Gamma.H

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/*---------------------------------------------------------------------------*\
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  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
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-------------------------------------------------------------------------------
    Copyright (C) 2016-2017 Wikki 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.
 
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    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::GammaWeight
 
Description
    Class with operator() which returns the weighting factors for the
    Gamma differencing scheme.  Used in conjunction with the template class
    NVDscheme.
 
SourceFiles
    GammaMake.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef Gamma_H
#define Gamma_H
 
#include "scalar.H"
#include "vector.H"
#include "Istream.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                           Class GammaWeight Declaration
\*---------------------------------------------------------------------------*/
 
class GammaWeight
{
    scalar k_;
 
public:
 
    GammaWeight(Istream& is)
    :
        k_(readScalar(is))
    {
        if (k_ < 0 || k_ > 1)
        {
            FatalIOErrorInFunction(is)
                << "coefficient = " << k_
                << " should be >= 0 and <= 1"
                << exit(FatalIOError);
        }
 
        // Rescale k_ to be >= 0 and <= 0.5 (TVD conformant)
        // and avoid the /0 when k_ = 0
        k_ = max(k_/2.0, SMALL);
    }
 
 
    scalar weight
    (
        scalar cdWeight,
        scalar faceFlux,
        scalar phiP,
        scalar phiN,
        const vector& gradcP,
        const vector& gradcN,
        const vector& d
    ) const
    {
        scalar magd = mag(d);
        vector dHat = d/mag(d);
 
        scalar gradf = (phiN - phiP)/magd;
 
        scalar gradcf;
        scalar udWeight;
 
        if (faceFlux > 0)
        {
            gradcf = dHat & gradcP;
            udWeight = 1;
        }
        else
        {
            gradcf = dHat & gradcN;
            udWeight = 0;
        }
 
        // Stabilise for division
        gradcf = stabilise(gradcf, SMALL);
 
        scalar phict = 1 - 0.5*gradf/gradcf;
        scalar limiter = min(max(phict/k_, 0), 1);
 
        return limiter*cdWeight + (1 - limiter)*udWeight;
    }
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //