saturation.hh

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#ifndef DUMUX_FVSATURATION2P_HH
#define DUMUX_FVSATURATION2P_HH
 
#include <dumux/porousmediumflow/2p/sequential/transport/properties.hh>
#include <dumux/porousmediumflow/sequential/cellcentered/transport.hh>
 
namespace Dumux {

template<class TypeTag>
class FVSaturation2P: public FVTransport<TypeTag>
{
    using ParentType = FVTransport<TypeTag>;
    using Implementation = GetPropType<TypeTag, Properties::TransportModel>;
 
    using GridView = typename GetPropType<TypeTag, Properties::GridGeometry>::GridView;
 
    enum
    {
        dim = GridView::dimension, dimWorld = GridView::dimensionworld
    };
 
    using Scalar = GetPropType<TypeTag, Properties::Scalar>;
    using Problem = GetPropType<TypeTag, Properties::Problem>;
 
    using Velocity = GetPropType<TypeTag, Properties::Velocity>;
    using CapillaryFlux = GetPropType<TypeTag, Properties::CapillaryFlux>;
    using GravityFlux = GetPropType<TypeTag, Properties::GravityFlux>;
 
    using SpatialParams = GetPropType<TypeTag, Properties::SpatialParams>;
    using MaterialLaw = typename SpatialParams::MaterialLaw;
 
    using Indices = typename GetPropType<TypeTag, Properties::ModelTraits>::Indices;
 
    using FluidSystem = GetPropType<TypeTag, Properties::FluidSystem>;
    using FluidState = GetPropType<TypeTag, Properties::FluidState>;
 
    using SolutionTypes = GetProp<TypeTag, Properties::SolutionTypes>;
 
    using BoundaryTypes = GetPropType<TypeTag, Properties::BoundaryTypes>;
    using PrimaryVariables = typename SolutionTypes::PrimaryVariables;
 
    using CellData = GetPropType<TypeTag, Properties::CellData>;
 
    enum
    {
        pw = Indices::pressureW,
        pn = Indices::pressureNw,
        pGlobal = Indices::pressureGlobal,
        vw = Indices::velocityW,
        vn = Indices::velocityNw,
        vt = Indices::velocityTotal,
        sw = Indices::saturationW,
        sn = Indices::saturationNw
    };
    enum
    {
        wPhaseIdx = Indices::wPhaseIdx,
        nPhaseIdx = Indices::nPhaseIdx,
        saturationIdx = Indices::saturationIdx,
        satEqIdx = Indices::satEqIdx,
        numPhases = getPropValue<TypeTag, Properties::NumPhases>()
    };
 
    using TransportSolutionType = GetPropType<TypeTag, Properties::TransportSolutionType>;
 
    using Element = typename GridView::Traits::template Codim<0>::Entity;
    using Intersection = typename GridView::Intersection;
 
    using GlobalPosition = Dune::FieldVector<Scalar, dimWorld>;
    using DimVector = Dune::FieldVector<Scalar, dim>;
 
protected:
    CapillaryFlux& capillaryFlux()
    {
        return *capillaryFlux_;
    }
 
    const CapillaryFlux& capillaryFlux() const
    {
        return *capillaryFlux_;
    }
 
    GravityFlux& gravityFlux()
    {
        return *gravityFlux_;
    }
 
    const GravityFlux& gravityFlux() const
    {
        return *gravityFlux_;
    }
 
public:
    Velocity& velocity()
    {
        return *velocity_;
    }
 
    Velocity& velocity() const
    {
        return *velocity_;
    }

    void getFlux(Scalar& update, const Intersection& intersection, CellData& cellDataI);

    void getFluxOnBoundary(Scalar& update, const Intersection& intersection, CellData& cellDataI);

    void getSource(Scalar& update, const Element& element, CellData& cellDataI);

    void initialize();

    void updateMaterialLaws();
 

    void getTransportedQuantity(TransportSolutionType& transportedQuantity)
    {
        int size = problem_.gridView().size(0);
        transportedQuantity.resize(size);
        for (int i = 0; i < size; i++)
        {
            switch (saturationType_)
            {
            case sw:
            {
                transportedQuantity[i] = problem_.variables().cellData(i).saturation(wPhaseIdx);
                break;
            }
            case sn:
            {
                transportedQuantity[i] = problem_.variables().cellData(i).saturation(nPhaseIdx);
                break;
            }
            }
        }
    }

    void setTransportedQuantity(TransportSolutionType& transportedQuantity)
    {
        int size = problem_.gridView().size(0);
        for (int i = 0; i < size; i++)
        {
            CellData& cellData = problem_.variables().cellData(i);
            switch (saturationType_)
            {
            case sw:
            {
                Scalar sat = transportedQuantity[i];
 
                    cellData.setSaturation(wPhaseIdx, sat);
                    cellData.setSaturation(nPhaseIdx, 1 - sat);
                break;
            }
            case sn:
            {
                Scalar sat = transportedQuantity[i];
 
                    cellData.setSaturation(wPhaseIdx,1 -sat);
                    cellData.setSaturation(nPhaseIdx, sat);
                break;
            }
            }
        }
    }

    template<class DataEntry>
    bool inPhysicalRange(DataEntry& entry)
    {
        return (entry > -1e-6 && entry < 1.0 + 1e-6);
    }

    void updateTransportedQuantity(TransportSolutionType& updateVec)
    {
        if (this->enableLocalTimeStepping())
            this->innerUpdate(updateVec);
        else
            asImp_().updateSaturationSolution(updateVec);
    }

    void updateTransportedQuantity(TransportSolutionType& updateVec, Scalar dt)
    {
        asImp_().updateSaturationSolution(updateVec, dt);
    }

    void updateSaturationSolution(TransportSolutionType& updateVec)
    {
        Scalar dt = problem_.timeManager().timeStepSize();
        int size = problem_.gridView().size(0);
        for (int i = 0; i < size; i++)
        {
            asImp_().updateSaturationSolution(i, updateVec[i][0], dt);
        }
    }

    void updateSaturationSolution(TransportSolutionType& updateVec, Scalar dt)
    {
        int size = problem_.gridView().size(0);
        for (int i = 0; i < size; i++)
        {
            asImp_().updateSaturationSolution(i, updateVec[i][0], dt);
        }
    }

    void updateSaturationSolution(int eIdxGlobal, Scalar update, Scalar dt)
    {
        CellData& cellData = problem_.variables().cellData(eIdxGlobal);
 
        switch (saturationType_)
        {
        case sw:
        {
            Scalar sat = cellData.saturation(wPhaseIdx) + dt*update;
 
                cellData.setSaturation(wPhaseIdx, sat);
                cellData.setSaturation(nPhaseIdx, 1 - sat);
            break;
        }
        case sn:
        {
            Scalar sat = cellData.saturation(nPhaseIdx) + dt*update;
 
                cellData.setSaturation(wPhaseIdx,1 -sat);
                cellData.setSaturation(nPhaseIdx, sat);
            break;
        }
        }
    }

    template<class MultiWriter>
    void addOutputVtkFields(MultiWriter &writer)
    {
        int size = problem_.gridView().size(0);
        TransportSolutionType *saturation = writer.allocateManagedBuffer(size);
        TransportSolutionType *saturationSecond = 0;
 
        if (vtkOutputLevel_ > 0)
        {
            saturationSecond = writer.allocateManagedBuffer(size);
        }
 
        for (int i = 0; i < size; i++)
        {
            CellData& cellData = problem_.variables().cellData(i);
 
            if (saturationType_ == sw)
            {
                (*saturation)[i] = cellData.saturation(wPhaseIdx);
                if (vtkOutputLevel_ > 0)
                {
                    (*saturationSecond)[i] = cellData.saturation(nPhaseIdx);
                }
            }
            else if (saturationType_ == sn)
            {
                (*saturation)[i] = cellData.saturation(nPhaseIdx);
                if (vtkOutputLevel_ > 0)
                {
                    (*saturationSecond)[i] = cellData.saturation(wPhaseIdx);
                }
            }
        }
 
        if (saturationType_ == sw)
        {
            writer.attachCellData(*saturation, "wetting saturation");
            if (vtkOutputLevel_ > 0)
            {
                writer.attachCellData(*saturationSecond, "nonwetting saturation");
            }
        }
        else if (saturationType_ == sn)
        {
            writer.attachCellData(*saturation, "nonwetting saturation");
            if (vtkOutputLevel_ > 0)
            {
                writer.attachCellData(*saturationSecond, "wetting saturation");
            }
        }
 
        if (velocity().calculateVelocityInTransport())
        velocity().addOutputVtkFields(writer);
 
        return;
    }

    void serializeEntity(std::ostream &outstream, const Element &element)
    {
        int eIdxGlobal = problem_.variables().index(element);
 
        Scalar sat = 0.0;
        switch (saturationType_)
        {
        case sw:
            sat = problem_.variables().cellData(eIdxGlobal).saturation(wPhaseIdx);
        break;
        case sn:
            sat = problem_.variables().cellData(eIdxGlobal).saturation(nPhaseIdx);
            break;
        }
 
        outstream << sat;
    }

    void deserializeEntity(std::istream &instream, const Element &element)
    {
        int eIdxGlobal = problem_.variables().index(element);
 
        Scalar sat = 0.;
        instream >> sat;
 
        switch (saturationType_)
        {
        case sw:
            problem_.variables().cellData(eIdxGlobal).setSaturation(wPhaseIdx, sat);
            problem_.variables().cellData(eIdxGlobal).setSaturation(nPhaseIdx, 1-sat);
        break;
        case sn:
            problem_.variables().cellData(eIdxGlobal).setSaturation(nPhaseIdx, sat);
            problem_.variables().cellData(eIdxGlobal).setSaturation(wPhaseIdx, 1-sat);
            break;
        }
    }
 

    FVSaturation2P(Problem& problem) :
            ParentType(problem), problem_(problem), threshold_(1e-6),
            switchNormals_(getParam<bool>("Impet.SwitchNormals"))
    {
        if (compressibility_ && velocityType_ == vt)
        {
            DUNE_THROW(Dune::NotImplemented,
                    "Total velocity - global pressure - model cannot be used with compressible fluids!");
        }
        if (saturationType_ != sw && saturationType_ != sn)
        {
            DUNE_THROW(Dune::NotImplemented, "Saturation type not supported!");
        }
        if (pressureType_ != pw && pressureType_ != pn && pressureType_ != pGlobal)
        {
            DUNE_THROW(Dune::NotImplemented, "Pressure type not supported!");
        }
        if (velocityType_ != vw && velocityType_ != vn && velocityType_ != vt)
        {
            DUNE_THROW(Dune::NotImplemented, "Velocity type not supported!");
        }
 
        capillaryFlux_ = std::make_shared<CapillaryFlux>(problem);
        gravityFlux_ = std::make_shared<GravityFlux>(problem);
        velocity_ = std::make_shared<Velocity>(problem);
 
        vtkOutputLevel_ = getParam<int>("Vtk.OutputLevel");
        porosityThreshold_ = getParam<Scalar>("Impet.PorosityThreshold");
    }
 
private:
    Implementation &asImp_()
    { return *static_cast<Implementation *>(this); }

    const Implementation &asImp_() const
    { return *static_cast<const Implementation *>(this); }
 
    Problem& problem_;
    std::shared_ptr<Velocity> velocity_;
    std::shared_ptr<CapillaryFlux> capillaryFlux_;
    std::shared_ptr<GravityFlux> gravityFlux_;
 
    int vtkOutputLevel_;
    Scalar porosityThreshold_;
 
    static const bool compressibility_ = getPropValue<TypeTag, Properties::EnableCompressibility>();
    static const int saturationType_ = getPropValue<TypeTag, Properties::SaturationFormulation>();
    static const int velocityType_ = getPropValue<TypeTag, Properties::VelocityFormulation>();
    static const int pressureType_ = getPropValue<TypeTag, Properties::PressureFormulation>();
 
    Scalar density_[numPhases];
    Scalar viscosity_[numPhases];
 
    const Scalar threshold_;
    const bool switchNormals_;
};

template<class TypeTag>
void FVSaturation2P<TypeTag>::getFlux(Scalar& update, const Intersection& intersection, CellData& cellDataI)
{
    auto elementI = intersection.inside();
    auto elementJ = intersection.outside();
 
    const CellData& cellDataJ = problem_.variables().cellData(problem_.variables().index(elementJ));
 
    // get global coordinates of cell centers
    const GlobalPosition& globalPosI = elementI.geometry().center();
    const GlobalPosition& globalPosJ = elementJ.geometry().center();
 
    // cell volume, assume linear map here
    Scalar volume = elementI.geometry().volume();
    using std::max;
    Scalar porosity = max(problem_.spatialParams().porosity(elementI), porosityThreshold_);
 
    if (compressibility_)
    {
        viscosity_[wPhaseIdx] = cellDataI.viscosity(wPhaseIdx);
        viscosity_[nPhaseIdx] = cellDataI.viscosity(nPhaseIdx);
    }
 
    // local number of faces
    int isIndex = intersection.indexInInside();
 
    GlobalPosition unitOuterNormal = intersection.centerUnitOuterNormal();
    if (switchNormals_)
        unitOuterNormal *= -1.0;
 
    Scalar faceArea = intersection.geometry().volume();
 
    if (velocity().calculateVelocityInTransport() && !cellDataI.fluxData().haveVelocity(isIndex))
        velocity().calculateVelocity(intersection, cellDataI);
 
    //get velocity*normalvector*facearea/(volume*porosity)
    Scalar factorW = (cellDataI.fluxData().velocity(wPhaseIdx, isIndex) * unitOuterNormal) * faceArea;
    Scalar factorNw = (cellDataI.fluxData().velocity(nPhaseIdx, isIndex) * unitOuterNormal) * faceArea;
    Scalar factorTotal = factorW + factorNw;
 
    // distance vector between barycenters
    GlobalPosition distVec = globalPosJ - globalPosI;
    // compute distance between cell centers
    Scalar dist = distVec.two_norm();
 
    bool takeNeighbor = (elementI.level() < elementJ.level());
    //get phase potentials
    bool upwindWI =
            (takeNeighbor) ? !cellDataJ.fluxData().isUpwindCell(wPhaseIdx, intersection.indexInOutside()) :
                    cellDataI.fluxData().isUpwindCell(wPhaseIdx, isIndex);
    bool upwindNwI =
            (takeNeighbor) ? !cellDataJ.fluxData().isUpwindCell(nPhaseIdx, intersection.indexInOutside()) :
                    cellDataI.fluxData().isUpwindCell(nPhaseIdx, isIndex);
 
    Scalar lambdaW = 0;
    Scalar lambdaNw = 0;
 
    //upwinding of lambda dependend on the phase potential gradients
    if (upwindWI)
    {
        lambdaW = cellDataI.mobility(wPhaseIdx);
        if (compressibility_)
        {
            lambdaW /= cellDataI.density(wPhaseIdx);
        } //divide by density because lambda is saved as lambda*density
    }
    else
    {
        lambdaW = cellDataJ.mobility(wPhaseIdx);
        if (compressibility_)
        {
            lambdaW /= cellDataJ.density(wPhaseIdx);
        } //divide by density because lambda is saved as lambda*density
    }
 
    if (upwindNwI)
    {
        lambdaNw = cellDataI.mobility(nPhaseIdx);
        if (compressibility_)
        {
            lambdaNw /= cellDataI.density(nPhaseIdx);
        } //divide by density because lambda is saved as lambda*density
    }
    else
    {
        lambdaNw = cellDataJ.mobility(nPhaseIdx);
        if (compressibility_)
        {
            lambdaNw /= cellDataJ.density(nPhaseIdx);
        } //divide by density because lambda is saved as lambda*density
    }
 
    switch (velocityType_)
    {
    case vt:
    {
        //add cflFlux for time-stepping
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                            viscosity_[nPhaseIdx], factorTotal, intersection);
 
        //determine phase saturations from primary saturation variable
        Scalar satWI = cellDataI.saturation(wPhaseIdx);
        Scalar satWJ = cellDataJ.saturation(wPhaseIdx);
 
        Scalar pcI = cellDataI.capillaryPressure();
        Scalar pcJ = cellDataJ.capillaryPressure();
 
        // calculate the saturation gradient
        GlobalPosition pcGradient = unitOuterNormal;
        pcGradient *= (pcI - pcJ) / dist;
 
        // get the diffusive part
        DimVector flux(0.);
        capillaryFlux().getFlux(flux, intersection, satWI, satWJ, pcGradient);
        Scalar capillaryFlux = (flux * unitOuterNormal * faceArea);
 
        flux = 0.0;
        gravityFlux().getFlux(flux, intersection, satWI, satWJ);
        Scalar gravityFlux =  (flux * unitOuterNormal * faceArea);
 
        switch (saturationType_)
        {
        case sw:
        {
            //vt*fw
            factorTotal *= lambdaW / (lambdaW + lambdaNw);
            break;
        }
        case sn:
        {
            //vt*fn
            factorTotal *= lambdaNw / (lambdaW + lambdaNw);
            capillaryFlux *= -1;
            gravityFlux *= -1;
            break;
        }
        }
        factorTotal -= capillaryFlux;
        factorTotal += gravityFlux;
 
        //add cflFlux for time-stepping
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                            viscosity_[nPhaseIdx], 10 * capillaryFlux, intersection);
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                            viscosity_[nPhaseIdx], 10 * gravityFlux, intersection);
 
        break;
    }
    default:
    {
        if (compressibility_)
        {
            factorW /= cellDataI.density(wPhaseIdx);
            factorNw /= cellDataI.density(nPhaseIdx);
        }
 
        //add cflFlux for time-stepping
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                            viscosity_[nPhaseIdx], factorW, intersection, wPhaseIdx);
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                            viscosity_[nPhaseIdx], factorNw, intersection, nPhaseIdx);
 
        break;
    }
    }
 
    switch (velocityType_)
    {
    case vt:
        update -= factorTotal / (volume * porosity); //-:v>0, if flow leaves the cell
        break;
    default:
        switch (saturationType_)
        {
        case sw:
            update -= factorW / (volume * porosity);//-:v>0, if flow leaves the cell
            break;
        case sn:
            update -= factorNw / (volume * porosity); //-:v>0, if flow leaves the cell
            break;
        }
        break;
    }
}

template<class TypeTag>
void FVSaturation2P<TypeTag>::getFluxOnBoundary(Scalar& update, const Intersection& intersection, CellData& cellDataI)
{
    auto elementI = intersection.inside();
 
    // get global coordinates of cell centers
    const GlobalPosition& globalPosI = elementI.geometry().center();
 
    // center of face in global coordinates
    const GlobalPosition& globalPosJ = intersection.geometry().center();
 
    // cell volume, assume linear map here
    Scalar volume = elementI.geometry().volume();
    using std::max;
    Scalar porosity = max(problem_.spatialParams().porosity(elementI), porosityThreshold_);
 
    if (compressibility_)
    {
        viscosity_[wPhaseIdx] = cellDataI.viscosity(wPhaseIdx);
        viscosity_[nPhaseIdx] = cellDataI.viscosity(nPhaseIdx);
    }
 
    // local number of faces
    int isIndex = intersection.indexInInside();
 
    GlobalPosition unitOuterNormal = intersection.centerUnitOuterNormal();
    if (switchNormals_)
        unitOuterNormal *= -1.0;
 
    Scalar faceArea = intersection.geometry().volume();
 
    if (velocity().calculateVelocityInTransport())
        velocity().calculateVelocityOnBoundary(intersection, cellDataI);
 
    //get velocity*normalvector*facearea/(volume*porosity)
    Scalar factorW = (cellDataI.fluxData().velocity(wPhaseIdx, isIndex) * unitOuterNormal) * faceArea;
    Scalar factorNw = (cellDataI.fluxData().velocity(nPhaseIdx, isIndex) * unitOuterNormal) * faceArea;
    Scalar factorTotal = factorW + factorNw;
 
    // distance vector between barycenters
    GlobalPosition distVec = globalPosJ - globalPosI;
 
    // compute distance between cell centers
    Scalar dist = distVec.two_norm();
 
    //get boundary type
    BoundaryTypes bcType;
    problem_.boundaryTypes(bcType, intersection);
    PrimaryVariables boundValues(0.0);
 
    if (bcType.isDirichlet(satEqIdx))
    {
        problem_.dirichlet(boundValues, intersection);
 
        Scalar satBound = boundValues[saturationIdx];
 
        //determine phase saturations from primary saturation variable
        Scalar satWI = cellDataI.saturation(wPhaseIdx);
        Scalar satWBound = 0;
        switch (saturationType_)
        {
        case sw:
        {
            satWBound = satBound;
            break;
        }
        case sn:
        {
            satWBound = 1 - satBound;
            break;
        }
        }
 
        Scalar pcBound = MaterialLaw::pc(problem_.spatialParams().materialLawParams(elementI), satWBound);
 
        Scalar lambdaW = 0;
        Scalar lambdaNw = 0;
 
        //upwinding of lambda dependend on the phase potential gradients
        if (cellDataI.fluxData().isUpwindCell(wPhaseIdx, isIndex))
        {
            lambdaW = cellDataI.mobility(wPhaseIdx);
            if (compressibility_)
            {
                lambdaW /= cellDataI.density(wPhaseIdx);
            } //divide by density because lambda is saved as lambda*density
        }
        else
        {
            if (compressibility_)
            {
                lambdaW = MaterialLaw::krw(problem_.spatialParams().materialLawParams(elementI), satWBound)
                        / FluidSystem::viscosity(cellDataI.fluidState(), wPhaseIdx);
            }
            else
            {
                lambdaW = MaterialLaw::krw(problem_.spatialParams().materialLawParams(elementI), satWBound)
                        / viscosity_[wPhaseIdx];
            }
        }
 
        if (cellDataI.fluxData().isUpwindCell(nPhaseIdx, isIndex))
        {
            lambdaNw = cellDataI.mobility(nPhaseIdx);
            if (compressibility_)
            {
                lambdaNw /= cellDataI.density(nPhaseIdx);
            } //divide by density because lambda is saved as lambda*density
        }
        else
        {
            if (compressibility_)
            {
                lambdaNw = MaterialLaw::krn(problem_.spatialParams().materialLawParams(elementI), satWBound)
                        / FluidSystem::viscosity(cellDataI.fluidState(), nPhaseIdx);
            }
            else
            {
                lambdaNw = MaterialLaw::krn(problem_.spatialParams().materialLawParams(elementI), satWBound)
                        / viscosity_[nPhaseIdx];
            }
        }
 
        switch (velocityType_)
        {
        case vt:
        {
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorTotal, intersection);
 
            Scalar pcI = cellDataI.capillaryPressure();
 
            // calculate the saturation gradient
            GlobalPosition pcGradient = unitOuterNormal;
            pcGradient *= (pcI - pcBound) / dist;
 
            // get the diffusive part -> give 1-sat because sat = S_n and lambda = lambda(S_w) and pc = pc(S_w)
            DimVector flux(0.);
            capillaryFlux().getFlux(flux, intersection, satWI, satWBound, pcGradient);
            Scalar capillaryFlux = flux * unitOuterNormal * faceArea;
 
            flux = 0.0;
            gravityFlux().getFlux(flux, intersection, satWI, satWBound);
            Scalar gravityFlux = flux * unitOuterNormal * faceArea;
 
            switch (saturationType_)
            {
            case sw:
            {
                //vt*fw
                factorTotal *= lambdaW / (lambdaW + lambdaNw);
                break;
            }
            case sn:
            {
                //vt*fn
                factorTotal *= lambdaNw / (lambdaW + lambdaNw);
                capillaryFlux *= -1; //add cflFlux for time-stepping
                this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                    viscosity_[nPhaseIdx], factorW, intersection, wPhaseIdx);
                this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                    viscosity_[nPhaseIdx], factorNw, intersection, nPhaseIdx);
                gravityFlux *= -1;
                break;
            }
            }
            //vt*fw
            factorTotal -= capillaryFlux;
            factorTotal += gravityFlux;
 
            //add cflFlux for time-stepping
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], 10 * capillaryFlux, intersection);
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], 10 * gravityFlux, intersection);
 
            break;
        }
        default:
        {
            if (compressibility_)
            {
                factorW /= cellDataI.density(wPhaseIdx);
                factorNw /= cellDataI.density(nPhaseIdx);
            }
 
            //add cflFlux for time-stepping
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorW, intersection, wPhaseIdx);
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorNw, intersection, nPhaseIdx);
 
            break;
        }
        }
    } //end dirichlet boundary
 
    if (bcType.isNeumann(satEqIdx))
    {
        problem_.neumann(boundValues, intersection);
        factorW = boundValues[wPhaseIdx];
        factorNw = boundValues[nPhaseIdx];
        factorW *= faceArea;
        factorNw *= faceArea;
 
        //get mobilities
        Scalar lambdaW, lambdaNw;
 
        lambdaW = cellDataI.mobility(wPhaseIdx);
        lambdaNw = cellDataI.mobility(nPhaseIdx);
        if (compressibility_)
        {
            lambdaW /= cellDataI.density(wPhaseIdx);
            lambdaNw /= cellDataI.density(nPhaseIdx);
            factorW /= cellDataI.density(wPhaseIdx);
            factorNw /= cellDataI.density(nPhaseIdx);
        }
        else
        {
            factorW /= density_[wPhaseIdx];
            factorNw /= density_[nPhaseIdx];
        }
 
        switch (velocityType_)
        {
        case vt:
        {
            //add cflFlux for time-stepping
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorW + factorNw, intersection);
            break;
        }
        default:
        {
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorW, intersection, wPhaseIdx);
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorNw, intersection, nPhaseIdx);
 
            break;
        }
        }
 
    } //end neumann boundary
    if (bcType.isOutflow(satEqIdx))
    {
        //get mobilities
        Scalar lambdaW = cellDataI.mobility(wPhaseIdx);
        Scalar lambdaNw = cellDataI.mobility(nPhaseIdx);
        if (compressibility_)
        {
            lambdaW /= cellDataI.density(wPhaseIdx);
            lambdaNw /= cellDataI.density(nPhaseIdx);
        }
 
        if (velocityType_ == vt)
        {
            switch (saturationType_)
            {
            case sw:
            {
                //vt*fw
                factorTotal *= lambdaW / (lambdaW + lambdaNw);
                this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                    viscosity_[nPhaseIdx], factorTotal, intersection);
                break;
            }
            case sn:
            {
                //vt*fn
                factorTotal *= lambdaNw / (lambdaW + lambdaNw);
                this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                    viscosity_[nPhaseIdx], factorTotal, intersection);
                break;
            }
            }
        }
        else
        {
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorW, intersection, wPhaseIdx);
            this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                                viscosity_[nPhaseIdx], factorNw, intersection, nPhaseIdx);
        }
    }
    switch (velocityType_)
    {
    case vt:
        update -= factorTotal / (volume * porosity); //-:v>0, if flow leaves the cell
        break;
    default:
        switch (saturationType_)
        {
        case sw:
            update -= factorW / (volume * porosity); //-:v>0, if flow leaves the cell
            break;
        case sn:
            update -= factorNw / (volume * porosity); //-:v>0, if flow leaves the cell
            break;
        }
        break;
    }
}

template<class TypeTag>
void FVSaturation2P<TypeTag>::getSource(Scalar& update, const Element& element, CellData& cellDataI)
{
    // cell volume, assume linear map here
    Scalar volume = element.geometry().volume();
 
    using std::max;
    Scalar porosity = max(problem_.spatialParams().porosity(element), porosityThreshold_);
 
    if (compressibility_)
    {
        viscosity_[wPhaseIdx] = cellDataI.viscosity(wPhaseIdx);
        viscosity_[nPhaseIdx] = cellDataI.viscosity(nPhaseIdx);
    }
 
    PrimaryVariables sourceVec(0.0);
    problem_.source(sourceVec, element);
 
    if (compressibility_)
    {
        sourceVec[wPhaseIdx] /= cellDataI.density(wPhaseIdx);
        sourceVec[nPhaseIdx] /= cellDataI.density(nPhaseIdx);
    }
    else
    {
        sourceVec[wPhaseIdx] /= density_[wPhaseIdx];
        sourceVec[nPhaseIdx] /= density_[nPhaseIdx];
    }
 
    //get mobilities
    Scalar lambdaW = cellDataI.mobility(wPhaseIdx);
    Scalar lambdaNw = cellDataI.mobility(nPhaseIdx);
    if (compressibility_)
    {
        lambdaW /= cellDataI.density(wPhaseIdx);
        lambdaNw /= cellDataI.density(nPhaseIdx);
    }
 
    switch (saturationType_)
    {
    case sw:
    {
        if (sourceVec[wPhaseIdx] < 0 && cellDataI.saturation(wPhaseIdx) < threshold_)
            sourceVec[wPhaseIdx] = 0.0;
 
        update += sourceVec[wPhaseIdx] / porosity;
        break;
    }
    case sn:
    {
        if (sourceVec[nPhaseIdx] < 0 && cellDataI.saturation(nPhaseIdx) < threshold_)
            sourceVec[nPhaseIdx] = 0.0;
 
        update += sourceVec[nPhaseIdx] / porosity;
        break;
    }
    }
 
    switch (velocityType_)
    {
    case vt:
    {
        //add cflFlux for time-stepping
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx], viscosity_[nPhaseIdx],
                (sourceVec[wPhaseIdx] + sourceVec[nPhaseIdx]) * -1 * volume, element);
        break;
    }
    default:
    {
        //add cflFlux for time-stepping
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                            viscosity_[nPhaseIdx], sourceVec[wPhaseIdx] * -1 * volume, element,
                wPhaseIdx);
        this->evalCflFluxFunction().addFlux(lambdaW, lambdaNw, viscosity_[wPhaseIdx],
                                            viscosity_[nPhaseIdx], sourceVec[nPhaseIdx] * -1 * volume, element,
                nPhaseIdx);
        break;
    }
    }
}

template<class TypeTag>
void FVSaturation2P<TypeTag>::initialize()
{
    ParentType::initialize();
 
    if (!compressibility_)
    {
        const auto element = *problem_.gridView().template begin<0>();
        FluidState fluidState;
        fluidState.setPressure(wPhaseIdx, problem_.referencePressure(element));
        fluidState.setPressure(nPhaseIdx, problem_.referencePressure(element));
        fluidState.setTemperature(problem_.temperature(element));
        fluidState.setSaturation(wPhaseIdx, 1.);
        fluidState.setSaturation(nPhaseIdx, 0.);
        density_[wPhaseIdx] = FluidSystem::density(fluidState, wPhaseIdx);
        density_[nPhaseIdx] = FluidSystem::density(fluidState, nPhaseIdx);
        viscosity_[wPhaseIdx] = FluidSystem::viscosity(fluidState, wPhaseIdx);
        viscosity_[nPhaseIdx] = FluidSystem::viscosity(fluidState, nPhaseIdx);
    }
 
    // iterate through leaf grid an evaluate c0 at cell center
    for (const auto& element : elements(problem_.gridView()))
    {
        PrimaryVariables initSol(0.0);
        problem_.initial(initSol, element);
 
        int eIdxGlobal = problem_.variables().index(element);
 
        CellData& cellData = problem_.variables().cellData(eIdxGlobal);
 
        switch (saturationType_)
        {
        case sw:
        {
                cellData.setSaturation(wPhaseIdx, initSol[saturationIdx]);
                cellData.setSaturation(nPhaseIdx, 1 - initSol[saturationIdx]);
            break;
        }
        case sn:
        {
                cellData.setSaturation(wPhaseIdx,1 -initSol[saturationIdx]);
                cellData.setSaturation(nPhaseIdx, initSol[saturationIdx]);
 
            break;
        }
        }
    }
 
    velocity_->initialize();
    capillaryFlux_->initialize();
    gravityFlux_->initialize();
 
    return;
}

template<class TypeTag>
void FVSaturation2P<TypeTag>::updateMaterialLaws()
{
    // iterate through leaf grid an evaluate c0 at cell center
    for (const auto& element : elements(problem_.gridView()))
    {
        int eIdxGlobal = problem_.variables().index(element);
 
        CellData& cellData = problem_.variables().cellData(eIdxGlobal);
 
        //determine phase saturations from primary saturation variable
        Scalar satW = cellData.saturation(wPhaseIdx);
 
        Scalar pc = MaterialLaw::pc(problem_.spatialParams().materialLawParams(element), satW);
 
        cellData.setCapillaryPressure(pc);
 
        // initialize mobilities
        Scalar mobilityW = MaterialLaw::krw(problem_.spatialParams().materialLawParams(element), satW) / viscosity_[wPhaseIdx];
        Scalar mobilityNw = MaterialLaw::krn(problem_.spatialParams().materialLawParams(element), satW) / viscosity_[nPhaseIdx];
 
        // initialize mobilities
        cellData.setMobility(wPhaseIdx, mobilityW);
        cellData.setMobility(nPhaseIdx, mobilityNw);
 
        //initialize fractional flow functions
        cellData.setFracFlowFunc(wPhaseIdx, mobilityW / (mobilityW + mobilityNw));
        cellData.setFracFlowFunc(nPhaseIdx, mobilityNw / (mobilityW + mobilityNw));
    }
    return;
}
 
} // end namespace Dumux
#endif