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ABSTRACT: In this work, the suitability of several meshing strategies to optimize the CPU time consumption is investigated. The mesh sensitivity strategy is established by applying the basic framework of a coupled hydro-gas-mechanical 3D FEM numerical model to simulate the tests in terms of types of the elements, number of elements and nodes to quantify the influence of different meshes on the accuracy of the test results with regard to optimization of the CPU time consumption. In this study, the problem is represented and the performance and calculation time of both element types and mesh size in the utilized 3D FEM model are checked. To achieve this, both tetrahedral and hexahedral meshes and their refinement/coarsening are generated. Then the performance of the element types and sizes on the test results are compared. This is a main issue for modelling gas injection through clay-based engineered isolation barriers that requires clear up-scaled tests due to full-scale experiments. 1. INTRODUCTION To quantify the physical properties of a phenomenon such as fluid flow, heat transfer, mass transport, and wave propagation, mathematical equations must be utilized. The finite element method (FEM) is a general numerical method that is the most widely used approach for numerically solving engineering problems (partial differential equations) in 2 or 3-dimensional variable space. In order to calculate the solution in the FEM method, the domain must be divided into a discrete number of elements which is referred to as mesh generation. Striking a balance between accuracy and speed is challenging. A large continuous medium can have infinite degrees of freedom (DoF), as a result, to do the FEM modelling, the meshing approach (mesh size and type of element) is the key component to acquire the most accurate and reliable outcomes in the finite element modelling (Cavin et al., 2005). Accuracy depends on both mesh size (the total number of elements) and element type (the shape of individual elements). Mesh size typically refers to the CPU time consumption. The smaller the mesh size becomes the more accurate the result achieves, hence in larger simulations required solving time of the model extends. To achieve the best balance of accuracy and solving time, mesh coarsening (refining) is required. |
