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Continuity. Stop critertion of PISO and SIMPLE in OpenFOAM solvers.

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Old   September 20, 2010, 16:12
Default Continuity. Stop critertion of PISO and SIMPLE in OpenFOAM solvers.
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Claus Meister
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Hallo Foamers!

I have a question related to OpenFOAM solvers with SIMPLE or PISO loop. Why was as stop criterion the number of iteration used or implemented,respectively, and not a number of accuracy, e.g. 1e-10 (sum,global,cumulative)? Has this a specific reason?

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Old   September 20, 2010, 17:53
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Niklas Nordin
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Quote:
Originally Posted by idrama View Post
Why was as stop criterion the number of iteration used or implemented,respectively, and not a number of accuracy, e.g. 1e-10 (sum,global,cumulative)?
Where?

Do you know you can add an option to the SIMPLE dictionary in system/fvSolution
convergence 1.0e-5;
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Old   September 21, 2010, 03:15
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I did not know that! Honestly, I am a bit surprised. How can I set up such criterion? In guides and documents, I have nothing read about this, anywhere! Where I can find it?
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Old   September 21, 2010, 03:50
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if you are using simpleFoam it is already there, so you just have to add it to the SIMPLE dictionary.

Code:
SIMPLE
{
    nNonOrthogonalCorrectors 1;
    convergence              1.0e-8;
}
a good place to start would be the source code of the application you are using (in this case simpleFoam)
where you will find initConvergenceCheck.H

Code:
// initialize values for convergence checks

    scalar eqnResidual = 1, maxResidual = 0;
    scalar convergenceCriterion = 0;

    simple.readIfPresent("convergence", convergenceCriterion);
so you see that convergence is set to 0 if you dont define it.

and then the convergenceCheck.H which is the last include of the iteration-loop

Code:
// check convergence

if (maxResidual < convergenceCriterion)
{
    Info<< "reached convergence criterion: " << convergenceCriterion << endl;
    runTime.writeAndEnd();
    Info<< "latestTime = " << runTime.timeName() << endl;
}
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Old   September 21, 2010, 04:26
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Thank you for you posted. I will looking for it!
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