thixotropicViscosity.C

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    Copyright (C) 2013-2017 OpenFOAM Foundation
    Copyright (C) 2023 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.

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#include "thixotropicViscosity.H"
#include "kinematicSingleLayer.H"
#include "addToRunTimeSelectionTable.H"

#include "fvmDdt.H"
#include "fvmDiv.H"
#include "fvcDiv.H"
#include "fvmSup.H"

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

namespace Foam
{
namespace regionModels
{
namespace surfaceFilmModels
{

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

defineTypeNameAndDebug(thixotropicViscosity, 0);

addToRunTimeSelectionTable
(
    filmViscosityModel,
    thixotropicViscosity,
    dictionary
);


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

thixotropicViscosity::thixotropicViscosity
(
    surfaceFilmRegionModel& film,
    const dictionary& dict,
    volScalarField& mu
)
:
    filmViscosityModel(typeName, film, dict, mu),
    a_("a", dimless/dimTime, coeffDict_),
    b_("b", dimless, coeffDict_),
    d_("d", dimless, coeffDict_),
    c_("c", pow(dimTime, d_.value() - scalar(1)), coeffDict_),
    mu0_("mu0", dimPressure*dimTime, coeffDict_),
    muInf_("muInf", mu0_.dimensions(), coeffDict_),
    K_(1 - sqrt(muInf_/mu0_)),
    lambda_
    (
        IOobject
        (
            IOobject::scopedName(typeName, "lambda"),
            film.regionMesh().time().timeName(),
            film.regionMesh().thisDb(),
            IOobject::MUST_READ,
            IOobject::AUTO_WRITE,
            IOobject::REGISTER
        ),
        film.regionMesh()
    )
{
    lambda_.clamp_range(zero_one{});

    // Initialise viscosity to inf value because it cannot be evaluated yet
    mu_ = muInf_;
    mu_.correctBoundaryConditions();
}


// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //

thixotropicViscosity::~thixotropicViscosity()
{}


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

void thixotropicViscosity::correct
(
    const volScalarField& p,
    const volScalarField& T
)
{
    const kinematicSingleLayer& film = filmType<kinematicSingleLayer>();

    const volVectorField& U = film.U();
    const volVectorField& Uw = film.Uw();
    const volScalarField& delta = film.delta();
    const volScalarField& deltaRho = film.deltaRho();
    const surfaceScalarField& phi = film.phi();
    const volScalarField& alpha = film.alpha();
    const Time& runTime = this->film().regionMesh().time();

    // Shear rate
    const volScalarField gDot
    (
        "gDot",
        alpha*mag(U - Uw)/(delta + film.deltaSmall())
    );

    if (debug && runTime.writeTime())
    {
        gDot.write();
    }

    const dimensionedScalar deltaRho0
    (
        "deltaRho0",
        deltaRho.dimensions(),
        ROOTVSMALL
    );

    const surfaceScalarField phiU(phi/fvc::interpolate(deltaRho + deltaRho0));

    const dimensionedScalar c0("c0", dimless/dimTime, ROOTVSMALL);
    const volScalarField coeff("coeff", -c_*pow(gDot, d_) + c0);

    fvScalarMatrix lambdaEqn
    (
        fvm::ddt(lambda_)
      + fvm::div(phiU, lambda_)
      - fvm::Sp(fvc::div(phiU), lambda_)
      ==
        a_*pow((1 - lambda_), b_)
      + fvm::SuSp(coeff, lambda_)

        // Include the effect of the impinging droplets added with lambda = 0
      - fvm::Sp
        (
            max
            (
               -film.rhoSp(),
                dimensionedScalar(film.rhoSp().dimensions(), Zero)
            )/(deltaRho + deltaRho0),
            lambda_
        )
    );

    lambdaEqn.relax();
    lambdaEqn.solve();

    lambda_.clamp_range(zero_one{});

    mu_ = muInf_/(sqr(1 - K_*lambda_) + ROOTVSMALL);
    mu_.correctBoundaryConditions();
}


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

} // End namespace surfaceFilmModels
} // End namespace regionModels
} // End namespace Foam

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