BinghamPlastic.C

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    Copyright (C) 2021 OpenCFD Ltd.
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#include "BinghamPlastic.H"
#include "addToRunTimeSelectionTable.H"
#include "fvcGrad.H"

// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //

namespace Foam
{
namespace mixtureViscosityModels
{
    defineTypeNameAndDebug(BinghamPlastic, 0);

    addToRunTimeSelectionTable
    (
        mixtureViscosityModel,
        BinghamPlastic,
        dictionary
    );
}
}


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

Foam::mixtureViscosityModels::BinghamPlastic::BinghamPlastic
(
    const word& name,
    const dictionary& viscosityProperties,
    const volVectorField& U,
    const surfaceScalarField& phi
)
:
    plastic(name, viscosityProperties, U, phi, typeName),
    yieldStressCoeff_
    (
        "BinghamCoeff",
        dimensionSet(1, -1, -2, 0, 0),
        plasticCoeffs_
    ),
    yieldStressExponent_
    (
        "BinghamExponent",
        dimless,
        plasticCoeffs_
    ),
    yieldStressOffset_
    (
        "BinghamOffset",
        dimless,
        plasticCoeffs_
    ),
    U_(U)
{}


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

Foam::tmp<Foam::volScalarField>
Foam::mixtureViscosityModels::BinghamPlastic::mu
(
    const volScalarField& muc
) const
{
    volScalarField tauy
    (
        yieldStressCoeff_
       *(
            pow
            (
                scalar(10),
                yieldStressExponent_
               *(max(alpha_, scalar(0)) + yieldStressOffset_)
            )
          - pow
            (
                scalar(10),
                yieldStressExponent_*yieldStressOffset_
            )
        )
    );

    volScalarField mup(plastic::mu(muc));

    dimensionedScalar tauySmall("tauySmall", tauy.dimensions(), SMALL);

    return min
    (
        tauy
       /(
            sqrt(2.0)*mag(symm(fvc::grad(U_)))
          + 1.0e-4*(tauy + tauySmall)/mup
        )
      + mup,
        muMax_
    );
}


bool Foam::mixtureViscosityModels::BinghamPlastic::read
(
    const dictionary& viscosityProperties
)
{
    plastic::read(viscosityProperties);

    plasticCoeffs_.readEntry("BinghamCoeff", yieldStressCoeff_);
    plasticCoeffs_.readEntry("BinghamExponent", yieldStressExponent_);
    plasticCoeffs_.readEntry("BinghamOffset", yieldStressOffset_);

    return true;
}


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