Research On High Resolution CFD Mesh Generation Based On NURBS Surface Triangulation

With the rapid development of Computational Fluid Dynamics, the problems to be solved with CFD are becoming more and more complex.However, the traditional unified body-fitted grids structure has been unable to meet the needs of development of CFD. Unstructured mesh appears and attracts the CFD researchers' attention with new features by breaking the habit of structured thinking. Unstructured mesh is superior to the geometric flexibility. It not only can effectively describe and discrete of complex shape, but also has good general applicability. Moreover, the randomized data structure is very useful for adaptive grids. Thus, it can be better improve the computing efficiency. In this paper, a detailed description of the generation method of unstructured mesh is given, the main works follow:(1) The commonly used methods of unstructured mesh generation technique are summarized by reading relevant books and papers. A detailed comparison of Delaunay method, Advancing Front method and Quadtree/Octree method is given in the paper. By making a contrast of complex shape mesh generated by them, the Delaunay method is used in the paper finally.(2) The triangulation of two-dimensional plain mesh generation is studied.By using the container type and inheritance feature in C++ programming language, the Delaunay triangulation method is realized.A new design of data structure which is more stable and robust is established.(3) The surface triangulation and tetrahedral mesh generation method is studied. A method of structured grids converting to unstructured mesh is adopted as the structure grid generation process has become more and more mature and the parametric supporting line to promote boundary layer is more stable in the Spider software. The Delaunay method is still used to generate tetrahedral mesh. Combining these two points above, prism cells can be obtained in the boundary layer of unstructured mesh. A perfect docking structure between unstructured mesh and structured grids is realized not only in the data structure but the efficiency.(4) The unstructured mesh module-UGCS based on the platform of Spideris established. The algorithms of generation of two-dimensional and three-dimensional unstructured mesh are also included in this module written by C++.And this module has been integrated into the Spider software already.The stability of Spider and the robustness of the unstructured mesh algorithms has been verified through the mesh quality and numerical calculation results of a large number of examples.