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28.4.4 Mirroring and Periodic Repeats

If you model the problem domain as a subset of the complete geometry using symmetry or periodic boundaries, you can display results on the complete geometry by mirroring or repeating the domain. For example, only one half of the annulus shown in Figure  28.4.7 was modeled, but the graphics are displayed on both halves. You can also define mirror planes or periodic repeats just for graphical display, even if you did not model your problem using symmetry or periodic boundaries.

Figure 28.4.7: Mirroring Across a Symmetry Boundary

Display of symmetry and periodic repeats is controlled in the Views panel (Figure  28.4.8).

Display $\rightarrow$ Views...

Figure 28.4.8: The Views Panel

For a symmetric domain, all symmetry boundaries are listed in the Mirror Planes list. Select one or more of these boundaries as the plane(s) about which to mirror the display.

For a periodic domain, click the Define... button to open the Graphics Periodicity panel, to access the periodicity parameters. Specify the number of times to repeat the modeled portion by increasing the value of Number of Repeats. If, for example, you modeled a 90 $^\circ$ sector of a duct and you wanted to display results on the entire duct, you would set Number of Repeats to 4.

In some cases, there may be multiple zones with different periodicity in the domain. For example, in turbomachinery problems with multiple blade rows using the mixing plane model, the periodic angles are different for each blade row. One blade may contain 20 blades (18 $^\circ$ periodic angle) and other may contain 15 blades (24 $^\circ$ periodic angle). In such cases select the required cell zone and specify the number of repeats for that particular cell zone.

When you click Set in the Graphics Periodicity panel the graphics display will be immediately updated to show the requested periodic repeats.

Figures  28.4.9 and 28.4.10 shows the display for the sample geometry before and after applying the periodic repeats respectively. In this case the value of Number of Repeats is set to 6 for the 60 $^\circ$ sector (outer part) and to a value of 4 is set for the 90 $^\circ$ sector (inner part) of the geometry.

Figure 28.4.9: Before Applying Periodicity

Figure 28.4.10: After Applying Periodicity

Periodic Repeats for Graphics

To define graphical periodicity for a non-periodic domain, follow these steps:

1.   Click the Define... button under Periodic Repeats in the Views panel.

Figure 28.4.11: The Graphics Periodicity Panel

2.   In the resulting Graphics Periodicity panel (Figure  28.4.11), select the Cell Zone for which you want to specify the number of repeats.

   Associated Surfaces list contains the surfaces associated with the selected cell zone. This is only informative and you can not edit the selection of surfaces in this box.

3.   Specify Rotational or Translational as the Periodic Type.

4.   For translational periodicity, specify the Translation distance of the repeated domain in the X, Y, and Z directions. For rotational periodicity, specify the axis about which the periodicity is defined and the Angle by which the domain is rotated to create the periodic repeat. For 3D problems, the axis of rotation is the vector passing through the specified Axis Origin and parallel to the vector from (0,0,0) to the ( X,Y,Z) point specified under Axis Direction. For 2D problems, you will specify only the Axis Origin; the axis of rotation is the $z$-direction vector passing through the specified point.

5.   Specify Number of Repeats for the selected cell zone.

6.   Click Set in the Graphics Periodicity panel.

7.   Follow the same procedure for other cell zones.

8.   Click Apply in the Views panel to visualize the modified display.

You can delete the definition of any periodicity you have defined for graphics by clicking on the Reset button in the Graphics Periodicity panel.

Note:   For the 3D domain with multiple periodic zones having different periodicity, FLUENT can repeat only grid, contour and vector plots, and not the pathlines and particle tracks. Also if such domain contains, isosurfaces and clip-surfaces, that are associated with a particular cell zone, they are repeated using the same periodicity that is defined for that cell zone. However, if the surface is not associated with any cell zone, you can not specify the periodicity for that surface.

Mirroring for Graphics

To define a mirror plane for a non-symmetric domain, follow the procedure below:

1.   Click the Define Plane... button under Mirror Planes in the Views panel.

Figure 28.4.12: The Mirror Planes Panel

2.   In the resulting Mirror Planes panel (Figure  28.4.12), set the coefficients of X, Y, and Z and the Distance (of the plane from the origin) in the following equation for the mirror plane:

 Ax + By + Cz = \mbox{distance} (28.4-1)

3.   Click the Add button to add the defined plane to the Mirror Planes list. When you are done creating mirror planes, click OK. The newly defined plane(s) will now appear in the Mirror Planes list in the Views panel. To include the mirroring in the display, select the plane(s) and click Apply, as described above.

If you want to delete a mirror plane that you have defined, select it in the Mirror Planes list in the Mirror Planes panel and click the Delete button. When you click OK in this panel, the deleted plane will be removed permanently from the Mirror Planes list in the Views panel.

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© Fluent Inc. 2006-09-20