/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     |
    \\  /    A nd           | Copyright (C) 1991-2009 OpenCFD Ltd.
     \\/     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 2 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, write to the Free Software Foundation,
    Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Class
    Foam::pressureGradientExplicitSource

Description
    Creates a cell set pressure gradient source

    Note: Currently only handles kinematic pressure

SourceFiles
    pressureGradientExplicitSource.C

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

#ifndef pressureGradientExplicitSource_H
#define pressureGradientExplicitSource_H

#include "autoPtr.H"
#include "topoSetSource.H"
#include "cellSet.H"
#include "fvMesh.H"
#include "volFields.H"

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

namespace Foam
{

/*---------------------------------------------------------------------------*\
              Class pressureGradientExplicitSource Declaration
\*---------------------------------------------------------------------------*/

class pressureGradientExplicitSource
{
    // Private data

        //- Name of the source
        const word sourceName_;

        //- Reference to the mesh
        const fvMesh& mesh_;

        //- Reference to the velocity field
        volVectorField& U_;

        //- Properties dictionary
        IOdictionary dict_;

        //- Average velocity
        vector Ubar_;

        //- Initial pressure gradient
        dimensionedScalar gradPini_;

        //- Pressure gradient
        dimensionedScalar gradP_;

        //- Flow direction
        vector flowDir_;

        //- Name of cell source
        word cellSource_;

        //- The method by which the cells will be selected
        autoPtr<topoSetSource> cellSelector_;

        //- The set of selected cells
        cellSet selectedCellSet_;


    // Private Member Functions

        //- Write the pressure gradient to file (for restarts etc)
        void writeGradP() const;

        //- Disallow default bitwise copy construct
        pressureGradientExplicitSource(const pressureGradientExplicitSource&);

        //- Disallow default bitwise assignment
        void operator=(const pressureGradientExplicitSource&);


public:

    // Constructors

        //- Construct from explicit source name and mesh
        pressureGradientExplicitSource
        (
            const word& sourceName,
            volVectorField& U
        );


    // Member Functions

        // Access

            //- Return a tmp field of the source
            tmp<DimensionedField<vector, volMesh> > Su() const;


        //- Correct driving force for a constant mass flow rate
        void update();
};


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

} // End namespace Foam

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

#endif

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