Development of a particle simulator for realistic clayey particles considering mechanical and electro-chemical forces - demystify microscopic mechanisms inside the 'house of cards' at micrometer scale

本项目的目的是开发一个真实粘土颗粒的颗粒模拟器。离散单元法是研究颗粒间相互作用的复杂动力学问题的有力工具。于2021财政年度，我们开发了使用挤压三维多边形作为粒子形状的框架，并在身体固定参考系中解决基于单位四元数的粒子旋转。基于这项工作，我们在2022财年的一次国际会议上发表了特邀演讲，并提交了一篇正在审查的期刊论文。DEM方法有三个主要组成部分：1）。粒子几何学和粒子运动学（特别是粒子旋转）; 2）粒子间相互作用（也称为力模型）; 3）邻域检测。自二零二一财年开发第一个组成部分以来，我们的研究重点一直放在第二个组成部分。对于粘土颗粒，存在由分子间相互作用引起的颗粒间粘附力。为了模拟这种力量，我们回顾了现有的研究粘附接触和必要的调整工作。我们专注于两个力模型：宏观的约翰逊-肯德尔-罗伯茨（JKR）理论和微观范德华力为基础的公式推导Anandarajah和陈。对于JKR理论，我们推导出一个力-位移关系，可用于DEM模拟。对于Anandarajah-Chen模型，这是由倾斜的长方体粒子与无限大的壁相互作用，我们研究了必要的变化，以模拟有限尺寸的粒子之间的力。

The purpose of this project is to develop a particle simulator for realistic clayey particles. The Discrete Element Method (DEM) is widely recognized as a powerful tool for investigating the complex dynamics of granular materials from particle-scale interactions. In FY2021, we developed the framework using an extruded 3D polygon as the particle shape and solving unit-quaternion-based particle rotation in the body-fixed reference system. Based on this work, we gave an invited talk at an international conference in FY2022 and submitted a journal paper currently under review. There are three main components to a DEM approach: 1). Particle geometry and particle kinematics (especially particle rotation); 2) Interparticle interactions (also known as force models); and 3) Neighborhood detection. Since the first component was developed in FY2021, our research focus has been on the second component. For clayey particles, there are interparticle adhesion forces resulting from intermolecular interactions. To model such forces, we have reviewed existing research on adhesive contact and worked on necessary adaptations. We focus on two force models: a macroscopic Johnson-Kendall-Roberts (JKR) theory and microscopic Van-der-Waals force based formulation derived by Anandarajah and Chen. For the JKR theory, we derived a force-displacement relation that can be used for DEM simulations. For the Anandarajah-Chen model, which was derived for tilted cuboid particles interacting with an infinite wall, we investigated the necessary changes to model the forces between finite size particles.