CFD Online Discussion Forums - How many probes can I have in a simulation ?

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How many probes can I have in a simulation ?

Good afternoon everyone,

I run a flat plate simulation, RANS with rhoCentralFoam, with a 600 probes to compute some boundary layer parameters. It was done in parallel processing, and when I reconstructed the fields...there was no fields. And the probes working were not all, only the first 334 probes defined in the controlDict, that is the folder exists but no sub folders with the starting time and fields.

Summarizing, not all the probes worked (and no warnings was given) and I can not view the fields in paraview. And the program runs without any other problem.

Thanks in advance.

I run other simulation with fewer probes, they did not work at all. Some of them do not have all the time steps.

Does anyone know what is the problem ?

I define the probes in the controlDict in the following way (at the bottom of the file):

Code:

functions

(

  probe_number_1

  {

    type probes;

    functionObjectLibs ("libsampling.so");

    region region0;

    probeLocations

    (

      (-0.0100 0.120001 0) 

    );

    fields

    (

      U

    );

  }

)

I must say that in the files where it failed to write the time-steps I can not open the file with gedit.

Hi guilha,

I got your private message. I suspect that the problem might be simpler than you expect: you might be running out of disk space. To check this, run:

Code:

df -h

And check the entry for "/" or "/home" and check how much it's telling you it has got occupied and how much is free.

On the other hand, if disk space isn't the problem, then I need some more information:

Which OpenFOAM version or variant are you using?
Which Linux Distribution are you using?
What installation instructions have you followed for installing OpenFOAM?
How many cells does your mesh have?
How much memory does your machine have?
How many sub-domains are you using?
Are you 100% certain that the mesh has the same geometrical units as the probe locations? In other words, did you open the case in ParaView and placed some "Sphere" sources located at the desired probe locations, to make sure the locations are valid?
Did you check the mesh using checkMesh? A complete check is done like this:

Code:

checkMesh -allGeometry -allTopology
Did you check the contents of the folders "processor*"?
What are the time related settings you are using in "controlDict"? It's possible that you missed some minor-looking detail, which might actually influence the time snapshots that are saved.
It's also possible that the solver, even though it gave no error message, it might actually have indicated that nothing useful was being calculated. Therefore, can you please provide the last time iteration output from the solver?

I ask all of these questions, because the information you provided isn't enough to diagnose the problem ;)

Best regards,
Bruno

Thank you Bruno,

If the problem is the lack of memory, should not it give this error
http://www.cfd-online.com/Forums/ope...-2-errors.html

- my OpenFOAM version is 2.0.1;
- debian
- I do not know, it might be impossible to know (I am on the university computers)
- 3.1 million cells
- 900 gb but only 100 gb available
- I used 32 nodes and 64 too
- I do not know how to use paraView to view the probes, I found a filter with the option of Probe Location but I could not find out anything, but I suppose the problem is not the location
- the checkMesh (with the two options) said the Mesh is OK but it gave an error

Code:

--> FOAM Serious Error : 

    From function IOobject::readHeader(Istream&)

    in file db/IOobject/IOobjectReadHeader.C at line 89

    Reading "/home/guilha/Desktop/resultados/cavidade_LES_130kx24_smagorinsky_perfil_power_law_v3/0.0144/uniform/time" at line 1

    First token could not be read or is not the keyword 'FoamFile'



Check header is of the form:



/*--------------------------------*- C++ -*----------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  2.0.1                                 |

|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |

|    \\/     M anipulation  |                                                 |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    location    "0.0144/uniform";

    object      time;

}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



End

- no I did not, and I erased it to save memory
- my controDict file is (I omitted the probes because I have already put an example)

Code:

/*--------------------------------*- C++ -*----------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  2.1.0                                 |

|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |

|    \\/     M anipulation  |                                                 |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    location    "system";

    object      controlDict;

}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



application     rhoCentralFoam;



startFrom       latestTime;

//startFrom       startTime;



startTime       0;



stopAt          endTime;



endTime         0.02;



deltaT          1.0e-07;



writeControl    runTime;



writeInterval   2.0e-04; // É LES...



purgeWrite      0;



writeFormat     ascii;



writePrecision  7;



writeCompression off;



timeFormat      general;



timePrecision   6;



runTimeModifiable false;



adjustTimeStep  no;



functions

(

);

- the last iteration output was

Code:

Mean and max Courant Numbers = 0.04979834 0.1448724

Time = 0.02



diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0

diagonal:  Solving for rhoUx, Initial residual = 0, Final residual = 0, No Iterations 0

diagonal:  Solving for rhoUy, Initial residual = 0, Final residual = 0, No Iterations 0

diagonal:  Solving for rhoUz, Initial residual = 0, Final residual = 0, No Iterations 0

smoothSolver:  Solving for Ux, Initial residual = 1.374598e-06, Final residual = 4.865261e-15, No Iterations 3

smoothSolver:  Solving for Uy, Initial residual = 3.260119e-06, Final residual = 2.374335e-14, No Iterations 3

smoothSolver:  Solving for Uz, Initial residual = 5.533801e-06, Final residual = 4.280753e-15, No Iterations 3

diagonal:  Solving for rhoE, Initial residual = 0, Final residual = 0, No Iterations 0

smoothSolver:  Solving for e, Initial residual = 5.643462e-06, Final residual = 8.838985e-14, No Iterations 3

ExecutionTime = 54098.04 s  ClockTime = 54515 s



End



Finalising parallel run

In the header of my controlDict file it says that the OpenFOAM version is the 2.1.0 but the OpenFOAM's folder name is openfoam201...

When I run simulations I can only run 24 hours, then the computer kills the run. When I rerun, from the previous saved time, a new folder is built in the probe's folder. It was on one of those folders that it did not wrote on every probes. For instance if my signal is from 0-0.01 from 0.008 to 0.009, in some probes there is very few results.

Edit: I can view the results in paraview.

Hi Guilha,

Quote: