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

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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.