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what is the purpose of rhoMin and rhoMax in fvsolution

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Old   June 29, 2012, 10:09
Default what is the purpose of rhoMin and rhoMax in fvsolution
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Mihai Pruna
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I noticed the simulation aborts if the limits are breached, but why are units specified there as well?
rhoMin rhoMin [1 -3 0 0 0] 0.01;
rhoMax rhoMax [1 -3 0 0 0] 100.0;
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Old   June 30, 2012, 07:12
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Bruno Santos
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Hi Mihai,

The units are probably supplied for the sake of completeness, while also making it easier to access when reading the dictionary file.
This way it's not necessary to first read the value to a "scalar" variable and then add dimensions by creating a "dimensionedScalar" based on the first one. These dimensions are necessary for field operations, since the "rho" field has dimensions itself.

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Bruno
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Old   July 2, 2012, 09:06
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Mihai Pruna
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I think I understand. Is it because rho is derived?
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Old   July 2, 2012, 09:19
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Example: https://github.com/OpenFOAM/OpenFOAM...createFields.H

Code:
autoPtr<basicPsiThermo> pThermo
    (
        basicPsiThermo::New(mesh)
    );
    basicPsiThermo& thermo = pThermo();

    volScalarField rho
    (
        IOobject
        (
            "rho",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        thermo.rho()
    );

//....

    dimensionedScalar rhoMax(simple.dict().lookup("rhoMax"));
    dimensionedScalar rhoMin(simple.dict().lookup("rhoMin"));
As you can see, this makes it easier to read from the dictionary file. As for the "rho" field, it's initialized with the "basicPsiThermo" based structure... which I'll leave to you as an exercise: http://foam.sourceforge.net/docs/cpp/index.html

edit: forgot to mention: rho is used here: https://github.com/OpenFOAM/OpenFOAM...pleFoam/pEqn.H

Last edited by wyldckat; July 2, 2012 at 09:20. Reason: see "edit:"
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