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

    Multiphase Code Repository by HZDR is based on the free software for
    computational fluid dynamics (CFD) from the OpenFOAM Foundation.
    Copyright (C) 2025 by OpenFOAM Foundation, Website: https://openfoam.org

    If you are interested in which files are original OpenFOAM Foundation
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    Multiphase Code Repository by HZDR is free software: you can redistribute
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\*---------------------------------------------------------------------------*/

#include "cipsaMultiphaseEuler.H"
#include "fvcDdt.H"
#include "fvmSup.H"

// * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * * //

void Foam::solvers::cipsaMultiphaseEuler::updateDdtUEqn()
{
    forAll(movingPhases, movingPhasei)
    {
        const phaseModel& phase = movingPhases[movingPhasei];
        const volScalarField& alpha = phase;
        const volScalarField& rhoAlpha = phase.rho();
        const volVectorField& UAlpha = phase.URef();

        ddtUEqns.set
        (
            phase.index(),
            fvm::ddt(alpha, rhoAlpha, UAlpha)
          - fvm::Sp(fvc::ddt(alpha, rhoAlpha), UAlpha)
        );

        word ddtScheme
        (
            mesh.schemes().ddt
            (
                "ddt("
            + alpha.name()
            + ',' + rhoAlpha.name() + ','
            + UAlpha.name() + ')'
            ).last().wordToken()
        );

        if (ddtScheme == "Euler")
        {
            ddtPhiCoeffs.set
            (
                phase.index(),
                (
                    byDt
                    (
                        fvc::interpolate(alpha.oldTime())
                       *fvc::interpolate(rhoAlpha.oldTime())
                       *MRF.absolute(phase.phi()().oldTime())
                    )
                )
            );
        }
        else
        {
            FatalErrorInFunction
                << "Only Euler is an allowed time scheme "
                << "for this solver." << exit(FatalError);
        }
    }
}


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