Post-processing

Function objects

OpenFOAM includes a collection of FunctionObjects that offer users the opportunity to closely manage their computational analyses. These objects can be applied to manipulate the workflow process, and provide a mechanism to extract predicted field and derived quantities at run-time. Alternatively, the actions can be executed afterwards using the execFlowFunctionObjects utility.

The current range of features comprises of:

• Field function objects
• Forces function objects
• Graphics function objects
• grpInitialisationFunctionObjects
• Lagrangian function objects
• Solver function objects
• Utility function objects

Using function objects

Function objects are defined by additional entries in the $FOAM_CASE/system/controlDict input dictionary. Each object is listed in a functions sub-dictionary entry, e.g. the following shows the input options applicable to `output' -type objects:

functions
{
    myFunctionObject    // user-defined name of function object entry
    {
        type                functionObjectType;
        libs                (myFunctionObjectLib);
        region              defaultRegion;
        enabled             yes;
        timeStart           0;
        timeEnd             10;
        evaluateControl     timeStep;
        evaluateInterval    1;
        writeControl        outputTime;
        writeInterval       1;
        ...
    }
}

Where:

Property	Description	Required	Default value
type	type of function object	yes
libs	libraries containing object implementation	yes
region	name of region for multi-region cases	no
enabled	on/off switch	no	yes
timeStart	start time	no
timeEnd	end time	no
evaluateControl	when to evaluate: either 'writeTime' or 'timeStep'	no	timeStep
evaluateInterval	steps between evaluation when evaluateControl=timeStep	no	1
writeControl	when to output: either 'writeTime' or 'timeStep'	no	timeStep
writeInterval	steps between output when writeControl=timeStep	no	1

The sub-dictionary name myFunctionObject is chosen by the user, and is typically used as the name of the output directory for any derived data. The type entry defines the type of function object properties that follow. Since the function objects are packaged into separate libraries, the user must tell the code where to find the function object implementation, identified using the libs entry.