The Study On Two Dimensional Quadrilateral Finite Element Mesh Generation

The dissertation presents a quadrilateral mesh generation algorithm-domain decomposition algorithm-for finite element method, the algorithm is based on a recursive decomposition of the domain into quadrilateral elements. The algorithm automatically generates meshes composed entirely with quadrilaterals over complex geometries. Compared with other mesh generation methods, the mesh generated by this algorithm is with high quality, mesh density is better controlled, mesh is symmetric if the initial domain is symmetric. The dissertation has made some improvements upon original algorithms:(1) The algorithm is not good at decomposing six-node domains. The dissertation classifies six-node domains and decomposes each kind with different scheme.(2) Before domain decomposition, the algorithm generates a layer of elements which is align with boundaries. The final mesh is more suitable for analyzing the problems which is sensitive to boundary conditions.(3) During mesh generation, to select the best split-line from all possible split-lines is a time-consuming process. The dissertation presents a method that decreases the amount of calculations of split-lines without affecting the selection of the best split-line.The author developed a two dimensional FEM preprocessor DecompMesh using the domain decomposition algorithm. The preprocessor has capabilities for modeling, mesh generation, element pattern transforming, material and boundary condition setting, data output. There are some mesh examples at the end of Chapter 3. Chapter 4 makes a brief introduction to tetrahedral mesh generation techniques.