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发表于 2006-6-26 16:38:38
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[转帖]精彩网格图片
zz网格质量：
Jacobian(必须为正值，即网格体积必须为正)，网格的正交性，最小边与最大边的比值，扭角(skew angle, skewness)
网格的正交性: 每一个网格的体积和其的长，宽，高的乘积的比A=V/(a*b*c). 所以正交性越好，A就越接近1，因为网格更接近长方体。
Cell skewness is calculated by determining the intersection angles of each individual face and its four adjacent neighbors. The largest of these is considered to be the cell skewness (0.0 implies orthogonality)
Mesh Quality (Tgrid Help)
Mesh quality is determined by four basic measures: clustering, smoothness, skewness, and aspect ratio. The relationship between these criteria and the numerical solution obtained for the computational grid is discussed in detail in Boundary Mesh Quality, and summarized briefly here.
The requirement for clustering is simply that the mesh be fine enough to resolve the primary features of the flow being analyzed. You can control the resolution with the boundary mesh that you start from and also with the parameters that control the generation of the interior mesh.
In a high-quality mesh, the change in size from one face or cell to the next should be gradual (smooth); large differences in size between adjacent faces or cells will result in a poor computational grid because the differential equations being solved assume that the cells shrink or grow smoothly. (Figure 1 illustrates different changes in size for triangular cells.)
Skewness determines how close to ideal (i.e., equilateral or equiangular) a face or cell is (see Figure 2).
Highly skewed faces and cells are unacceptable because the equations being solved assume that the cells are relatively equilateral/equiangular.
Aspect ratio can also be used to determine how close to ideal a face or cell is. The aspect ratio of a face or cell is simply the ratio of the longest edge length to the shortest edge length. For an equilateral face or cell (e.g., an equilateral triangle or a square), the aspect ratio will be 1. For less regularly-shaped faces or cells, the aspect ratio will be greater than 1, since the edges differ in length.
For triangular and tetrahedral faces and cells and for pyramids, you can usually focus on improving the skewness, and the smoothness and aspect ratio will consequently be improved as well. For prisms (including 2D quadrilateral cells), however, it is important to check the aspect ratio and/or the change in size in addition to the skewness, because it is possible to have a large jump in cell size between two cells with low skewness (see Figure 3) or a high-aspect-ratio low-skew cell (such as the quadrilateral on the right in Figure 3).
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