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Turbulent quantities

  • Turbulence parameters are set in file turbulenceProperties in directory constant
  • Print the file on the screen:
    # cat $FOAM_RUN /pitzDaily/constant/turbulenceProperties
    /*--------------------------------*- C++ -*----------------------------------*\
    | =========                 |                                                 |
    | \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
    |  \\    /   O peration     | Version:  dev                                   |
    |   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
    |    \\/     M anipulation  |                                                 |
    \*---------------------------------------------------------------------------*/
    FoamFile
    {
        version     2.0;
        format      ascii;
        class       dictionary;
        location    "constant";
        object      turbulenceProperties;
    }
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    
    simulationType RAS;
    
    RAS
    {
        // Tested with kEpsilon, realizableKE, kOmega, kOmegaSST, v2f,
        // ShihQuadraticKE, LienCubicKE.
        RASModel        kEpsilon;
    
        turbulence      on;
    
        printCoeffs     on;
    }
    
    
    // ************************************************************************* //
    

     

  • Parameter symulationType sets RAS, which stands for Reynolds averaged Navier-Stokes.
  • RAS subdictionary sums up all necessary settings for RAS.
  • RASModel is set to $ k-\epsilon$. Other possibilities are summed up in the commentary.
  • Parameter turbulence can switch turbulence on or off (on/off )
  • Parameter printCoeffs means the turbulence model coefficients are to be printed in standard output to the screen, when solver starts

     

    Selecting RAS turbulence model kEpsilon
    RAS
    {
        RASModel        kEpsilon;
        turbulence      on;
        printCoeffs     on;
        Cmu             0.09;
        C1              1.44;
        C2              1.92;
        C3              0;
        sigmak          1;
        sigmaEps        1.3;
    }
    
  • Parameter kEpsilonCoeffs is optional, and can change default turbulence model coefficients
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Potential of a homogeneous gravitational field

A homogeneous gravitational field is characterized by a constant vector field $ \color{white} \vec{g}$, the well known gravitational acceleration. Let us consider some volume or vessel filled with an incompressible fluid of density $ \color{white} \varrho$. The gravitational field exerts a force on the fluid. Its force density $ \color{white} \vec{f}$ is given by the following well known formula
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It is a simple task to  potential to ([*]). Let us remind, a potential (if it exists) of some given force field $ \color{white} \vec{F}$ is defined as a certain function $ \color{white} \phi$ satisfying the following equation

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We can see that to the $ \color{white} \vec{f}$ given by ([*]) there exists a potential, let us denote it by $ \color{white} \varphi$, stating
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where $ \color{white} C \in \mathbb{R}$ is a constant of integration3.3 and $ \color{white} \vec{r}$ is a position vector3.4.