This Post-Processing operation performs a temporal average on the primitive variables of the assigned solver starting at the timestep pp_averageStartTimestep until pp_averageStopTimestep with an interval of pp_averageInterval.
The operation is triggered by setting one of the following properties

postProcessingOps_<postprocessinginstanceId> = [PP_AVERAGE_PRE]
postProcessingOps_<postprocessinginstanceId> = [PP_AVERAGE_IN]
postProcessingOps_<postprocessinginstanceId> = [PP_AVERAGE_POST]

The PRE and POST modes require restart files of the averaging timesteps.
The IN mode performs averaging done during the solver run, which does not require restartfiles.

Without setting any other property, only the temporal average is calculated for the primitive variables. The average variables will be stored in restartFile_<postdataId>_<globaltimestep>.Netcdf, which will be named "um", "vm", "wm"(3D), "rhom", "pm".

Additional calculations

<MBool> pp_square = true

This property triggers the calculation of the Reynold stresses
\(\left(\begin{array}{ccc} \overline{u^\prime u^\prime} & \overline{u^\prime v^\prime} & \overline{u^\prime w^\prime} \\ \overline{v^\prime u^\prime} & \overline{v^\prime v^\prime} & \overline{v^\prime w^\prime} \\ \overline{w^\prime u^\prime} & \overline{w^\prime v^\prime} &\overline{w^\prime w^\prime} \end{array}\right)\)

as well as \(\overline{p^\prime p^\prime}\).
Increase the number of allocated variables of the postData (noVariables.<postdataId>) solver by 7.

<MBool> pp_skewness = true

This property determines if skewness is computed.
Increase the number of allocated variables of the postData (noVariables.<postdataId>) solver by 3.

<MBool> pp_kurtosis = true

This property determines if kurtosis (and skewness) is computed.
Increase the number of allocated variables of the postData (noVariables.<postdataId>) solver by 3.

<MBool> pp_averageVorticity = true

This property determines if the vorticity is included in the calculation.
Increase the number of allocated variables of the postData (noVariables.<postdataId>) solver by nDim * 2 - 3.

<MBool> pp_averageSpeedOfSound = true

Increase the number of allocated variables of the postData (noVariables.<postdataId>) solver by 1 + nDim.

Special summation

In order to reduce rounding/truncation errors either activate kahan summation, which requires more memory, or two-pass mode, with a higher time cost. Two-pass is not applicable for the IN mode, since mean values are required for computation.

<MBool> pp_twopass = true

<MBool> pp_kahan = true

Restarting Averging

Set the following properties as shown to restart the temporal average:

pp_averageRestart = true

restartFile.<postdataId> = true

Working example

The following example restarts a temporal average calculation of a FV-Solver. In this example the restartTimeStep is between 100000 and 200000.

### Postprocessing instance
postProcessing          = true
noPostProcessing        = 1
postProcessingSolverIds = [0]
postProcessingType_0    = "POSTPROCESSING_FV"
postProcessingOps_0     = ["PP_AVERAGE_IN"]
 
### Postdata
solvertype.1  = "MAIA_POST_DATA"
# 5 primitive variables + 7 square variables + 3 vorticity variables
noVariables.1 = 15
restartFile.1 = true
 
### Properties for PP_AVERAGE_IN
pp_averageStartTimestep = 100000
pp_averageStopTimestep  = 200000
pp_averageInterval      = 5
pp_averageRestart       = true
pp_square               = true
pp_averageVorticity     = true