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Previous: Description of turbulence model Up: Turbulence Modeling in OpenFOAM Next: Example of creating new

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View of the source code of turbulence model

  • Take a look at the two equation turbulence model $ k-\epsilon$ for incompressible fluid flow

     

  • Source code can be found in:

    $FOAM_SRC/TurbulenceModels/turbulenceModels/RAS/kEpsilon

     

  • In file kEpsilon.H there is defined class of $ k-\epsilon$ turbulence model and headers of class functions

     

  • In file kEpsilon.C the model itself is defined

     

  • Let us have a look at the file:

    # less $FOAM_SRC/TurbulenceModels/turbulenceModels/RAS/kEpsilon/kEpsilon.C

     

    /*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2011-2017 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

\*---------------------------------------------------------------------------*/
  • OpenFOAM header

     

    #include "kEpsilon.H"
#include "fvOptions.H"
#include "bound.H"

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
  • Include of header files

     

    namespace Foam
{
namespace RASModels
{

     

  • Entering namespaces Foam, RASModels

     

    // * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //

template<class BasicTurbulenceModel>
void kEpsilon<BasicTurbulenceModel>::correctNut()
{
    this->nut_ = Cmu_*sqr(k_)/epsilon_;
    this->nut_.correctBoundaryConditions();
    fv::options::New(this->mesh_).correct(this->nut_);

    BasicTurbulenceModel::correctNut();
}


template<class BasicTurbulenceModel>
tmp<fvScalarMatrix> kEpsilon<BasicTurbulenceModel>::kSource() const
{
    return tmp<fvScalarMatrix>
    (
        new fvScalarMatrix
        (
            k_,
            dimVolume*this->rho_.dimensions()*k_.dimensions()
            /dimTime
        )
    );
}


template<class BasicTurbulenceModel>
tmp<fvScalarMatrix> kEpsilon<BasicTurbulenceModel>::epsilonSource() const
{
    return tmp<fvScalarMatrix>
    (
        new fvScalarMatrix
        (
            epsilon_,
            dimVolume*this->rho_.dimensions()*epsilon_.dimensions()
            /dimTime
        )
    );
}


// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //

template<class BasicTurbulenceModel>
kEpsilon<BasicTurbulenceModel>::kEpsilon
(
    const alphaField& alpha,
    const rhoField& rho,
    const volVectorField& U,
    const surfaceScalarField& alphaRhoPhi,
    const surfaceScalarField& phi,
    const transportModel& transport,
    const word& propertiesName,
    const word& type
)
:
    eddyViscosity<RASModel<BasicTurbulenceModel>>
    (
        type,
        alpha,
        rho,
        U,
        alphaRhoPhi,
        phi,
        transport,
        propertiesName
    ),

    Cmu_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "Cmu",
            this->coeffDict_,
            0.09
        )
    ),
    C1_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "C1",
            this->coeffDict_,
            1.44
        )
    ),
    C2_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "C2",
            this->coeffDict_,
            1.92
        )
    ),
    C3_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "C3",
            this->coeffDict_,
            0
        )
    ),
    sigmak_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "sigmak",
            this->coeffDict_,
            1.0
        )
    ),
    sigmaEps_
    (
        dimensioned<scalar>::lookupOrAddToDict
        (
            "sigmaEps",
            this->coeffDict_,
            1.3
        )
    ),

    k_
    (
        IOobject
        (
            IOobject::groupName("k", U.group()),
            this->runTime_.timeName(),
            this->mesh_,
            IOobject::MUST_READ,
            IOobject::AUTO_WRITE
        ),
        this->mesh_
    ),
    epsilon_
    (
        IOobject
        (
            IOobject::groupName("epsilon", U.group()),
            this->runTime_.timeName(),
            this->mesh_,
            IOobject::MUST_READ,
            IOobject::AUTO_WRITE
        ),
        this->mesh_
    )
{
    bound(k_, this->kMin_);
    bound(epsilon_, this->epsilonMin_);

    if (type == typeName)
    {
        this->printCoeffs(type);
    }
}

     

  • Class $ k-\epsilon$ constructor
  • Constant definition
  • Definition of eddy viscosity
  • Reading of turbulent quantities

     

    // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

template<class BasicTurbulenceModel>
bool kEpsilon<BasicTurbulenceModel>::read()
{
    if (eddyViscosity<RASModel<BasicTurbulenceModel>>::read())
    {
        Cmu_.readIfPresent(this->coeffDict());
        C1_.readIfPresent(this->coeffDict());
        C2_.readIfPresent(this->coeffDict());
        C3_.readIfPresent(this->coeffDict());
        sigmak_.readIfPresent(this->coeffDict());
        sigmaEps_.readIfPresent(this->coeffDict());

        return true;
    }
    else
    {
        return false;
    }
}

     

  • Function read() reads model constants from turbulenceProperties

     

  • If coefficients not present in turbulenceProperties default coefficients are used

     

    template<class BasicTurbulenceModel>
void kEpsilon<BasicTurbulenceModel>::correct()
{
    if (!this->turbulence_)
    {
        return;
    }

    // Local references
    const alphaField& alpha = this->alpha_;
    const rhoField& rho = this->rho_;
    const surfaceScalarField& alphaRhoPhi = this->alphaRhoPhi_;
    const volVectorField& U = this->U_;
    volScalarField& nut = this->nut_;
    fv::options& fvOptions(fv::options::New(this->mesh_));

    eddyViscosity<RASModel<BasicTurbulenceModel>>::correct();

    volScalarField::Internal divU
    (
        fvc::div(fvc::absolute(this->phi(), U))().v()
    );

    tmp<volTensorField> tgradU = fvc::grad(U);
    volScalarField::Internal G
    (
        this->GName(),
        nut.v()*(dev(twoSymm(tgradU().v())) && tgradU().v())
    );
    tgradU.clear();

    // Update epsilon and G at the wall
    epsilon_.boundaryFieldRef().updateCoeffs();

    // Dissipation equation
    tmp<fvScalarMatrix> epsEqn
    (
        fvm::ddt(alpha, rho, epsilon_)
      + fvm::div(alphaRhoPhi, epsilon_)
      - fvm::laplacian(alpha*rho*DepsilonEff(), epsilon_)
     ==
        C1_*alpha()*rho()*G*epsilon_()/k_()
      - fvm::SuSp(((2.0/3.0)*C1_ - C3_)*alpha()*rho()*divU, epsilon_)
      - fvm::Sp(C2_*alpha()*rho()*epsilon_()/k_(), epsilon_)
      + epsilonSource()
      + fvOptions(alpha, rho, epsilon_)
    );

    epsEqn.ref().relax();
    fvOptions.constrain(epsEqn.ref());
    epsEqn.ref().boundaryManipulate(epsilon_.boundaryFieldRef());
    solve(epsEqn);
    fvOptions.correct(epsilon_);
    bound(epsilon_, this->epsilonMin_);

    // Turbulent kinetic energy equation
    tmp<fvScalarMatrix> kEqn
    (
        fvm::ddt(alpha, rho, k_)
      + fvm::div(alphaRhoPhi, k_)
      - fvm::laplacian(alpha*rho*DkEff(), k_)
     ==
        alpha()*rho()*G
      - fvm::SuSp((2.0/3.0)*alpha()*rho()*divU, k_)
      - fvm::Sp(alpha()*rho()*epsilon_()/k_(), k_)
      + kSource()
      + fvOptions(alpha, rho, k_)
    );

    kEqn.ref().relax();
    fvOptions.constrain(kEqn.ref());
    solve(kEqn);
    fvOptions.correct(k_);
    bound(k_, this->kMin_);

    correctNut();
}
  • Function correct() solves differential equations of model:
  • $ G$ is production of turbulence
  • Equation for rate of dissipation of turbulent kinetic energy $ \epsilon$

     

    $\displaystyle \frac{\partial \epsilon}{\partial t} + u_{j} \sum_{j=1}^{3} \frac{\partial \epsilon}{\partial x_{j}} - \sum_{j=1}^{3} \frac{\partial}{\partial x_{j}} \left[ \left(\alpha_{\epsilon} \nu_{t} + \nu \right) \frac{\partial \epsilon}{\partial x_{j}} \right] = + C_{1\epsilon} \frac{\epsilon}{k} G - C_{2} \frac{\epsilon^{2}}{k}$(24.1)

     

     

  • Equation for turbulent kinetic energy $ k$:

     

    $\displaystyle \frac{\partial k}{\partial t} + u_{j} \sum_{j=1}^{3} \frac{\partial k}{\partial x_{j}} - \sum_{j=1}^{3} \frac{\partial}{\partial x_{j}} \left[ \left(\alpha_{k} \nu_{t} + \nu \right) \frac{\partial k}{\partial x_{j}} \right] = G - \epsilon$(24.2)

     

     

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

} // End namespace RASModels
} // End namespace Foam

// ************************************************************************* //
  • Closing namespaces
  •  
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Previous: Description of turbulence model Up: Turbulence Modeling in OpenFOAM Next: Example of creating new

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