/*---------------------------------------------------------------------------*\
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  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | www.openfoam.com
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-------------------------------------------------------------------------------
    Copyright (C) 2011-2017 OpenFOAM Foundation
    Copyright (C) 2019 OpenCFD Ltd.
-------------------------------------------------------------------------------
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/>.

Class
    Foam::alphaContactAngleTwoPhaseFvPatchScalarField

Group
    grpWallBoundaryConditions grpGenericBoundaryConditions

Description
    Abstract base class for two-phase alphaContactAngle boundary conditions.

    Derived classes must implement the theta() function which returns the
    wall contact angle field.

    The essential entry "limit" controls the gradient of alpha1 on the wall:
      - none - Calculate the gradient from the contact-angle without limiter
      - gradient - Limit the wall-gradient such that alpha1 remains bounded
        on the wall
      - alpha - Bound the calculated alpha1 on the wall
      - zeroGradient - Set the gradient of alpha1 to 0 on the wall, i.e.
        reproduce previous behaviour, the pressure BCs can be left as before.

    Note that if any of the first three options are used the boundary condition
    on \c p_rgh must set to guarantee that the flux is corrected to be zero at
    the wall e.g.:

    \verbatim
    <patchName>
    {
        type            alphaContactAngle;
        limit           none;
    }
    \endverbatim

SourceFiles
    alphaContactAngleTwoPhaseFvPatchScalarField.C

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

#ifndef alphaContactAngleTwoPhaseFvPatchScalarField_H
#define alphaContactAngleTwoPhaseFvPatchScalarField_H

#include "fixedGradientFvPatchFields.H"
#include "fvsPatchFields.H"

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

namespace Foam
{

/*---------------------------------------------------------------------------*\
         Class alphaContactAngleTwoPhaseFvPatchScalarField Declaration
\*---------------------------------------------------------------------------*/

class alphaContactAngleTwoPhaseFvPatchScalarField
:
    public fixedGradientFvPatchScalarField
{
public:

    // Abstract class, no runtime information

    //- Alpha limit options
    enum limitControls
    {
        lcNone,
        lcGradient,
        lcZeroGradient,
        lcAlpha
    };

    static const Enum<limitControls> limitControlNames_;
    limitControls limit_;

    // Constructors

        //- Construct from patch and internal field
        alphaContactAngleTwoPhaseFvPatchScalarField
        (
            const fvPatch&,
            const DimensionedField<scalar, volMesh>&
        );

        //- Construct from patch, internal field and dictionary
        alphaContactAngleTwoPhaseFvPatchScalarField
        (
            const fvPatch&,
            const DimensionedField<scalar, volMesh>&,
            const dictionary&
        );

        //- Construct by mapping onto a new patch
        alphaContactAngleTwoPhaseFvPatchScalarField
        (
            const alphaContactAngleTwoPhaseFvPatchScalarField&,
            const fvPatch&,
            const DimensionedField<scalar, volMesh>&,
            const fvPatchFieldMapper&
        );

        //- Construct as copy
        alphaContactAngleTwoPhaseFvPatchScalarField
        (
            const alphaContactAngleTwoPhaseFvPatchScalarField&
        );

        //- Construct as copy setting internal field reference
        alphaContactAngleTwoPhaseFvPatchScalarField
        (
            const alphaContactAngleTwoPhaseFvPatchScalarField&,
            const DimensionedField<scalar, volMesh>&
        );


    // Member Functions

        //- Return the contact angle
        virtual tmp<scalarField> theta
        (
            const fvPatchVectorField& Up,
            const fvsPatchVectorField& nHat
        ) const = 0;

        //- Evaluate the patch field
        virtual void evaluate
        (
            const Pstream::commsTypes commsType=Pstream::commsTypes::buffered
        );

        //- Write
        virtual void write(Ostream& os) const;


    // Member Operators

        //- Inherit assignment operators
        using fvPatchField<scalar>::operator=;
};


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

} // End namespace Foam

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

#endif

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