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28.1.1 Displaying the Grid

During the problem setup or when you are examining your solution, you may want to look at the grid associated with certain surfaces. You can display the outline of all or part of the domain, as shown in Figure  28.1.1; draw the grid lines (edges), as shown in Figure  28.1.2; draw the solid surfaces (filled grids) for a 3D domain, as shown in Figure  28.1.3; and/or draw the nodes on the domain surfaces, as shown in Figure  28.1.4.

See also Section  28.1.5 for information about displaying the grid on a surface that sweeps through the domain.

Figure 28.1.1: Outline Display

Figure 28.1.2: Grid Edge Display

Figure 28.1.3: Grid Face (Filled Grid) Display

Figure 28.1.4: Node Display

Steps for Generating Grid or Outline Plots

You can draw the grid or outline for all or part of your domain using the Grid Display panel (Figure  28.1.5).

Display $\rightarrow$ Grid...

Figure 28.1.5: The Grid Display Panel

The basic steps for generating a grid or outline plot are as follows:

1.   Choose the surfaces for which you want to display the grid or outline in the Surfaces list.

If you want to select several surfaces of the same type, you can select that type in the Surface Types list instead. All of the surfaces of that type will be selected automatically in the Surfaces list (or deselected, if they are all selected already).

Another shortcut is to specify a Surface Name Pattern and click Match to select surfaces with names that match the specified pattern. For example, if you specify wall*, all surfaces whose names begin with wall (e.g., wall-1, wall-top) will be selected automatically. If they are all selected already, they will be deselected. If you specify wall?, all surfaces whose names consist of wall followed by a single character will be selected (or deselected, if they are all selected already).

To choose all "outline'' surfaces (i.e., surfaces on the outer boundary of the domain), click the Outline button below the Surface Types list. If all outline surfaces are already selected, this will deselect them. To choose all "interior'' surfaces, click the Interior button. If all interior surfaces are already selected, this will deselect them.

2.   Depending on what you want to draw, do one or more of the following:

  • To draw an outline of the selected surfaces (as in Figure  28.1.1), select Edges under Options and Outline under Edge Type. If you need more detail in the outline display of a complex geometry, see the description of the Feature option, below.

  • To draw the grid edges (as in Figure  28.1.2), select Edges under Options and All under Edge Type.

  • To generate a filled-grid display (as in Figure  28.1.3), select Faces under Options.

  • To draw the nodes on the selected surfaces (as in Figure  28.1.4), select Nodes under Options.

3.   Set any of the options described below.

4.   Click the Display button to draw the specified grid or outline in the active graphics window.

If you choose to display filled grids, and you want a smoothly shaded display, you should turn on lighting and select a lighting interpolation method other than Flat in the Display Options panel or the Lights panel.

If you display nodes, and you want to change the symbol representing the nodes, you can change the Point Symbol in the Display Options panel. See Section  28.2.7 for details.

Grid and Outline Display Options

The options mentioned in the procedure above include modifying the grid colors, adding the outline of important features to an outline display, drawing partition boundaries, and shrinking the faces and/or cells in the display.

Modifying the Grid Colors

FLUENT allows you to control the colors that are used to render the grids for each zone type or surface. This capability can help you to understand grid plots quickly and easily. To modify the colors, open the Grid Colors panel (Figure  28.1.6) by clicking on the Colors... button in the Grid Display panel.

Figure 28.1.6: The Grid Colors Panel

(Note that you can set colors individually for the grids displayed on each surface, using the Scene Description panel.)

By default, the Color by Type option is turned on, allowing you to assign colors based on zone type. To change the color used to draw the grid for a particular zone type, select the zone type in the Types list and then select the new color in the Colors list. You will see the effect of your change when you next display the grid. Note that the surface type in the Types list applies to all surface grids (i.e., grids that are drawn for surfaces created using the panels opened from the Surface menu) except zone surfaces.

If you prefer to use the colors FLUENT assigns by zone ID, then you can display the grid using the Color by ID option.

Adding Features to an Outline Display

For closed 3D geometries such as cylinders, the standard outline display often will not show enough detail to accurately depict the shape. This is because for each boundary, only those edges on the "outside'' of the geometry (i.e., those that are used by only one face on the boundary) are drawn. In Figure  28.1.7, which shows the outline display for a complicated duct geometry, only the inlet and outlet are visible.

Figure 28.1.7: Standard Outline of Complex Duct

Figure 28.1.8: Feature Outline of Complex Duct

You can capture additional features using the Feature option in the Grid Display panel. (See Figure  28.1.8.) Turn on Feature under Edge Type, and then set the Feature Angle. With the default Feature Angle of 20, if the difference between the normal directions of two adjacent faces is more than 20 $^\circ$, the edge between those faces will be drawn. Decreasing the Feature Angle will result in more edge lines (i.e., more detail) being added to the outline display. The appropriate angle for your geometry will depend on its curvature and complexity. You can modify the Feature Angle until you find the value that yields the best outline display.

Drawing Partition Boundaries

If you have partitioned your grid for parallel processing, you can add the display of partition boundaries to the grid display by turning on the Partitions option in the Grid Display panel.

Shrinking Faces and Cells in the Display

If you need to distinguish individual faces or cells in the display, you may want to enlarge the space between adjacent faces or cells by increasing the Shrink Factor in the Grid Display panel. The default value of zero produces a display in which the edges of adjacent faces or cells overlap. A value of 1 creates the opposite extreme: each face or cell is represented by a point and there is considerable space between each one. A small value such as 0.01 may be large enough to allow you to distinguish one face or cell from its neighbor. Displays with different Shrink Factor values are shown in Figures  28.1.9 and  28.1.10. Remember that you must click Display to see the effect of the change in Shrink Factor.

Figure 28.1.9: Grid Display with Shrink Factor = 0

Figure 28.1.10: Grid Display with Shrink Factor = 0.01

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