Function objects are added by pasting the code into the functions() section of the controlDict file. For a large number of objects it is recommended to include them from separate files. This allows to keep track of the function objects in use and to comment or uncomment them easily. The function objects are executed during rum time. This on-the-fly post-processing doesn't require to keep the field data.
Probes are the simplest way to monitor your simulation without loading the result fields. Everytime the simulation is (re)started a new time folder is generated and the probe file created.
Line sampling can be used to monitor velocity profiles, etc. Each written time step is saved in a new time folder. Each line and variable is saved to a separate file. If the resulting lines have missing points, the interpolation setting should be set to a simpler scheme.
This code writes a VTK surface file periodically into the postProcessing folder.
If interpolate is set to true, the data is saved at the nodes of the surface mesh.
It's stored in the cell centers otherwise. The first option looks smoother, but
produces slightly larger files. The option triangulate allows to convert all surface mesh
elements into triangles. A triangle surface is easier to post-process, because all elements
have the same number of nodes.
It's not possible to make cuts other than planes with this function object.
In many cases, the planar sampling method is unefficient due to the large number of planes needed. The sampling of a single or multiple patches (boundary conditions) might be a good alternative, especially when monitoring air foils, blades, etc. Specifying all patches will save just the outside surface of the domain.
Field averaging is a must in transient simulations. Here prime2Mean means the
average of the squared perturbations and is related to the standard deviation.
This field is usually not needed in basic simulations.
Averaging should be enabled once the simulations stabilised after the initialisation phase. New foam versions have several features to control the averaging window.
When making movies or debugging a selected variable needs to be saved on the
disk with a small time step. This function object allows to do it without saving
all other variables.
Be careful with the settings. You can fill up your disk within minutes!
This code generates stream lines during run time. Refer to the motorcycle tutorial for more information.
This function object allows to track the min and max values of selected variables during run time. The location where the min and max were found is returned. An abnormal behaviour of the simulation can be detected quickly.
OpenFoam provides a general function object to perform calculation on cell faces. These faces are commonly grouped to a patch (boundary condition) or a face zone created by the user. The operations can be various types of integration or averaging. The sumation of the flux phi on a patch will result in a mass flow rate, a value commonly monitored in transient simulations.
This is a general function object which allows to perform a mathematical operation
like average, itegration, min, max, etc on cells: the whole mesh or just a cell zone.
A cell zone is a group of cells defined by the user before the simulation using topoSet.
Example applications are: integration of (local) heat release in combustion simulations, averaging in regions of interest, etc.
This swak4foam based object calculates the integrated heat release times coordinate product
needed to track the center of a flame. To get the flame center the value needs to be divided
by the total heat relese which is done as post-processing.
This function object is a generalisation of the standard foam function object for cells and faces, but with an extended set of operations. The specification of own expressions makes it very flexible, once the syntax is understood.
This is a simple function object for dumping fields when some extreme conditions are reached. It's usually used for debugging diverging cases.