurations. In the process, fundamental contributions will be made in applied mechanics and computational science. These include: 1) a chemo-poro-elasticity based theory for the fracturing of particulate raft systems; and 2) multi-scale, coupled finite-element and molecular dynamics methods that can handle a range of time-scales, from the fast scales of particle interactions to the much slower scales of surfactant diffusion. These models and simulations will be used to study recent experiments in the dynamics of fracture of particulate rafts, focusing on the important roles of particle heterogeneity and surfactant injection.