CFD Online Discussion Forums - OpenFoam logfile compression tip

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OpenFoam logfile compression tip

Hi all!

Making simulations in OpenFoam sometimes I get really huge log files. In some cases it can result in hard drive freespace running out! But all information can be useful afterwards and I cannot just redirect output to /dev/null.
So it is necessary to compress output on the fly. One solution in Linux OS is piping it to gzip/bzip2:
openfoamSolver 2>&1 | gzip > log.gz
But worst thing is that gzip blocks log.gz pipe for reading during simulation and one cannot get access to log data until task is finished! The solution is to use "compress" package. To obtain it in Ubuntu use
sudo apt-get install ncompress
Then it is possible
openfoamSolver 2>&1 | compress > log.Z
or make run script, containing

Code:

#!/bin/sh



checkMesh



if [ $? -eq 0 ]; then

    nohup openfoamSolver 2>&1 | compress > logfileName.Z &    

else

    exit -1

fi

Then you have a simulation running at background. Have a coffee break before coming back and analysing results!:)

Continue with logfile

Hi! great post tip, btw..

My problem is a bit different though: I would like to know how it is possible to continue a logfile of a simulation that was interrupted and I wish to resume with the same logfile, without erasing the previous timesteps.

Thx

Jose

Quote:

Originally Posted by jose_rodrig (Post 290918)

My problem is a bit different though: I would like to know how it is possible to continue a logfile of a simulation that was interrupted and I wish to resume with the same logfile, without erasing the previous timesteps.

This can be done with

Code:

foamProgram >> logFile

the double error uses an already existing file. since the simulation will start from the last saved folder, you should delete everything that is written in the logfile after the folder save point.

Great! many Thx

Regards

Compress VTK files

Thanks for the compress tip!

In line with compression of data files, another question.
I commonly create output sample planes using the function object libfieldFunctionObjects.so. The problems is that the planes are only written in uncompressed ascii, so a lot of data is generated (especially for isocontour).
An example

Code:

PlanesVTK

{functions

(



      enabled   true;

      type surfaces;

      setFormat raw;

      surfaceFormat vtk;

      writeFormat binary;

      timePrecision 0;

      interpolationScheme cellPointFace;

      writeCompression compressed;

      functionObjectLibs ("libsampling.so");

      outputControl   timeStep;

      outputInterval  1;

      fields

      (

         magVorticity

      );

      surfaces

      (

         iso_magU0p5

          {

            type        isoSurfaceCell;

            isoField    magU;

            isoValue    0.8;

            interpolate true;

            regularise  false;

          }

      );

   } // END PlanesVTK is

);

creates asci data files of more then 40 MB, whereas I can compress it for almost 80%. The compression write option does not seem to work. Does somebody has an idea how to compress these kind of data output files during the run ?.
Thanks!

Regards,

Eelc

Hello,
have you had any luck exporting slices in vtk binary format?Thanks,
matteo

Hello,

this is very interesting and may be of great helpt to me.
The problem is I don't really understand how you proceed with this compressed file. I mean normally one wants to extract data from this file during runtime (e.g. for plotting residuals). For doing this I need to extract the file and I am as far as before.
What am I missing here?

Best regards,

Kate

Quote:

Originally Posted by makaveli_lcf (Post 213870)

Code:

#!/bin/sh



checkMesh



if [ $? -eq 0 ]; then

    nohup openfoamSolver 2>&1 | compress > logfileName.Z &    

else

    exit -1

fi

Then you have a simulation running at background. Have a coffee break before coming back and analysing results!:)

Edited the log file on a server

Hello,
By mistake I have edited the solver.log output file in the running case. Now the case is running for 65 hours and it is scheduled to run for 300 hours more. The issue is solver.log file is not getting updated anymore. Although I am monitoring the residuals through residuals function object, but I want to see the number of PIMPLE iterations being used so that I can update my Courant Number. Can anyone suggest the way to restart the output log file?

Quote:

Originally Posted by gtarang (Post 663947)

I would stop the simulation and restart the simulation with the latest timestep the log file says. So for example for time = 20.0 the log file is written so you delete all timesteps larger than 20 and restart the simulation. In controlDict you have to edit before restarting the simulation the startTime to latestTime.