Computational Studies of Fracture Networks in Particulate Systems

该项目的动机是最近观察到紧密堆积的颗粒或颗粒筏系统中不断发展的裂缝网络，与流体相互作用。该奖项支持的研究重点是这些系统的计算模型和模拟。模拟将有助于详细研究它们的行为，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微小的扰动会导致截然不同的断裂模式。致密的颗粒网络是一种理想的多孔介质，表面活性剂的注入是推动裂缝网络扩展的原因。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。桌面实验简单，成本低，可用于粒子系统的详细研究。这项工作包括在北卡罗莱纳州的公立小学开展外展活动，在那里将放映裂缝网络模拟和实验的电影。这些课堂演示将作为一个起点，向年轻的学生介绍基本的编程概念。该奖项支持的研究旨在利用模拟科学来确定颗粒充填、尺寸分布和表面活性剂注入对颗粒系统裂缝演化的影响。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，例如更大范围的颗粒尺寸和填料配置。在这个过程中，应用力学和计算科学将做出根本性的贡献。其中包括：1)基于化学孔隙弹性的颗粒筏系统压裂理论；2)多尺度、耦合的有限元和分子动力学方法，可以处理一系列时间尺度，从粒子相互作用的快速尺度到表面活性剂扩散的较慢尺度。这些模型和模拟将用于研究颗粒筏断裂动力学的最新实验，重点研究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.