The greatest challenge when performing large deformation simulations using the CFD-DEM coupling method lies in the dynamical update of the fluid meshes. To address this problem, a novel CFD-DEM coupling method integrated with the dynamic unstructured grid is proposed in this work. The mesh initialization and reconstruction are performed by the Constrained Delaunay triangulation (CDT) implemented by the tetgen algorithm. Moreover, the equation of state (EOS) is introduced to consider the impact of fluid compressibility. The reliability of this coupling method is preliminarily verified by the particle sedimentation test. Additionally, undrained triaxial shear and one-dimensional consolidation tests are conducted to examine the applicability of the proposed method in simulating geotechnical cases. From our analysis, it is found that the shear responses in the undrained triaxial shear test obtained from the proposed method with dynamic mesh are in direct accordance with those led by the constant volume (CV) method. However, difficulties arise in accurately describing the moving boundary by the fixed mesh, leading to unreliable results. Moreover, in the one-dimensional consolidation test, both the dynamic and fixed grids can capture the Mandel—Cryer effect, which is more pronounced under the dynamic grid, mainly due to the dual impact of the loading device and particle skeleton on the fluid. A greater compressibility specified under the dynamic grid led to a weakening of this effect, whereas its duration is increased. Our work provides valuable insights for effectively dealing with dynamic fluid boundaries.

中文翻译：

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一种新颖的动态非结构化网格未解析/半解析CFD-DEM耦合方法

使用CFD-DEM耦合方法进行大变形模拟时的最大挑战在于流体网格的动态更新。为了解决这个问题，本文提出了一种与动态非结构化网格集成的CFD-DEM耦合方法。网格初始化和重建由tetgen算法实现的约束 Delaunay 三角剖分 (CDT) 执行。此外，引入状态方程（EOS）来考虑流体压缩性的影响。通过颗粒沉降试验初步验证了该耦合方法的可靠性。此外，还进行了不排水三轴剪切和一维固结试验，以检验所提出的方法在模拟岩土工况中的适用性。通过我们的分析，发现由所提出的动态网格方法获得的不排水三轴剪切试验中的剪切响应与恒容（CV）方法得到的剪切响应直接一致。然而，通过固定网格准确描述移动边界会出现困难，导致结果不可靠。此外，在一维固结试验中，动态网格和固定网格均能捕获Mandel—Cryer效应，动态网格下该效应更为明显，这主要是由于加载装置和颗粒骨架对流体的双重影响。动态网格下指定的更大压缩性会导致这种效果减弱，但其持续时间会增加。我们的工作为有效处理动态流体边界提供了宝贵的见解。