ddt

Description

The ddt function object computes the Eulerian time derivative of an input volume field for time-variant simulations (not appropriate to steady-state simulations).

Operands

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

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

Usage

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

ddt1
{
    // Mandatory entries (unmodifiable)
    type            ddt;
    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: ddt	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 "ddt(<field>)"

Further information

Tutorial:

• cavity

Source code:

• ddt

API:

• Foam::functionObjects::ddt

History: Introduced in version v1712