Inputs to expressions

You can include the following inputs in the formula for a CAE expression:

• Punctuation

• Constants

• Functions

• Other expressions

• Variables

• Fields

• Measurements

• Mathematical operators

• Units

• Complex numbers

Punctuation

Parentheses, brackets, and quotation marks are the only punctuation symbols that are valid in the formula of an expression. You can use parentheses in the following ways:

• As part of a text string.Example: Table Field(1)

• To delimit the argument of a function.Example: abs(-2)

• To prescribe the order of mathematical operations.Example: (3/(9+2))

All parentheses that are included in the formula for an expression must be closed. For example, (3/(9+2) is invalid.

Use brackets to designate units. For example, [m] designates meters.

You must place quotation marks around any string constant in the formula for an expression. String constants are text strings that are the names of curves, fields, points, and variables. For example, suppose that Table Field(1) is a field name. To include it in the formula for an expression, you type:

“Table Field(1)”

All quotation marks that are included in the formula for an expression must be closed. For example, fd(“Table Field(1)) is invalid.

Constants

Constants include real numerical values and Boolean constants such as true and false.

When you include a constant in the formula for an expression, you simply type the constant. You do not need to enclose the constant in quotation marks. For example, to enter the integer 2 in the formula for an expression, you type:

2

Functions

The expression system contains a library of functions, many of which are supported in CAE expressions. The functions that are supported in CAE expressions include mathematical functions, lookup functions, and special purpose utility functions.

The mathematical functions are trigonometric, logarithmic, exponential, statistical, and so on. The lookup functions return numerical values for physical quantities, fields, and variables at specific lookup points.

When you enter a function in the formula for an expression, you type the function name and append the argument of the function in parentheses. Depending on the function, the argument might be a number, a variable name, a point name, a field name, or an expression name.

For example, to take the absolute value of –3.0, you type:

abs(-3.0)

The argument of some functions allows for multiple entries. For example, to find the minimum value of 3,7,1,9,14, you type:

min(3,7,1,9,14)

For a listing of mathematical functions, lookup functions, and utility functions that are commonly used in CAE expressions, see Mathematical functions in expressions, Lookup functions in expressions, and Utility functions in expressions.

CAE expressions also support a suite of functions for use with the Simcenter 3D Thermal solver. For a listing of these functions, see Thermal-flow functions in expressions.

You can also create user-defined functions and include them in the formulas for expressions.

Other expressions

You can include expressions in the formula for an expression.

For example, suppose you create an expression for force as a function of time that you name force_vs_time. To include it in the formula for another expression, you type:

force_vs_time

Because expression names are not string constants, you do not need to enclose the expression name in quotation marks.

Variables

Variables are fundamental spatial and non-spatial quantities that vary in the model and are understood by the expression system. The software predefines variables. You cannot create a variable. To include a variable in the formula for an expression, you use the UG variable function.

For example, temperature is a variable. To include it in the formula for an expression, you type:

ug_var(“temperature”)

where temperature is the variable name for temperature. Because variable names are string constants, you must enclose them with quotation marks.

When the software evaluates the formula for the expression, it uses the value of the temperature that corresponds to the current state, which, depending on the application, might be defined by the current position and time.

For a complete listing of variables that you can use in CAE expressions, in the Simulation Navigator, right-click the Fields node and choose Named Variables.

Auto-generated expressions

In the CAE expression system, the software automatically generates expressions for a set of commonly used variables. For many of these variables, the names of the auto-generated expressions and the variable names are identical. Because you can enter expressions directly in the formulas for other expressions, you do not need to use the UG variable function.

For example, the software auto-generates an expression for temperature. The name of the auto-generated expression is temperature. To include the temperature variable in the formula for an expression, you can type:

temperature

In this example, temperature is an expression name. Because expression names are not string constants, you do not need to enclose them in quotation marks.

For a complete listing of all the variables for which the software auto-generates expressions and the corresponding expression names, see Auto-generated expressions.

The software also auto-generates expressions for any variables that you use to define the independent and dependent domains of a field that otherwise would not be auto-generated. For example, suppose you select strain as the independent variable of a field. When you create the field, the software auto-generates an expression named strain. To include the strain variable in the formula for an expression, you can type:

strain

where strain is an expression name.

All expression names must be unique, and certain characters are not used in auto-generated expressions. For more information on these topics, see Restrictions on auto-generated expressions.

Fields

Fields and expressions are similar in that you can use both to represent functional relationships. For instance, an expression is required to define the relationship between the independent and dependent domains of a formula field. Conversely, you can reference any type of field in an expression.

For more information on how to use fields in expressions, see Fields in expressions.

Measurements

Because the software creates expressions for measurements, you can include measurements in the formula for an expression. The measurements can be system-defined expressions that the software generated when you created the underlying geometry of your model, or they can be user-defined expressions that you created.

Because the names of measurements are expression names and expression names are not string constants, you do not need to enclose measurement names in quotation marks.

Mathematical operators

The expression system supports a wide range of algebraic, logical, and conditional operators for you to use in the formula for an expression.

For a complete listing of the mathematical operators that you can use in expressions, see Mathematical operators in expressions.

Units

If an expression is dimensional, it has associated units. The numerical values, functions, other expressions, variables, fields, and measurements that comprise the formula for an expression can all have dimensions and associated units.

For a detailed discussion of units in expressions, see Units in expressions.

Complex numbers

The expression system supports complex numbers and some basic complex math operations so that you can define, for example, material properties and boundary conditions for acoustic analysis.

For a detailed discussion of complex mathematics in expressions, see Complex numbers in expressions.

How do I

Change rename and variable prefix settings

Find units and unit designations

Specify a thermal plugin function

Learn more

Restrictions on auto-generated expressions

Fields in expressions

Units in expressions

Migrating expressions that include angular measures

Inconsistent units warnings

Look up more details

Mathematical functions in expressions

Lookup functions in expressions

Utility functions in expressions

Thermal-flow functions in expressions

Auto-generated expressions

Field function

Mapped field function

Mathematical operators in expressions

Temperatures in expressions

Complex numbers in expressions

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