Field function

Format:

fd("field name",optional_argument1,optional_argument2,.....)

Fields that represent single-variable functions

You can apply the field function to a field that represents a function of a single independent variable. Mathematically, such a function is expressed as f = f(t).

Suppose the Simulation Navigator lists a table field named Table Field(1) that relates how pressure varies as a function of time. To enter this field in the formula for an expression such that pressure is returned at any time for which the expression is evaluated, in the formula, type:

fd(“Table Field(1)”)

Note:

You must enclose string constants in quotes. Names of fields are string constants.

To enter this field in the formula for an expression such that the field is evaluated at a specific time, in the formula, type:

fd(“Table Field(1)”,t0)

where t0 is the numerical value for the specified time.

Fields that represent multi-variable functions

You can apply the field function to a field that represents a function of two independent variables. Mathematically, such a function is expressed as f = f(s,t).

Suppose the Simulation Navigator lists a formula field named Formula Field(1) that defines how pressure varies as a function of time and temperature. To enter this field in the formula for an expression such that pressure is returned for any combination of time and temperature for which the expression is evaluated, in the formula, type:

fd(“Formula Field(1)”)

To enter this field in the formula for an expression such that the field is evaluated at a specific temperature, but over all times, in the formula, type:

fd(“Formula Field(1)”,T0,time)

where T0 is the numerical value for the specified temperature.

Note:

The order of independent variables is given in the Domain group of the dialog box for the field that represents the multi-variable function.

To enter this field in the formula for an expression such that the field is evaluated at a specific time, but over all temperatures, in the formula, type:

fd(“Formula Field(1)”,temperature,t0)

where t0 is the numerical value for the specified time.

To enter this field in the formula for an expression such that the field is evaluated at a specific temperature and a specific time, in the formula, type:

fd(“Formula Field(1)”,T0,t0)

where T0 and t0 are the numerical values for the specified temperature and time, respectively.

In a similar fashion, you can apply the field function to fields that have independent domains with three or four variables.

Embedded mathematical operations

You can embed mathematical operations within the argument of field functions. Any mathematical operation that can be included in an expression can be embedded in a field function specification.

Suppose you want to include Table Field(1) in the formula for an expression with the time variable shifted such that when the expression queries the field function at time t, the field function returns the value of the field at time t+Δt. To do so, in the formula, type:

fd(“Table Field(1)”,time+Δt)

where Δt is the numerical value for the time shift.

Now suppose that you want the time to be shifted as before, but you also want the magnitude of the resulting pressure to be doubled. To do so, in the formula, type:

2*fd(“Table Field(1)”,time+Δt)

Composite functions

Composite functions use the result of one function as the argument for a second function. Mathematically, composite functions can be expressed as f = f(g(t)). To specify composite functions in the formula for an expression, you can nest field functions inside one another.

Suppose the Simulation Navigator lists table fields named Table Field(2) and Table Field(3). Table Field(2) defines how pressure varies as a function of temperature. Table Field(3) defines how temperature varies as a function of the X-coordinate. To enter these fields in the formula for an expression such that pressure is returned at any X-coordinate for which the expression is evaluated, in the formula, type:

fd(“Table Field(2)”,fd(“Table Field(3)”))

You can nest an unlimited number of field functions and you can also embed mathematical operations within the field functions.

Suppose the Simulation Navigator also lists a table field named Table Field(4) that defines how the X-coordinate varies as a function of time. To enter these fields in the formula for an expression such that pressure is returned at any time for which the expression is evaluated, in the formula, type:

fd(“Table Field(2)”,fd(“Table Field(3)”,fd(”Table Field(4)”)))

To shift the time variable such that when the expression queries the field function at time t, the field function returns the value of the field at time t+Δt, in the formula, type:

fd(“Table Field(2)”,fd(“Table Field(3)”,fd(”Table Field(4)”,time+Δt)))

where Δt is the numerical value for the time shift.

You can also nest field functions within field function representations of multi-variable functions.

Suppose the Simulation Navigator lists a table of fields named Table of Fields that defines how pressure varies as a function of frequency and axial coordinate, and a table field named Table Field(5) that defines how the axial coordinate varies with time. To enter these fields in the formula for an expression such that pressure is returned at any frequency and time for which the expression is evaluated, in the formula, type:

fd(“Table of Fields”,frequency,fd(“Table Field(5)”))

Note:

The order of independent variables is given in the Domain group of the dialog box for the field that represents the multi-variable function.

Vector-valued functions

You cannot apply the field function to vector-valued functions directly. However, you can apply the field function to components of the vector-valued function individually.

Suppose the Simulation Navigator lists a formula field named Formula Field(2) that defines how the components of a force varies as a function of time. To enter the X-component of this field in the formula for an expression such that force is returned at any time for which the expression is evaluated, in the formula, type:

fd(“Formula Field(2)”,”force_1”)

Note:

• The component names are listed in the Expressions group of the dialog box for the field that represents the vector-valued function.

• Unlike independent variables, the names of dependent variables are string constants; you must enclose them in quotes in the field function argument.

To enter this component of the field in the formula for an expression such that the field is evaluated at a specific time, in the formula, type:

fd(“Formula Field(2)”,”force_1”,t0)

where t0 is the numerical value for the specified time.

Fields with complex dependent domains

You can use the field function to reference fields with complex dependent domains in expressions.

For example, suppose Table_field is a table field with a complex dependent domain. To use Table_field in the formula for your expression, type:

fd(“Table_field”)

The expression system evaluates Table_field at the current value for the independent domain and returns a complex result.

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