Initial Mesh Generation Research Articles

Heat Production Capacity Simulation and Parameter Sensitivity Analysis in the Process of Thermal Reservoir Development

The development of a geothermal system involves changes in the temperature field (T), seepage field (H), stress field (M), and chemical field (C) and the influence among them and injecting the heat extraction working fluid into the injection well that flows (migrating) through natural fractures and exchanges heat with the geothermal high-temperature rock. At the same time, the injection of low-temperature working fluid will induce thermal stress, resulting in changes in the reservoir temperature field and stress field. To study the influence factors and influence degree of heat production performance and mining life under multi-field coupling in the process of thermal reservoir development, based on THMC multi-field coupling numerical simulation software, this paper deeply studies the control differential equations and boundary coupling conditions of rock mass (fracture) deformation, seepage, heat exchange, the chemical reaction, and other processes based on the numerical solution method of the discrete fracture network model, simulating heat production capacity during the deep geothermal resource extraction process. The reservoir geological model analysis and generalization, parameter setting, boundary conditions, initial condition settings, mesh generation, and other steps were carried out in turn. Two different heat extraction working fluids, water, and CO2 were selected for numerical simulation in the mining process. The changes in the thermal reservoir temperature, net heat extraction rate, and SiO2 concentration during the thirty years of systematic mining were compared. The results show that CO2 has a better heat extraction effect. Finally, the reservoir thermal conductivity, heat capacity, well spacing, injection temperature, fracture spacing, fracture permeability, fracture number, fracture length, and other parameters were set, respectively. The parameter variation range was set, and the parameter sensitivity analysis was carried out. The numerical simulation results show that the engineering production conditions (injection temperature, well spacing) have little effect on the thermal efficiency and mining life, and the properties of fractures (fracture permeability, fracture number, fracture length) have a great influence.

Adaptive Tetrahedral Mesh Generation of 3D Heterogeneous Objects

ABSTRACTIn this paper, a step-wise tetrahedral mesh generation method is introduced to solve the adaptive meshing problems of 3D heterogeneous objects, in which both the material heterogeneity and the geometric complexity have to be taken into account. In light of that, the proposed meshing strategy embraces three steps: initial mesh generation, material-oriented refinement, and geometry-oriented refinement. In the material-oriented refinement, a global refinement algorithm based on optimal Delaunay triangulation (ODT) is designed to control the mesh adaptation in terms of the material distribution. Compared to the refinement strategies based on local modifications, the global refinement algorithm takes full advantages of the material heterogeneity information and distributes the material composition variation over elements as equally as possible. As a result, the number of elements is reduced to a great extent regarding a given material threshold. Implementations show that the proposed approach guarantee...

Three-dimensional surgical simulation

In this article, we discuss the development of methods for computer-aided jaw surgery, which allows us to incorporate the high level of precision necessary for transferring virtual plans into the operating room. We also present a complete computer-aided surgery system developed in close collaboration with surgeons. Surgery planning and simulation include construction of 3-dimensional surface models from cone-beam computed tomography, dynamic cephalometry, semiautomatic mirroring, interactive cutting of bone, and bony segment repositioning. A virtual setup can be used to manufacture positioning splints for intraoperative guidance. The system provides further intraoperative assistance with a computer display showing jaw positions and 3-dimensional positioning guides updated in real time during the surgical procedure. The computer-aided surgery system aids in dealing with complex cases with benefits for the patient, with surgical practice, and for orthodontic finishing. Advanced software tools for diagnosis and treatment planning allow preparation of detailed operative plans, osteotomy repositioning, bone reconstructions, surgical resident training, and assessing the difficulties of the surgical procedures before the surgery. Computer-aided surgery can make the elaboration of the surgical plan a more flexible process, increase the level of detail and accuracy of the plan, yield higher operative precision and control, and enhance documentation of cases.

On the Parallelization of Self-Adaptive hp-Finite Element Methods Part I. Composite Programmable Graph GrammarModel

The paper present the composite programmable (CP) graph grammar model of the selfadaptive hp Finite Element Method (hp-FEM) algorithm. The model incorporates the process of the initial mesh generation, direct solver execution, as well as mesh transformations resulting from selectedoptimal hp refinements. The computational mesh is represented by the CP-graph. The operations performed over the mesh are expressed by the graph grammar productions. The graph grammar model allows for the definition of the computational tasks for the Partitioning, Communication, Agglomeration and Mapping (PCAM) method of the parallelization of the self-adaptive hp-FEM algorithm.

Feature-based fuzzy control adaptive finite-element mesh generation for electromagnetic fields

Considering the feature-based initial mesh generation and the a posteriori error estimator, a fuzzy control adaptive finite-element mesh generation method is presented. The error of potential derivative of each element is regarded as the input of fuzzy controller. Fuzzy rules and reasoning mechanism are constructed. Consequently, the size of the elements and refinement of mesh can be controlled. Applications suggest that this method has advantages such as fast convergence and reasonable element distribution, with strong adaptation.

Three-dimensional unstructured mesh ocean modelling

In this article the advantages and current status of unstructured mesh ocean modelling are reviewed. Future challenges are discussed along with the potential of resulting methods to make a significant impact on ocean modelling over the next decade. These methods are important because they are the only techniques that can simultaneously resolve both small and large scale ocean flows while smoothly varying resolution and conforming to complex coastlines and bathymetry. Realising the full potential of such methods will necessitate the use of dynamic mesh adaptivity. A number of techniques need to be combined and developed from different numerical modelling and geophysical fluid dynamics disciplines in order to create a powerful unstructured mesh ocean model. These are: accurate and robust methods for the discretisation and advection of tracers, density and momentum; the choice of element/cell and satisfaction of the LBB stability condition; representation of hydrostatic and geostrophic balance; the ability to deal with sigma coordinate-like errors associated with the use of unstructured meshes; initial mesh generation to follow complex bathymetry and coastlines; sub-grid scale modelling on unstructured and possibly solution adaptive meshes; scalable solvers and parallel computing. A good solution to each problem is required, and thus the resulting model may be argued to be considerably more complex than traditionally used structured mesh models. It is these topics that are addressed here.

CBC substitution: an adaptive approach for dynamic simulation

This paper introduces an adaptive meshing algorithm to handle problems in dynamic finite element analysis and runtime simulation, where mesh re-generation or dynamic adjustment is required. Based on a concept called CBC (coded box cell) Substitution, this algorithm can be applied to both initial mesh generation and dynamic mesh adjustment along the border zones of multiple primitives that form an entire model. During the initial mesh generation, appropriate labels are assigned to the nodes and the faces of each finite element. These labels are used to facilitate decision-makings in dynamic mesh adjustment. A mapping technique is adopted to transform curved surfaces to plain ones for the ease of automatic mesh adjustment while still using the same algorithm. The meshing examples show that a finite element mesh can be adjusted dynamically and locally around its border zone; and the algorithm can be utilised effectively to simulate the thermal behaviour of a device under real operating conditions.

A novel meshing algorithm for dynamic finite element analysis

This paper describes a new algorithm to handle problems in dynamic finite element analysis and run-time simulation, where mesh re-generation or dynamic adjustment is required. Based on a concept called coded box cell (CBC) substitution, this algorithm can be applied to both initial mesh generation and dynamic mesh adjustment along the border zones of multiple primitives that form an entire model. During the initial mesh generation, appropriate labels are assigned to the nodes and the faces of each finite element. These labels are used to facilitate decision-making in dynamic mesh adjustment. A mapping technique is adopted to transform curved surfaces to plain surfaces for the ease of automatic mesh adjustment while still using the same algorithm. The results of a case study show that a finite element mesh can be adjusted dynamically and locally around its border zone; and the algorithm can be utilized effectively to simulate the thermal behavior of a device under real operating conditions.

Intelligent Initial Finite Element Mesh Generation for Solutions of 2D Problems

The new strategy for non-uniform initial FE mesh generation is presented in this paper. The main focus is set to a priori procedures that define the sizing function independent on the mesh generation algorithm. The sizing function used by the mesh generation algorithm is established by control sphere and control space concepts and fully controls mesh gradation in the complex 2D problem domains.

An adaptive mesh generator based on nodal errors

In this paper, an adaptive mesh generator based on nodal errors is presented. The mesh generator is implemented using the nodal spacing values in order to concentrate elements on the area where estimated errors obtained from a finite element calculation is large. Especially, the sensitivity of energy of the nodal position is used to decide the nodal errors. The nodal spacing values for the initial mesh generation are given to the average values of distances from the node to the neighboring nodes. The next adaptive refinement stages are performed after updating the spacing values using the previous adaptive solution. The Delaunay algorithm is applied to the generation of both an initial mesh and a refined one. To show the practical behavior of the mesh generator, we investigate the energy and the maximum nodal error convergences with the results of magnetostatic finite element calculations on the refined meshes.

Selected projection methods to improve the convergence of non‐linear problems

Short computation times required for the design and numerical optimisation of electromagnetic devices with the finite element method are obtained using an adaptive mesh refinement algorithm. Less time is spent on the initial mesh generation, while the time needed for refinement is negligible when special data structures are used. But an even more significant reduction in total computation time is achieved with the initialisation of the solution on the generated mesh. Fewer Newton steps are required to solve non‐linear problems compared to a zero initial solution, while the time needed for the projection of the solution is far less than the time needed for a Newton step.

A Self-Organizing Mesh Generation Program

A two-dimensional mesh generation program producing quadrilateral elements is presented. It uses a modular, flexible input scheme, and incorporates some existing techniques of initial mesh generation. Some new, more powerful mesh smoothing techniques are developed, and automatic mesh restructuring techniques are coupled with smoothing techniques to produce improved meshes without user interaction.