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                    \\     ||  | Multiphase Code Repository by HZDR
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License
    This file is part of the Multiphase Code Repository by HZDR.

    Copyright (C) 2025 by Helmholtz-Zentrum Dresden-Rossendorf e.V. (HZDR),
    Website: https://hzdr.de

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Class
    Foam::dragModels::Coste

Description
    Drag model to estimate the shear induced drag for large-scale and completely
    under-resolved interfaces. The drag coefficient is based on an approximation
    of a common interfacial shear-stress for either side of the interface. Both
    shear boundary layers next to the interface are considered with individual
    wall laws.

    Reference:
    \verbatim
        Coste, P. (2013).
        A Large Interface Model for two-phase CFD.
        Nuclear Engineering and Design, 255, 38–50.
    \endverbatim

Usage
    \table
        Property          | Description              | Required | Default value
        residualDragCoeff | Residual drag coefficient| yes      | -
    \endtable

    Example usage:
    \verbatim
    gas_segregatedWith_liquid
    {
        type                Coste;

        residualDragCoeff   1e-2;
    }
    \endverbatim

See also
    Foam::underResolutionModel

SourceFiles
    Coste.C

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

#ifndef Coste_H
#define Coste_H

#include "dragModel.H"
#include "segregatedPhaseInterface.H"

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

namespace Foam
{
namespace dragModels
{

/*---------------------------------------------------------------------------*\
                            Class Coste Declaration
\*---------------------------------------------------------------------------*/

class Coste
:
    public dragModel
{
    // Private Data

        //- Interface
        const segregatedPhaseInterface interface_;

        //- Value of residual drag
        const dimensionedScalar residualK_;


public:

    //- Runtime type information
    TypeName("Coste");


    // Constructors

        //- Construct from a dictionary and an interface
        Coste
        (
            const dictionary& dict,
            const phaseInterface& interface,
            const bool registerObject
        );


    //- Destructor
    virtual ~Coste();


    // Member Functions

        //- Return the drag coefficient K as a scalar
        //  used in the momentum equations
        //    ddt(alpha1*rho1*U1) + ... = ... K*(U2-U1)
        //    ddt(alpha2*rho2*U2) + ... = ... K*(U1-U2)
        virtual tmp<volScalarField> K() const;

        //- Return the drag coefficient Kf
        //  used in the face-momentum equations
        virtual tmp<surfaceScalarField> Kf() const;
};


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

} // End namespace dragModels
} // End namespace Foam

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

#endif

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