reference

Description

The reference function object computes a field whose values are offset to a reference value obtained by sampling the field at a user-specified location.

The field values are calculated using:

$$\text{ref}_c = s(f_{c}(t) - f_p + f_{off})$$

where:

$\text{ref}_c$ : Field values at cell

$s$ : Optional scale factor (default = 1)

$f_{c}(t)$ : Current field values at cell at this time

$f_p$ : Field value at position

$f_{off}$ : Offset field value (default = 0)

Operands

Operand	Type	Location
input	{vol,surface}<Type>Field	$FOAM_CASE/<time>/<inpField>
output file	-	-
output field	{vol,surface}<Type>Field	$FOAM_CASE/<time>/<outField>

where <Type>=Scalar/Vector/SphericalTensor/SymmTensor/Tensor.

Usage

Example of the reference function object by using functions sub-dictionary in system/controlDict file:

reference1
{
    // Mandatory entries (unmodifiable)
    type            reference;
    libs            (fieldFunctionObjects);

    // Mandatory (inherited) entries (runtime modifiable)
    field           <inpField>;

    // Optional entries (runtime modifiable)
    position    (0 0 0);
    scale       1.0;
    offset      0.0;
    interpolationScheme    cell;

    // Optional (inherited) entries
    result          <fieldResult>;
    region          region0;
    enabled         true;
    log             true;
    timeStart       0;
    timeEnd         1000;
    executeControl  timeStep;
    executeInterval 1;
    writeControl    timeStep;
    writeInterval   1;
}

where the entries mean:

Property	Description	Type	Required	Default
type	Type name: reference	word	yes	-
libs	Library name: fieldFunctionObjects	word	yes	-
field	Name of the operand field	word	yes	-
position	Position to sample	vector	no	<not used>
scale	Scale value	scalar	no	1.0
offset	Offset value	scalar	no	0.0
interpolationScheme	Sampling scheme	word	no	cell

The inherited entries are elaborated in:

• functionObject
• fieldExpression

Example by using the postProcess utility:

postProcess -func "reference(<field>)"

Further information

Tutorial:

• cavity

Source code:

• reference

API:

• Foam::functionObjects::reference

History: Introduced in version v1806