Study On Body-Fitted Coordinate Grid Generation For Mold Filling Simulation Of Casting Processing

Casting manufactures play an important role for the economy development. Numerical modeling of casting processes can help us to optimize the casting processes and improve the quality of products. The research of this thesis is focused on a study on grid generation which is an important part of modeling filling simulation in casting processing. The main finished research work is as follows.First, a grid generation method based on the orthogonal coordinate system is presented. Based on previous grid generating methods of the orthogonal coordinate, a slice line scanning algorithm for grid generation of entity described by STL format files was developed, in which a novel method was proposed to deal with the oddity points.Second, the research on the grid generation based on the body-fitted coordinate (BFC) system has been carried out. The BFC grid can improve the calculation precision and efficiency for the mold filling simulation of complicated and curved-shape castings. The elliptic differential equation method was adopted for two-dimensional (2-D) and three-dimensional (3-D) BFC grid generation. This method can generate stable grid and is suitable to an arbitrary complicated domain. The transform equation between the physical system and calculation system was deduced, which was discretized using the central difference method. The Thomas-Middlecoeff source-term-correction method was applied to generate the 2-D and 3-D BFC grids. The results show that this method can control BFC grids to be orthogonal to the boundaries of the physical domain. A Gauss-elliptic system for grid generation of curve surface is also presented. The transform equation between the 3-D curve surface and 2-D calculation plane was deduced, by which the BFC grids for a 3-D curve surface can be generated in 2-D domain. Furthermore, a multi-block grid generation technique was developed and applied to the BFC grid generation of the complex 2-D plane and 3-D entity. The effects of different boundary conditions and governing function on grid generation results are discussed.Based on the developed algorithm of grid generation, a 3-D orthogonal grid generation program and a BFC grid generation program are developed. The application results show that the orthogonal grid generation program is able to efficiently generate the entities with various geometries. On the other hand, the BFC grid generation program can accurately generate the grids for the complicated and curved-shape entities. The generated BFC grids are adapted well to the boundary with a good grid distribution in the physical domain.