The Coarsen Grid option operates in an opposite way to that for Refine Grid. It decreases resolution of the grid. It operates by dividing the existing number of cells in the current grid with I, J directions independently. There are two types for coarsening grid:
Coarsen grid with a selected grid segment
computational 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. In practice, this is very difficult to achieve, and thus, for most EFDC models an orthogonal deviation of less than 3o is recommended. The orthogonalization tool is used to reduce the orthogonal deviation of a grid.
To view the orthogonal deviation of a grid, LMC on the grid layer in the Layer Control
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then RMC on that grid layer to show RMC's options, select Show Properties/Orthogonal Deviation as shown in 1153859831. In addition, the orthogonal deviation of a grid can be viewed from the Grid menu as shown in 1153859831.
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Figure 1 Select . View orthogonal deviation of a grid segment to highlightfrom RMC's option.
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Figure 2 Grid Block Coarsening form. View orthogonal deviation of a grid from Grid menu.
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Figure 3 An example of coarsening grid with a selected grid segment.
Coarsen grid with a selected grid block
. Orthogonal deviation of a grid.
There are two options for orthogonalizing a grid which are to orthogonalize the entire grid or to orthogonalize a grid block as described below:
Othogonalize the entire grid
- Select the grid layer in the Layer Control to select grid the user want to refineSelect Select object by LMC
- From Grid menu, select Orthogonalize Grid, or click on the Orthogonalize grid button from the main toolbar as shown in 1153859831. When this is done the entire grid will be immediately orthogonalized. 1153859831 shows a change in orthogonality of the grid after applying Orthogonalize Grid.LMC on
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Figure 4. Orthogonalize grid.
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Figure 5. Grid image after applying "Orthogonalize Grid"
Orthogonalize a grid block
- Select the grid layer in the Layer Control by LMC
- From the main toolbar, select the Select object button then select a grid node then , hold the Shift key , LMC on and select the second node which is not on same grid segment in I or J direction, the grid grid node. The grid block will be highlighted as shown in 1154482393 1153859831.
- From Next, from Grid menu, select Coarsen Orthogonalize Grid option (or select Coarsen Grid or click on the Orthogonalize grid button from the main toolbar), the Grid Block Coarsening form will be popup . A further option is to select Orthogonalize Grid Block from the RMC options as shown in 1154482393. The user needs to enter the Coarsening Factor then click OK button. 1154482393 show examples for grid coarsening with a selected 1153859831. As a result, the grid block will be immediately orthogonalized. 1153859831 shows a change in orthogonality of the grid after applying Orthogonalize Grid for a grid block.
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Figure 4 6. Select a grid block to highlight.
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Figure 5 7. Select Orthogonalize Grid Block Coarsening formoption.
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Figure 6 An example of coarsening grid with a selected grid block.8. Grid image after applying "Orthogonalize Grid Block"