/*---------------------------------------------------------------------------*\
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                    \\     ||  | Multiphase Code Repository by HZDR
  ======   //   ||  || ===//   | Website: https://doi.org/10.14278/rodare.767
  ||  ||  //    ||  // || \\   | License: GPL-3.0-or-later
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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::linearDrag

Description
    Numerical drag model that returns a constant drag coefficient, independent
    from relative velocity. Therefore this numerical drag model behaves
    linearly.

Interfacial momentum transfer due to drag
\f[
    \vec{M}_d = -\vec{M}_c = K\,\left(\vec{U}_c-\vec{U}_d\right)
\f]

Dragfunction K
\f[
    K = \alpha_d Ki
\f]

Usage
    \table
        Parameter   | Name  | Description       | Default value
        \f$Ki\f$    | Ki    | drag coefficient  | -
    \endtable

SourceFiles
    linearDrag.C

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

#ifndef linearDrag_H
#define linearDrag_H

#include "dispersedDragModel.H"

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

namespace Foam
{
namespace dragModels
{

/*---------------------------------------------------------------------------*\
                         Class linearDrag Declaration
\*---------------------------------------------------------------------------*/

class linearDrag
:
    public dispersedDragModel
{
    // Private Data

        //- Drag coefficient
        const dimensionedScalar ki_;

public:

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


    // Constructors

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


    //- Destructor
    virtual ~linearDrag();


    // Member Functions

        //- Drag coefficient
        virtual tmp<volScalarField> CdRe() const;

        //- Return the phase-intensive drag coefficient Ki
        //  used in the momentum equations
        virtual tmp<volScalarField> Ki() const;
};


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

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

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

#endif

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