28.9 Clipping Surfaces

If you have created a surface, but you do not want to use the whole surface to display data, you can clip the surface between two isovalues to create a new surface that spans a specified subrange of a specified scalar quantity. The clipped surface consists of those points on the selected surface where the scalar field values are within the specified range. For example, in Figure  28.9.1 the external wall has been clipped to values of $x$ coordinate less than 0 to show only the back half of the wall, allowing you to see the valve inside the intake port.

Figure 28.9.1: External Wall Surface Isoclipped to Values of $x$ Coordinate

To clip an existing surface, you will use the Iso-Clip dialog box (Figure  28.9.2).

Surface $\rightarrow$ Iso-Clip...

Figure 28.9.2: The Iso-Clip Dialog Box

The steps for clipping a surface are as follows:

1.   Choose the scalar variable on which the clipping will be based in the Clip To Values Of drop-down list. First, select the desired category in the upper list. You can then select from related quantities from the lower list. (See Chapter  31 for an explanation of the variables in the list.)

2.   Select the surface to be clipped in the Clip Surface list.

3.   Click on the Compute button to calculate the minimum and maximum values of the selected scalar field on the selected surface. The minimum and maximum values will be displayed in the Min and Max fields.

4.   Define the clipping range using one of the following methods.

• You can set the upper and lower limits of the clipping range interactively by moving the indicator in each dial (i.e., the dial above the Min or Max field) with the left mouse button. The value in the corresponding Min or Max field will be updated automatically. This method will also create a temporary surface in the graphics window. Using the dials allows you to preview a clipped surface before creating it.

  Even though the clipped surface is displayed, it is only a temporary surface. To create the new surface, use the Clip button after deciding on the clipping range.

• You can type the minimum and maximum values in the clipping range directly in the Min and Max fields.

5.   If you do not want to use the default name assigned to the surface, enter a new name under New Surface Name. The default name is the concatenation of the surface type and an integer which is the new surface ID (e.g., clip-density-8). (If the New Surface Name you enter is the same as the name of a surface that already exists, ANSYS FLUENT will automatically assign the default name to the new surface when it is created.)

The surface name that you enter must begin with an alphabetical letter. If your surface name begins with any other character or number, ANSYS FLUENT will not accept the entry.

6.   Click on the Clip button. The new surface name will be added to the Clip Surface list in the dialog box. (The original surface will remain unchanged.)

If you want to delete or otherwise manipulate any surfaces, click on the Manage... button to open the Surfaces dialog box. See Section  28.11 for details.