POST User Guide  POST Version 9.6.1
General Information

Introduction

POST is a block parallel post-processing tool especially designed for the analysis of flow fields encountered in turbomachinery. It's designed to read the output CGNS file of TRACE, perform all specified post-processing tasks. The intention for the software design was that all users of POST can easily create their own tasks in C, execute them and even share it with other people.

POST

  • prepares data for the visualization
  • reduces data
  • processes TRACE results
  • is MPI parallel

POST is able to

  • understand TRACE configurations
  • calculate derived variables
  • integrate and average
  • intersect
  • transform
  • perform (inverse) Fourier-decomposition

POST automatizes recurring tasks.

Getting Help

  • Read this documentation.
  • Type POST --help
    You will get a general help of POST.
    If you want the help for a specific task type POST --help -option. This gives information on sub-options, prerequisites and (if applicable) component tasks of this task.
  • POST --show -vars gives a list of available variables in POST.
  • POST --show -libs lists libraries POST is currently linked against.

Execution

  • Input-task
    POST --input TRACE.cgns
  • Calculation
    --[Task] [suboptions]
  • Output-task
    --output POST.plt
  • POST works with one data set (sometimes with multiple)
  • Every task edits the data set
  • A task has restrictions (specific solution fields etc.)
  • Blocks, solutions, etc. can be skipped \(\Rightarrow\) no termination
  • Execution order of the tasks \(=\) Order of tasks in the command line

A typical command line call may look this way:

mpirun -np 8 POST -i Trace%d.cgns -vn Pressure Density -ce -dft -ip -gf grid.dat -o Post.cgns

This means:

  • run POST parallel with eight processes
  • read a series of pictures, but only "Pressure" and "Density" and ignore the other variables
  • calculate the "Entropy"
  • perform a discrete Fourier transformation
  • create an analysis surface
  • write the data into a CGNS file
Note
The order of the options is important!
mpirun -np 8 POST -i Trace%d.cgns -vn Pressure Density -o Post%d.cgns -ip -gf grid.dat -ce -dft
This will take longer and you will only get as result "Pressure" and "Density".
If you are not sure what will happen with your command line call, add the option -dotty to get an execution graph.

Derived variables

  • Replace for the most Tecplot equations
    --calcMachAbs
    --calcTemperatureStagnation
    --calcTurbulentLengthScale
    --calcSchlieren
    ...
  • In combination with --interpolateCellCenteredToVertexData and Tecplot-Output
    POST --input TRACE.cgns --calcSchlieren --interpolateCellCenteredToVertexData --output POST.plt
Schlieren calculated with POST

Sub-options

  • A task may have suboptions
  • List them
    POST --help --input
  • Works even in a command line
    POST --input TRACE.cgns --help --calcMach --output POST.cgns
  • Example to create a Tecplot file of all boundaries with the Pressure
    POST --input TRACE.cgns -rbc -vn Pressure --deleteBlock -dim 3 --interpolateCellCenteredToVertexData --output POST2D.plt

Multiple Datasets

  • There are also tasks which reduce multiple input datasets to one output dataset.
    POST \
    --input TRACE.modified.cgns \
    --input TRACE.cgns \
    --calcPressureStagnationAbs \
    --diffFlowFields \
    --interpolateCellCenteredToVertexData \
    --output TRACE.diff.plt
  • Or multiple input datasets will create multiple output datasets. E.g. multiple picture CGNS are processed serially.
    POST \
    --input picture_%d/TRACE.cgns \
    --interpolateCellCenteredToVertexData \
    --output POST%03d.plt