/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 2011 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/>.

\*---------------------------------------------------------------------------*/

#include "multiphaseSystem.H"
#include "alphaContactAngleFvPatchScalarField.H"
#include "Time.H"
#include "subCycle.H"
#include "MULES.H"
#include "fvcSnGrad.H"
#include "fvcFlux.H"

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

const Foam::scalar Foam::multiphaseSystem::convertToRad =
    Foam::constant::mathematical::pi/180.0;


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

void Foam::multiphaseSystem::calcAlphas()
{
    scalar level = 0.0;
    alphas_ == 0.0;

    forAllIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        alphas_ += level*iter();
        level += 1.0;
    }

    alphas_.correctBoundaryConditions();
}


void Foam::multiphaseSystem::solveAlphas()
{
    word alphaScheme("div(phi,alpha)");
    word alpharScheme("div(phirb,alpha)");

    surfaceScalarField phic(mag(phi_/mesh_.magSf()));

    PtrList<surfaceScalarField> phiAlphaCorrs(phases_.size());
    int phasei = 0;

    forAllIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        phaseModel& phase1 = iter();

        phase1.phiAlpha() =
            dimensionedScalar("0", dimensionSet(0, 3, -1, 0, 0), 0);

        phiAlphaCorrs.set
        (
            phasei,
            new surfaceScalarField
            (
                fvc::flux
                (
                    phi_,
                    phase1,
                    alphaScheme
                )
            )
        );

        surfaceScalarField& phiAlphaCorr = phiAlphaCorrs[phasei];

        forAllIter(PtrDictionary<phaseModel>, phases_, iter2)
        {
            phaseModel& phase2 = iter2();

            if (&phase2 == &phase1) continue;

            surfaceScalarField phir
            (
                (phase1.phi() - phase2.phi())
              + min(cAlpha(phase1, phase2)*phic, max(phic))
               *nHatf(phase1, phase2)
            );

            phiAlphaCorr += fvc::flux
            (
                -fvc::flux(-phir, phase2, alpharScheme),
                phase1,
                alpharScheme
            );
        }

        MULES::limit
        (
            geometricOneField(),
            phase1,
            phi_,
            phiAlphaCorr,
            zeroField(),
            zeroField(),
            1,
            0,
            3,
            true
        );

        phasei++;
    }

    MULES::limitSum(phiAlphaCorrs);

    volScalarField sumAlpha
    (
        IOobject
        (
            "sumAlpha",
            mesh_.time().timeName(),
            mesh_
        ),
        mesh_,
        dimensionedScalar("sumAlpha", dimless, 0)
    );

    phasei = 0;

    forAllIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        phaseModel& phase1 = iter();

        surfaceScalarField& phiAlpha = phiAlphaCorrs[phasei];
        phiAlpha += upwind<scalar>(mesh_, phi_).flux(phase1);

        MULES::explicitSolve
        (
            geometricOneField(),
            phase1,
            phiAlpha,
            zeroField(),
            zeroField()
        );

        phase1.phiAlpha() += phiAlpha;

        Info<< phase1.name() << " volume fraction, min, max = "
            << phase1.weightedAverage(mesh_.V()).value()
            << ' ' << min(phase1).value()
            << ' ' << max(phase1).value()
            << endl;

        sumAlpha += phase1;

        phasei++;
    }

    Info<< "Phase-sum volume fraction, min, max = "
        << sumAlpha.weightedAverage(mesh_.V()).value()
        << ' ' << min(sumAlpha).value()
        << ' ' << max(sumAlpha).value()
        << endl;

    calcAlphas();
}


Foam::dimensionedScalar Foam::multiphaseSystem::sigma
(
    const phaseModel& phase1,
    const phaseModel& phase2
) const
{
    scalarCoeffTable::const_iterator sigma
    (
        sigmas_.find(interfacePair(phase1, phase2))
    );

    if (sigma == sigmas_.end())
    {
        FatalErrorIn
        (
            "multiphaseSystem::sigma(const phaseModel& phase1,"
            "const phaseModel& phase2) const"
        )   << "Cannot find interface " << interfacePair(phase1, phase2)
            << " in list of sigma values"
            << exit(FatalError);
    }

    return dimensionedScalar("sigma", dimSigma_, sigma());
}


Foam::scalar Foam::multiphaseSystem::cAlpha
(
    const phaseModel& phase1,
    const phaseModel& phase2
) const
{
    scalarCoeffTable::const_iterator cAlpha
    (
        cAlphas_.find(interfacePair(phase1, phase2))
    );

    if (cAlpha == cAlphas_.end())
    {
        FatalErrorIn
        (
            "multiphaseSystem::cAlpha"
            "(const phaseModel& phase1, const phaseModel& phase2) const"
        )   << "Cannot find interface " << interfacePair(phase1, phase2)
            << " in list of cAlpha values"
            << exit(FatalError);
    }

    return cAlpha();
}


Foam::dimensionedScalar Foam::multiphaseSystem::Cvm
(
    const phaseModel& phase1,
    const phaseModel& phase2
) const
{
    scalarCoeffTable::const_iterator Cvm
    (
        Cvms_.find(interfacePair(phase1, phase2))
    );

    if (Cvm != Cvms_.end())
    {
        return Cvm()*phase2.rho();
    }

    Cvm = Cvms_.find(interfacePair(phase2, phase1));

    if (Cvm != Cvms_.end())
    {
        return Cvm()*phase1.rho();
    }

    FatalErrorIn
    (
        "multiphaseSystem::sigma"
        "(const phaseModel& phase1, const phaseModel& phase2) const"
    )   << "Cannot find interface " << interfacePair(phase1, phase2)
        << " in list of sigma values"
        << exit(FatalError);

    return Cvm()*phase2.rho();
}


Foam::tmp<Foam::surfaceVectorField> Foam::multiphaseSystem::nHatfv
(
    const volScalarField& alpha1,
    const volScalarField& alpha2
) const
{
    /*
    // Cell gradient of alpha
    volVectorField gradAlpha =
        alpha2*fvc::grad(alpha1) - alpha1*fvc::grad(alpha2);

    // Interpolated face-gradient of alpha
    surfaceVectorField gradAlphaf = fvc::interpolate(gradAlpha);
    */

    surfaceVectorField gradAlphaf
    (
        fvc::interpolate(alpha2)*fvc::interpolate(fvc::grad(alpha1))
      - fvc::interpolate(alpha1)*fvc::interpolate(fvc::grad(alpha2))
    );

    // Face unit interface normal
    return gradAlphaf/(mag(gradAlphaf) + deltaN_);
}


Foam::tmp<Foam::surfaceScalarField> Foam::multiphaseSystem::nHatf
(
    const volScalarField& alpha1,
    const volScalarField& alpha2
) const
{
    // Face unit interface normal flux
    return nHatfv(alpha1, alpha2) & mesh_.Sf();
}


// 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::multiphaseSystem::correctContactAngle
(
    const phaseModel& phase1,
    const phaseModel& phase2,
    surfaceVectorField::GeometricBoundaryField& nHatb
) const
{
    const volScalarField::GeometricBoundaryField& gbf
        = phase1.boundaryField();

    const fvBoundaryMesh& boundary = mesh_.boundary();

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

            vectorField& nHatPatch = nHatb[patchi];

            vectorField AfHatPatch
            (
                mesh_.Sf().boundaryField()[patchi]
               /mesh_.magSf().boundaryField()[patchi]
            );

            alphaContactAngleFvPatchScalarField::thetaPropsTable::
                const_iterator tp =
                acap.thetaProps().find(interfacePair(phase1, phase2));

            if (tp == acap.thetaProps().end())
            {
                FatalErrorIn
                (
                    "multiphaseSystem::correctContactAngle"
                    "(const phaseModel& phase1, const phaseModel& phase2, "
                    "fvPatchVectorFieldField& nHatb) const"
                )   << "Cannot find interface " << interfacePair(phase1, phase2)
                    << "\n    in table of theta properties for patch "
                    << acap.patch().name()
                    << exit(FatalError);
            }

            bool matched = (tp.key().first() == phase1.name());

            scalar theta0 = convertToRad*tp().theta0(matched);
            scalarField theta(boundary[patchi].size(), theta0);

            scalar uTheta = tp().uTheta();

            // Calculate the dynamic contact angle if required
            if (uTheta > SMALL)
            {
                scalar thetaA = convertToRad*tp().thetaA(matched);
                scalar thetaR = convertToRad*tp().thetaR(matched);

                // Calculated the component of the velocity parallel to the wall
                vectorField Uwall
                (
                    phase1.U().boundaryField()[patchi].patchInternalField()
                  - phase1.U().boundaryField()[patchi]
                );
                Uwall -= (AfHatPatch & Uwall)*AfHatPatch;

                // Find the direction of the interface parallel to the wall
                vectorField nWall
                (
                    nHatPatch - (AfHatPatch & nHatPatch)*AfHatPatch
                );

                // Normalise nWall
                nWall /= (mag(nWall) + SMALL);

                // Calculate Uwall resolved normal to the interface parallel to
                // the interface
                scalarField uwall(nWall & Uwall);

                theta += (thetaA - thetaR)*tanh(uwall/uTheta);
            }


            // Reset nHatPatch to correspond to the contact angle

            scalarField a12(nHatPatch & AfHatPatch);

            scalarField b1(cos(theta));

            scalarField b2(nHatPatch.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);

            nHatPatch = a*AfHatPatch + b*nHatPatch;

            nHatPatch /= (mag(nHatPatch) + deltaN_.value());
        }
    }
}


Foam::tmp<Foam::volScalarField> Foam::multiphaseSystem::K
(
    const phaseModel& phase1,
    const phaseModel& phase2
) const
{
    tmp<surfaceVectorField> tnHatfv = nHatfv(phase1, phase2);

    correctContactAngle(phase1, phase2, tnHatfv().boundaryField());

    // Simple expression for curvature
    return -fvc::div(tnHatfv & mesh_.Sf());
}


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

Foam::multiphaseSystem::multiphaseSystem
(
    const fvMesh& mesh,
    const surfaceScalarField& phi
)
:
    IOdictionary
    (
        IOobject
        (
            "transportProperties",
            mesh.time().constant(),
            mesh,
            IOobject::MUST_READ_IF_MODIFIED,
            IOobject::NO_WRITE
        )
    ),
    phases_(lookup("phases"), phaseModel::iNew(mesh)),

    mesh_(mesh),
    phi_(phi),

    alphas_
    (
        IOobject
        (
            "alphas",
            mesh_.time().timeName(),
            mesh_,
            IOobject::NO_READ,
            IOobject::AUTO_WRITE
        ),
        mesh_,
        dimensionedScalar("alphas", dimless, 0.0),
        zeroGradientFvPatchScalarField::typeName
    ),

    sigmas_(lookup("sigmas")),
    dimSigma_(1, 0, -2, 0, 0),
    cAlphas_(lookup("interfaceCompression")),
    Cvms_(lookup("virtualMass")),
    deltaN_
    (
        "deltaN",
        1e-8/pow(average(mesh_.V()), 1.0/3.0)
    )
{
    calcAlphas();
    alphas_.write();

    forAllIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        phaseModelTable_.add(iter());
    }

    interfaceDictTable dragModelsDict(lookup("drag"));

    forAllConstIter(interfaceDictTable, dragModelsDict, iter)
    {
        dragModels_.insert
        (
            iter.key(),
            dragModel::New
            (
                iter(),
                *phaseModelTable_.find(iter.key().first())(),
                *phaseModelTable_.find(iter.key().second())()
            ).ptr()
        );
    }
}


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


Foam::tmp<Foam::volScalarField> Foam::multiphaseSystem::rho() const
{
    PtrDictionary<phaseModel>::const_iterator iter = phases_.begin();

    tmp<volScalarField> trho = iter()*iter().rho();

    for (++iter; iter != phases_.end(); ++iter)
    {
        trho() += iter()*iter().rho();
    }

    return trho;
}


Foam::tmp<Foam::volScalarField> Foam::multiphaseSystem::Cvm
(
    const phaseModel& phase
) const
{
    tmp<volScalarField> tCvm
    (
        new volScalarField
        (
            IOobject
            (
                "Cvm",
                mesh_.time().timeName(),
                mesh_
            ),
            mesh_,
            dimensionedScalar
            (
                "Cvm",
                dimensionSet(1, -3, 0, 0, 0),
                0
            )
        )
    );

    forAllConstIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        const phaseModel& phase2 = iter();

        if (&phase2 != &phase)
        {
            tCvm() += Cvm(phase, phase2)*phase2;
        }
    }

    return tCvm;
}


Foam::tmp<Foam::volVectorField> Foam::multiphaseSystem::Svm
(
    const phaseModel& phase
) const
{
    tmp<volVectorField> tSvm
    (
        new volVectorField
        (
            IOobject
            (
                "Svm",
                mesh_.time().timeName(),
                mesh_
            ),
            mesh_,
            dimensionedVector
            (
                "Svm",
                dimensionSet(1, -2, -2, 0, 0),
                vector::zero
            )
        )
    );

    forAllConstIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        const phaseModel& phase2 = iter();

        if (&phase2 != &phase)
        {
            tSvm() += Cvm(phase, phase2)*phase2*phase2.DDtU();
        }
    }

    return tSvm;
}


Foam::autoPtr<Foam::multiphaseSystem::dragCoeffFields>
Foam::multiphaseSystem::dragCoeffs() const
{
    autoPtr<dragCoeffFields> dragCoeffsPtr(new dragCoeffFields);

    forAllConstIter(dragModelTable, dragModels_, iter)
    {
        const dragModel& dm = *iter();

        dragCoeffsPtr().insert
        (
            iter.key(),
            (
                dm.phase1()*dm.phase2()
               *dm.K(mag(dm.phase1().U() - dm.phase2().U()))
              + dm.residualDrag()
            ).ptr()
        );
    }

    return dragCoeffsPtr;
}


Foam::tmp<Foam::volScalarField> Foam::multiphaseSystem::dragCoeff
(
    const phaseModel& phase,
    const dragCoeffFields& dragCoeffs
) const
{
    tmp<volScalarField> tdragCoeff
    (
        new volScalarField
        (
            IOobject
            (
                "dragCoeff",
                mesh_.time().timeName(),
                mesh_
            ),
            mesh_,
            dimensionedScalar
            (
                "dragCoeff",
                dimensionSet(1, -3, -1, 0, 0),
                0
            )
        )
    );

    dragModelTable::const_iterator dmIter = dragModels_.begin();
    dragCoeffFields::const_iterator dcIter = dragCoeffs.begin();
    for
    (
        ;
        dmIter != dragModels_.end() && dcIter != dragCoeffs.end();
        ++dmIter, ++dcIter
    )
    {
        if
        (
            &phase == &dmIter()->phase1()
         || &phase == &dmIter()->phase2()
        )
        {
            tdragCoeff() += *dcIter();
        }
    }

    return tdragCoeff;
}


Foam::tmp<Foam::surfaceScalarField>
Foam::multiphaseSystem::surfaceTensionForce() const
{
    tmp<surfaceScalarField> tstf
    (
        new surfaceScalarField
        (
            IOobject
            (
                "surfaceTensionForce",
                mesh_.time().timeName(),
                mesh_
            ),
            mesh_,
            dimensionedScalar
            (
                "surfaceTensionForce",
                dimensionSet(1, -2, -2, 0, 0),
                0.0
            )
        )
    );

    surfaceScalarField& stf = tstf();

    forAllConstIter(PtrDictionary<phaseModel>, phases_, iter1)
    {
        const phaseModel& phase1 = iter1();

        PtrDictionary<phaseModel>::const_iterator iter2 = iter1;
        ++iter2;

        for (; iter2 != phases_.end(); ++iter2)
        {
            const phaseModel& phase2 = iter2();

            stf += sigma(phase1, phase2)
               *fvc::interpolate(K(phase1, phase2))*
                (
                    fvc::interpolate(phase2)*fvc::snGrad(phase1)
                  - fvc::interpolate(phase1)*fvc::snGrad(phase2)
                );
        }
    }

    return tstf;
}


Foam::tmp<Foam::volScalarField>
Foam::multiphaseSystem::nearInterface() const
{
    tmp<volScalarField> tnearInt
    (
        new volScalarField
        (
            IOobject
            (
                "nearInterface",
                mesh_.time().timeName(),
                mesh_
            ),
            mesh_,
            dimensionedScalar("nearInterface", dimless, 0.0)
        )
    );

    forAllConstIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        tnearInt() = max(tnearInt(), pos(iter() - 0.01)*pos(0.99 - iter()));
    }

    return tnearInt;
}


void Foam::multiphaseSystem::solve()
{
    forAllIter(PtrDictionary<phaseModel>, phases_, iter)
    {
        iter().correct();
    }

    const Time& runTime = mesh_.time();

    const dictionary& pimpleDict = mesh_.solutionDict().subDict("PIMPLE");

    label nAlphaSubCycles(readLabel(pimpleDict.lookup("nAlphaSubCycles")));

    volScalarField& alpha = phases_.first();

    if (nAlphaSubCycles > 1)
    {
        dimensionedScalar totalDeltaT = runTime.deltaT();

        for
        (
            subCycle<volScalarField> alphaSubCycle(alpha, nAlphaSubCycles);
            !(++alphaSubCycle).end();
        )
        {
            solveAlphas();
        }
    }
    else
    {
        solveAlphas();
    }
}


bool Foam::multiphaseSystem::read()
{
    if (regIOobject::read())
    {
        bool readOK = true;

        PtrList<entry> phaseData(lookup("phases"));
        label phasei = 0;

        forAllIter(PtrDictionary<phaseModel>, phases_, iter)
        {
            readOK &= iter().read(phaseData[phasei++].dict());
        }

        lookup("sigmas") >> sigmas_;
        lookup("interfaceCompression") >> cAlphas_;
        lookup("virtualMass") >> Cvms_;

        return readOK;
    }
    else
    {
        return false;
    }
}


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