The accuracy of a model is increased when the orthogonality of a grid is optimized. A perfect grid would have all cells perpendicular to the boundary lines. This is very difficult to achieve and thus for most EFDC models an orthogonality of under 3o is recommended. The orthogonalization tool is used to reduce the orthogonal deviation of a grid. The parameters of this tool are set in CVLGrid Setting Options described earlier in Section 4.12 .
The tool has Orthogonalize Global, Orthogonalize Local and Orthogonalize 1D features as shown in Figure 6 22.
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Figure 6 22 Options for orthogonalizing a grid.
If a global operation is selected the entire grid will be orthogonalized immediately. If a local operation is selected, the user must define two grid nodes and the area of the grid limited by the two points will be orthogonalized. Orthogonalize 1D feature is similar to the Orthogonalize Local option but is only applicable for a 1D grid region. In case the feature is applied for an improper grid region, a warning message will appear.
The change in grid orthogonality before and after applying Orthogonalize Global are shown in Figure 6 23 and Figure 6 24. It may be seen in the first image that the average orthogonality is 20.3. In the second image, after CVLGrid has automatically reduced the orthogonalization, it is only 2.6.
The change in grid orthogonality before and after applying Orthogonalize Local are shown in Figure 6 25 and Figure 6 26.
The change in grid orthogonality before and after applying Orthogonalize 1D are shown in Figure 6 27 and Figure 6 28.
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Figure 6 26 Grid image after applying "Orthogonalize Local"
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Figure 6 27 Grid image before applying "Orthogonalize 1D"
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