
To create your own field function, you will use the Custom Field Function Calculator dialog box (Figure 31.5.1). This dialog box allows you to define field functions based on existing functions, using simple calculator operators. Any functions that you define will be added to the list of default flow variables and other field functions provided by the solver.
Define Custom Field Functions...

Recall that you must enter all constants in the function definition in SI units.

The steps for creating a custom field function are as follows:

The range of integers and real numbers that can be stored is as follows:
Note that using a number less than 1e39 may produce inaccurate results, while values less than 1e45 will produce a result of zero.


Be sure that you do not specify a name that is already used for a standard field function (e.g.,
velocitymagnitude); you can see a complete list of the predefined field functions in
ANSYS FLUENT by selecting the
display/contours text command and viewing the available choices for
contours of.

When you click Define, the solver will create the function and add it to the list of Custom Field Functions within the dropdown list of available field functions. The Define push button is grayed out after you create a new function or if the Definition text entry box is empty.
Should you decide to rename or delete the function after you have completed the definition, you can do so in the Field Function Definitions dialog box, which you can open by clicking on the Manage... push button. See Section 31.5.2 for details.
Using the Calculator Buttons
Your function definition can include many basic calculator operations (e.g., addition, subtraction, multiplication, square root). When you select a calculator button (by clicking on it), the appropriate symbol will appear in the Definition text entry box. The meaning of the buttons is straightforward; they are similar to the buttons you would find on any standard calculator. You should, however, note the following:

log10 and
ln will be calculated for values greater than 0. For values less than or equal to 0, the resultant value will be zero.

Using the
Field Functions List
Your function definition can also include any of the field functions defined by the solver (and listed in Section 31.4) or by you. To include one of these variables/functions in your function definition, select it in the Field Functions dropdown list and then click the Select button below the list. The symbol for the selected item will appear in the Definition text entry box (e.g., p will appear if you select Static Pressure).