Feature study of body-fitted Cartesian grids used in casting numerical simulation

A type of mesh called a body-fitted Cartesian mesh, very different from the traditional structured body-fitted mesh, is established. At first, the right parallelepiped mesh is generated, then, a feature analysis is done on the cross sections. These cross sections are the intersections of the casting shape with the right parallelepiped grids (under the Cartesian coordinate system). On the basis of the feature analysis, two sorts of body-fitted boundary grids, shape-keeping grids and shape-distortion grids, are defined. Shape-distortion grids can be removed or weaken by increasing the number of grids or moving the coordinates of the mesh generation region, so actually the body-fitted Cartesian mesh generation is to get shape-keeping grids. A shape-keeping grid mainly consists of two sorts of surfaces (I type face and II type face), and each of them is joined by two types of points (I type point and II type point). If only these two types of points were given, the shape-keeping mesh would be constructed. In this paper, the cases of the above two boundary grids being generated were discussed. An algorithm was put forward to get the shape-keeping grids. Several body-fitted Cartesian meshes generated on castings show the validity of the algorithm. The mesh generation examples show that the body-fitted Cartesian mesh is more excellent than the right parallelepiped mesh in aspects of decreasing grids number and being closer to the shape of the casting solid.