Das Amiya Prakash, Zhao Jidong, Sweijen Thomas
Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clearwater Bay, Kowloon 999077, Hong Kong, Special Administrative Region of China.
Faculty of Geosciences, Utrecht University, Utrecht 3584 CB, The Netherlands.
Proc Natl Acad Sci U S A. 2025 May 6;122(18):e2420314122. doi: 10.1073/pnas.2420314122. Epub 2025 May 2.
This paper presents pore unit assembly-discrete element model (PUA-DEM), a pore-scale hydromechanical framework that resolves interactions between mobile granular particles and multiphase fluids in unsaturated granular media. The framework uniquely integrates DEM with pore-scale hydrodynamic models to capture unsaturated flow dynamics, while leveraging a two-way coupling mechanism to ensure bidirectional fluid-grain feedback through stabilized domain partitioning. Further innovations include a dynamic pore-merging and retriangulation algorithm that enhances computational efficiency for large-scale systems. Validated against experimental data for glass beads and Ottawa sand, PUA-DEM accurately reproduces critical hydromechanical phenomena-including capillary/viscous fingering, wetting-induced granular swelling/collapse, and quasi-static deformation-under diverse saturation and loading regimes. Numerical case studies reveal how capillary forces and wetting fluid saturation collectively govern granular response, from pore-scale meniscus evolution to macroscale flow instabilities. By bridging pore- and particle-scale physics, PUA-DEM advances predictive modeling of partially saturated granular systems, offering transformative insights for geohazard mitigation, sustainable agriculture, pharmaceutical manufacturing, and energy-related engineering applications.
本文提出了孔隙单元组装离散元模型（PUA-DEM），这是一种孔隙尺度的流体力学框架，用于解析非饱和颗粒介质中移动颗粒与多相流体之间的相互作用。该框架将离散元法与孔隙尺度流体动力学模型独特地整合在一起，以捕捉非饱和流动力学，同时利用双向耦合机制，通过稳定的区域划分确保流体与颗粒之间的双向反馈。进一步的创新包括一种动态孔隙合并和重新三角剖分算法，该算法提高了大规模系统的计算效率。通过与玻璃珠和渥太华砂的实验数据进行验证，PUA-DEM能够准确再现各种饱和度和加载条件下的关键流体力学现象，包括毛细/粘性指进、润湿诱导的颗粒膨胀/坍塌以及准静态变形。数值案例研究揭示了毛细力和润湿流体饱和度如何共同控制颗粒响应，从孔隙尺度的弯月面演化到宏观尺度的流动不稳定性。通过弥合孔隙尺度和颗粒尺度的物理过程，PUA-DEM推动了部分饱和颗粒系统的预测建模，为地质灾害缓解、可持续农业、制药制造以及与能源相关的工程应用提供了变革性的见解。
