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Depth information needed for creation of model grid nodes

Clearly, it is necessary now to have depth information available if the spacing of interior nodes for the model grid is to be related to depth. This information can be obtained by picking the option {.EDITGROUP.GENNODES}DEPGRID and enter the name of the depth grid file, in this case dep.ngh .

The next step is to lay out a fine resolution Cartesian grid over the working polygon, i.e. over the whole domain in this case. To do so, pick option DEPMESH. This brings up a right hand panel which has options for controlling the mesh created and the type of display. Once again, quantities shown in cyan colour can be changed if picked with the mouse. On picking 'Display grid' to toggle ON display of the Cartesian grid, and then 'ACCEPT', you will see a default grid laid out over the working polygon. The fact that the default mesh size, 0.312 problem length units, is much greater than the spacing of the boundary nodes would eventually lead to poorly shaped triangles near the boundaries: a smaller mesh size is advisable in this case.

Before setting up a finer grid, clear the existing Cartesian grid from the screen by backing up till you find option DISPLAY, then pick {DISPLAY}REFRESH. Now once again pick {.EDITGROUP.GENNODES}DEPMESH and this time pick on the default mesh size value '0.312' and enter the smaller value 0.125 for the mesh size. Toggle 'Display grid' to ON and pick ACCEPT to see the recommended finer mesh grid to use for the demonstration case. Note that option DEPMESH also results in evaluation of water depth at the centre of every mesh of the Cartesian grid. The resulting mesh is shown in Figure 3.1.

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