You can add Variables () from either the Global Definitions node or the Definitions node under the Component (local) nodes.

Use the Variables node to define expressions as user-defined variables. Global variables can be used in any context that accepts variable expressions, in all Components and on all geometric entities — provided that their expressions are also global expressions. In contrast, local variables have a specific geometric domain of definition. Such variables can only be used and evaluated in a specific Component, or on selected domains, boundaries, edges, or points.

Global variables are primarily useful for expressions involving parameters that do not depend on the geometry, such as time, or dependent variables in an ODE or algebraic equation. Whenever possible, define variables under Definitions in a Component to minimize the risk of variable name conflicts in the global namespace.

Which variables are available for evaluation in postprocessing is decided at the time a solution is created. This means that variables you define do not immediately show up as predefined quantities in results nodes or become available for use in expressions when postprocessing an existing solution. To access the new variables, you must solve the model or update an existing solution by right-clicking a Study node () and selecting Update Solution ().

Select the geometric scope from the Geometric entity level list: Entire model, Domain, Boundary, Edge (3D only), or Point. For all levels except Entire model, you must also specify the variables domain of definition either by adding entities to a Manual selection or choosing All boundaries, for example, from the Selection list.

In the Variables table or the fields under the table, enter variables by defining a variable name under Name, an expression that define the variable under Expression (see  About Parameters, Variables, Variable Utilities, Physics Utilities, and Expressions), and (optionally) a description that explains the variable under Descriptions. Alternately, you can import variable definitions from a text file. For the expression, press Ctrl+Space or use the Insert Expression button () below the table to choose from a number of applicable variables, parameters, functions, operators, and constants that you can insert into the expression at the position of the cursor. Use other buttons underneath the table to move, insert, and remove rows and to clear the table. Also, use the Move To button () to move selected variables to any other available Variables node or to a new Variables node. You can right-click selected rows in the table to move or remove selected rows, or to insert a row above the selected rows. You can also cut, copy, and paste the selected contents.

Additionally, the Save to File button () saves variables to a text file (or to a Microsoft Excel Workbook spreadsheet if the license includes LiveLink™ for Excel®) for reuse in other models. The information is saved in space-separated columns in the same order as displayed on screen. When saving to Excel, an Excel Save dialog box appears where you can specify the sheet and range and whether to overwrite existing data, include a header, or use a separate column for units.

Using the Load from File button (), you can import or load data in text files created, for example, by a spreadsheet program. Data must be separated by spaces or tabs. If the license includes LiveLink™ for Excel® you can also load variables from a Microsoft Excel Workbook spreadsheet. Then an Excel Load dialog box appears where you can specify the sheet and range, whether to overwrite existing data, and declare if the data is stored using a separate column for units.