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WOLFSON UNIT OpenFOAM workshop 1 st November 2010 Postprocessing & the black art of scripting Sandy Wright.

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Presentation on theme: "WOLFSON UNIT OpenFOAM workshop 1 st November 2010 Postprocessing & the black art of scripting Sandy Wright."— Presentation transcript:

1 WOLFSON UNIT OpenFOAM workshop 1 st November 2010 Postprocessing & the black art of scripting Sandy Wright

2 WOLFSON UNIT Postprocessing Paraview –Open source, multi-platform –Based on VTK toolkit –http://www.paraview.org/http://www.paraview.org/ –Can compile or download exe ParaFOAM –Reads native FOAM formats –Can be very difficult to install correctly –NOT installed on Iridis

3 WOLFSON UNIT The basics Cell centred data v node centred Filters –Colour by.. –Slice –Clip –Vectors (Glyphs) –Calculator Save Data

4 WOLFSON UNIT Customisation Custom filters (Tools->create custom filter) State files (same can be achieved via python script) Background images (Edit->View settings) Customised colour maps

5 WOLFSON UNIT Adaptability Parallelisation (pvbatch can be run via mpi) State files & filters platform independent (up to a point) Server-client (ie store files on one machine, use graphics processing of the one in front of you) Python scripting...

6 WOLFSON UNIT Visualisation of cases on iridis 1.Run paraview on iridis via X tunnelling/ exceed – slow for large models 2.Tar & Gzip./VTK & processor*/VTK– large files (typically 1-2 GB when zipped) 3.Lower mesh resolution via mapFields– lose resolution, but v useful for quick viewing etc (and smooths out hot spots etc !!) 4.Extract and port surfaces only (100’s of MB only)

7 WOLFSON UNIT Map fields Make new run dir (lets call it low_res) Copy constant & system dirs to low_res dir Make timestep folder (equiv to last time step of full solution) in low_res Create / copy template field data files (eg U, p) in low_res/timestep Create blockMeshDict of required density in low_res/constant/polyMesh Create mapFieldsDict in low_res/system blockMesh >> LOG-map_fields.txt mapFields../full_solution_dir -parallelSource -sourceTime 1803 >> LOG-map_fields.txt

8 WOLFSON UNIT Scripting “A scripting language is a programming language that allows control of applications and the environment etc without requiring compilation.” Unix/Linux –Bourne shell (aka Bash) –C shell –Others(Korn, mudsh, fish, scsh, pysh...) Python “Python is an interpreted, object-oriented, high-level programming language with dynamic semantics”

9 WOLFSON UNIT Shell scripts Basically a copy of what you would type on the command line, but... –Allows decision making (if/else) –Simple (e.g. arithmetic) operators Why –Avoid mistakes in repetitive commands –Incorporation of command line exe’s leads to very powerful tools –Daisy chain different scripts together Redirection ( >>), standard streams (0,1,2...) Example of openfoam running script Example of ‘house keeping’ script

10 WOLFSON UNIT Different shells Shebang ( #!/bin/bash ) Iridis is run on Bourne/Bash Good practise Why Bash –http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/ –Redirecting streams (eg stderr to stdout => 2>&1 ) Mix ‘n’ match

11 WOLFSON UNIT Command line editors Why ? Surely this went out with the punch card.... –Template script file –Repetitive searches in LARGE files SED –sed 's/yourword/myword/g' infile >outfile head –head –n 5 infile > outfile

12 WOLFSON UNIT Python Easy to learn and readable Object orientated –Libraries & routines out there to be used! Lists –a = ['spam', 'eggs', 100, 1234] –>>> a ['spam', 'eggs', 100, 1234] –>>> a[3] 1234 For loops (note indenting) for i in range(24): Example of Paraview python script

13 WOLFSON UNIT Resources http://www.paraview.org/Wiki/ParaView http://www.cfd-online.com/Forums/ > paraview -? Google !!!

14 WOLFSON UNIT Scripting resources http://www.python.org/ http://docs.python.org/tutorial/ http://docs.python.org/release/2.5.2/tut/tut.html http://www.soton.ac.uk/~sesg3020/index.html http://www.hypexr.org/bash_tutorial.php http://tldp.org/LDP/abs/html/ http://www.eng.cam.ac.uk/help/tpl/unix/sed.html http://www.grymoire.com/Unix/Sed.html


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