[arieljeds]

Hi there, I'm posting again about something I asked a question about a long time ago and then put aside, but I'm still having trouble.. I want to use the postProcessWaves2Foam utility to calculate:

- surfaceElevation
- forces (based on pressures)
- spectra analysis of the velocity within the wake (i.e. for the strouhal number)

I'm really having trouble using any of the utilities because I do not understand the inputs or how to use them properly. I know this is a very vague question but can anyone point me in a direction to help me better understand what the postProcessing source codes actually need to do?? I've been looking through the source code but with a very limited understanding of C++ this is really not doing me any good. For instance, here is my postProcessingProperties file:

deleteParentOutputDirectory false;

regularSpectrum
{
    callName surfaceElevation;

    removeDuplicate true;
   // inputDir surfaceElevationAnyName;

    deltaT 0.25;
    tMin    100.0; // Default: minimum time
    tMax    300.0; // Default: maximum time

    // The action list is a set of processes on the data
    actionList ( interpolateSurfaceElevation powerSpectraFFT write2Ascii removeData );
    //actionList ( banana) ;
    freqBins 4;
    //nFreq 10;
    windowShiftFraction 0.5; 
    //period 2.0;
    allDataSets true;
}

forcesAndMoments
{
   callName forces;
   inputDir postProcessing/sets/300;
   
   removeDuplicate	true; 
   
   deltaT	0.25;
   tMin		100;
   tMax		300; 
   
   actionList ( interpolateForcesAndMoments powerSpectraFFT write2Ascii removeData ); 
   
   freqBins	4; 
   windowShiftFraction	0.5; 
   allDataSets	true; 
 }

I know this is not correct and I am getting this error:

Processing: forcesAndMoments
    Processing sub-action: interpolateForcesAndMoments
        - Interpolation range: [100; 300]
#0  Foam::error::printStack(Foam::Ostream&) in "/home/ariel/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1  Foam::sigSegv::sigHandler(int) in "/home/ariel/OpenFOAM/OpenFOAM-2.4.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3  Foam::postProcessingWaves::interpolationWeights(Foam::List<std::pair<double, int> > const&, Foam::Field<double> const&, Foam::Field<double>&, Foam::List<int>&, Foam::List<int>&) in "/home/ariel/OpenFOAM/ariel-2.4.0/platforms/linux64GccDPOpt/lib/libwaves2FoamProcessing.so"
#4  Foam::interpolateForcesAndMoments::evaluate() in "/home/ariel/OpenFOAM/ariel-2.4.0/platforms/linux64GccDPOpt/lib/libwaves2FoamProcessing.so"
#5  main in "/home/ariel/OpenFOAM/ariel-2.4.0/platforms/linux64GccDPOpt/bin/postProcessWaves2Foam"
#6  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#7  ? in "/home/ariel/OpenFOAM/ariel-2.4.0/platforms/linux64GccDPOpt/bin/postProcessWaves2Foam"
Segmentation fault

I would really really really appreciate anyone who can offer some insight into these basic postprocessing utilities (even a good book that explains the steps?? I want to make the most use of the utilities available but just failing miserably at correct use

[ngj]

Good afternoon,

@Ariel: I never use the postProcessingWaves2Foam utility myself, which is also one of the reasons that it has never been documented. I do all processing in Matlab with various in-house tools, so I will not be able to help you in that regard.
The only reason that I can see for the utility to crash is that you are not trying to read a forces.dat file, but rather the output in sets. Sets sounds as if you are looking at sampled fields and not a time series of forces.

Kind regards,

Niels

[arieljeds]

Hi @ngj,

Thank you very much for your response. Just curious why you don't use the postProcessingWaves2Foam utilities? I'm wanting to use them as I'm having trouble understanding post-processing steps and felt that the utilities could probably help me understand HOW to post-process.

I'm having another issue to do with the velocity: I'm finding that when I measure the velocity in the field using a probe, it is much much lower than expected. If I'm setting the initial wave field as a potentialCurrent with (0.5 0 0), I am then measuring velocities around 0.19. I'm not understanding how it's going so much slower.. could it be related to the relaxation zones? I recall I ran a case with waves and the velocities were closer to what was expected, so I'm confused what happens now when I run with potentialCurrent.

Thanks again for your help

[ngj]

Good morning,

@Ariel:
I am not using the post-processing toolbox simply because we have a lot of in-house tools in Matlab, so it is easier to perform the processing directly in Matlab. It is also a lot more flexible for specific needs (and we mostly work in a Windows environment).

I do not understand what is happening with the probing. Have you tried to make a visual inspection of your results? Plot the probe location in paraview and compare the velocity field with your probed values.

Kind regards,

Niels

[Giannis_Kaz]

Dear Ariel

Could you please explain me (or send the file setup) the way you meassure velocity using a probe? For the time being I am using probes surface elevation and after that the postProcessing utilities to plot surface elevation. I can't find the way 1) set the probes for calculating velocity components and 2) use the postProcess for velocity components.

I would be grateful for your answer

Kind Regards
John
PhD Candidate
Auth, Civil Engineering

Originally Posted by arieljeds

Hi @ngj,

Thank you very much for your response. Just curious why you don't use the postProcessingWaves2Foam utilities? I'm wanting to use them as I'm having trouble understanding post-processing steps and felt that the utilities could probably help me understand HOW to post-process.

I'm having another issue to do with the velocity: I'm finding that when I measure the velocity in the field using a probe, it is much much lower than expected. If I'm setting the initial wave field as a potentialCurrent with (0.5 0 0), I am then measuring velocities around 0.19. I'm not understanding how it's going so much slower.. could it be related to the relaxation zones? I recall I ran a case with waves and the velocities were closer to what was expected, so I'm confused what happens now when I run with potentialCurrent.

Thanks again for your help

[Ahmed Elhanafi]

Hi John,

For me, I include the following into "probeDefinitions" file in constant folder:

VelocitySensors
{
type probeGauge;
outputControl timeStep; // Alternative: outputTime
outputInterval 1;
fields (U);

pointDistribution userDefinedDistribution;
N 3;
xValues uniform 8;
yValues nonuniform List<scalar> 3(-0.05 0.00 0.05);
zValues uniform 1.65;

}

In controlDict file in system folder add the following to the end:

#includeIfPresent "../waveGaugesNProbes/VelocitySensors_controlDict";

This should give you the velocity components in the following path:

..\postProcessing\VelocitySensors\0

I hope this could help.
Kind regards,
Ahmed

Originally Posted by Giannis_Kaz

Dear Ariel

Could you please explain me (or send the file setup) the way you meassure velocity using a probe? For the time being I am using probes surface elevation and after that the postProcessing utilities to plot surface elevation. I can't find the way 1) set the probes for calculating velocity components and 2) use the postProcess for velocity components.

I would be grateful for your answer

Kind Regards
John
PhD Candidate
Auth, Civil Engineering

[Giannis_Kaz]

Dear Ahmed

Thank you very much for your help! This was very useful!

Kind regards
John

Originally Posted by Ahmed Elhanafi

Hi John,

For me, I include the following into "probeDefinitions" file in constant folder:

VelocitySensors
{
type probeGauge;
outputControl timeStep; // Alternative: outputTime
outputInterval 1;
fields (U);

pointDistribution userDefinedDistribution;
N 3;
xValues uniform 8;
yValues nonuniform List<scalar> 3(-0.05 0.00 0.05);
zValues uniform 1.65;

}

In controlDict file in system folder add the following to the end:

#includeIfPresent "../waveGaugesNProbes/VelocitySensors_controlDict";

This should give you the velocity components in the following path:

..\postProcessing\VelocitySensors\0

I hope this could help.
Kind regards,
Ahmed