grad

Table of Contents

• Description
  • Operands
• Usage
• Further information

Description

The grad function object computes the gradient of an input field.

The operation is limited to scalar and vector volume or surface fields, and the output is a volume vector or tensor field.

Operands

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

Usage

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

grad1
{
    // Mandatory entries (unmodifiable)
    type            grad;
    libs            (fieldFunctionObjects);

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

    // 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: grad	word	yes	-
libs	Library name: fieldFunctionObjects	word	yes	-
field	Name of the operand field	word	yes	-

The inherited entries are elaborated in:

• functionObject
• fieldExpression

Example by using the postProcess utility:

postProcess -func "grad(<field>)"

Further information

Tutorial:

• $FOAM_TUTORIALS/incompressible/pisoFoam/RAS/cavity

Source code:

• Foam::functionObjects::grad

History

• Introduced in version v1606+