28.8 Isosurfaces

If you want to display results on cells that have a constant value for a specified variable, you will need to create an isosurface of that variable. Generating an isosurface based on $x$, $y$, or $z$ coordinate, for example, will give you an $x$, $y$, or $z$ cross-section of your domain; generating an isosurface based on pressure will allow you to display data for another variable on a surface of constant pressure. You can create an isosurface from an existing surface or from the entire domain. Furthermore, you can restrict any isosurface to a specified cell zone.

Note that you cannot create an isosurface until you have initialized the solution, performed calculations, or read a data file.

To create an isosurface, you will use the Iso-Surface dialog box (Figure  28.8.1).

Surface $\rightarrow$ Iso-Surface...

Figure 28.8.1: The Iso-Surface Dialog Box

The steps for creating the isosurface are as follows:

1.   Choose the scalar variable to be used for isosurfacing in the Surface of Constant 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.   If you wish to create an isosurface from an existing surface (i.e., generate a new surface of constant $x$, $y$, temperature, pressure, etc. that is a subset of another surface), choose that surface in the From Surface list. If you do not select a surface from the list, the isosurfacing will be performed on the entire domain. You can specify the cell zone on which you want to create an isosurface by selecting the zone in the From Zones list. If you do not select a zone from the list, then the isosurfacing will not be restricted to any cell zone and will run through the entire domain.

3.   Click on the Compute button to calculate the minimum and maximum values of the selected scalar field in the domain or on the selected surface (in the From Surface list). The minimum and maximum values will be displayed in the Min and Max fields.

4.   Set the isovalue using one of the following methods. (Note that the second method will allow you to define multiple isovalues in a single isosurface.)

• You can set an isovalue interactively by moving the slider with the left mouse button. The value in the Iso-Values field will be updated automatically. This method will also create a temporary isosurface in the graphics window. Using the slider allows you to preview an isosurface before creating it.

  Even though the isosurface is displayed, it is only a temporary surface. To create an isosurface, use the Create button after deciding on a particular isovalue.

• You can type in isovalues in the Iso-Values field directly, separating multiple values by white space. Multiple isovalues will be contained in a single isosurface; i.e., you cannot select subsurfaces within the resulting isosurface.

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., z-coordinate-6). (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 Create button. The new surface name will be added to the From Surface list in the dialog box.

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.