interfaceProperties.C

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License
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#include "interfaceProperties.H"
#include <twoPhaseInterfaceProperties/alphaContactAngleFvPatchScalarField.H>
#include <OpenFOAM/mathematicalConstants.H>
#include <finiteVolume/surfaceInterpolate.H>
#include <finiteVolume/fvcDiv.H>
#include <finiteVolume/fvcGrad.H>
#include <finiteVolume/fvcSnGrad.H>

// * * * * * * * * * * * * * * * Static Member Data  * * * * * * * * * * * * //

const Foam::scalar Foam::interfaceProperties::convertToRad =
    Foam::mathematicalConstant::pi/180.0;


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

// Correction for the boundary condition on the unit normal nHat on
// walls to produce the correct contact angle.

// The dynamic contact angle is calculated from the component of the
// velocity on the direction of the interface, parallel to the wall.

void Foam::interfaceProperties::correctContactAngle
(
    surfaceVectorField::GeometricBoundaryField& nHatb,
    surfaceVectorField::GeometricBoundaryField& gradAlphaf
) const
{
    const fvMesh& mesh = alpha1_.mesh();
    const volScalarField::GeometricBoundaryField& abf = alpha1_.boundaryField();

    const fvBoundaryMesh& boundary = mesh.boundary();

    forAll(boundary, patchi)
    {
        if (isA<alphaContactAngleFvPatchScalarField>(abf[patchi]))
        {
            alphaContactAngleFvPatchScalarField& acap =
                const_cast<alphaContactAngleFvPatchScalarField&>
                (
                    refCast<const alphaContactAngleFvPatchScalarField>
                    (
                        abf[patchi]
                    )
                );

            fvsPatchVectorField& nHatp = nHatb[patchi];
            scalarField theta =
                convertToRad*acap.theta(U_.boundaryField()[patchi], nHatp);

            vectorField nf = boundary[patchi].nf();

            // Reset nHatp to correspond to the contact angle

            scalarField a12 = nHatp & nf;

            scalarField b1 = cos(theta);

            scalarField b2(nHatp.size());

            forAll(b2, facei)
            {
                b2[facei] = cos(acos(a12[facei]) - theta[facei]);
            }

            scalarField det = 1.0 - a12*a12;

            scalarField a = (b1 - a12*b2)/det;
            scalarField b = (b2 - a12*b1)/det;

            nHatp = a*nf + b*nHatp;

            nHatp /= (mag(nHatp) + deltaN_.value());

            acap.gradient() = (nf & nHatp)*mag(gradAlphaf[patchi]);
            acap.evaluate();
        }
    }
}


void Foam::interfaceProperties::calculateK()
{
    const fvMesh& mesh = alpha1_.mesh();
    const surfaceVectorField& Sf = mesh.Sf();

    // Cell gradient of alpha
    volVectorField gradAlpha = fvc::grad(alpha1_);

    // Interpolated face-gradient of alpha
    surfaceVectorField gradAlphaf = fvc::interpolate(gradAlpha);
    //gradAlphaf -=
    //    (mesh.Sf()/mesh.magSf())
    //   *(fvc::snGrad(alpha1_) - (mesh.Sf() & gradAlphaf)/mesh.magSf());

    // Face unit interface normal
    surfaceVectorField nHatfv = gradAlphaf/(mag(gradAlphaf) + deltaN_);
    correctContactAngle(nHatfv.boundaryField(), gradAlphaf.boundaryField());

    // Face unit interface normal flux
    nHatf_ = nHatfv & Sf;

    // Simple expression for curvature
    K_ = -fvc::div(nHatf_);

    // Complex expression for curvature.
    // Correction is formally zero but numerically non-zero.
    /*
    volVectorField nHat = gradAlpha/(mag(gradAlpha) + deltaN_);
    forAll(nHat.boundaryField(), patchi)
    {
        nHat.boundaryField()[patchi] = nHatfv.boundaryField()[patchi];
    }

    K_ = -fvc::div(nHatf_) + (nHat & fvc::grad(nHatfv) & nHat);
    */
}


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

Foam::interfaceProperties::interfaceProperties
(
    const volScalarField& alpha1,
    const volVectorField& U,
    const IOdictionary& dict
)
:
    transportPropertiesDict_(dict),
    cAlpha_
    (
        readScalar
        (
            alpha1.mesh().solutionDict().subDict("PISO").lookup("cAlpha")
        )
    ),
    sigma_(dict.lookup("sigma")),

    deltaN_
    (
        "deltaN",
        1e-8/pow(average(alpha1.mesh().V()), 1.0/3.0)
    ),

    alpha1_(alpha1),
    U_(U),

    nHatf_
    (
        IOobject
        (
            "nHatf",
            alpha1_.time().timeName(),
            alpha1_.mesh()
        ),
        alpha1_.mesh(),
        dimensionedScalar("nHatf", dimArea, 0.0)
    ),

    K_
    (
        IOobject
        (
            "Kcond",
            alpha1_.time().timeName(),
            alpha1_.mesh()
        ),
        alpha1_.mesh(),
        dimensionedScalar("Kcond", dimless/dimLength, 0.0)
    )
{
    calculateK();
}


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