XiFluid.H

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Class
    Foam::solvers::XiFluid
 
Description
    Solver module for compressible premixed/partially-premixed combustion with
    turbulence modelling.
 
    Combusting RANS code using the b-Xi two-equation model.
    Xi may be obtained by either the solution of the Xi transport
    equation or from an algebraic expression.  Both approaches are
    based on Gulder's flame speed correlation which has been shown
    to be appropriate by comparison with the results from the
    spectral model.
 
    Strain effects are encorporated directly into the Xi equation
    but not in the algebraic approximation.  Further work need to be
    done on this issue, particularly regarding the enhanced removal rate
    caused by flame compression.  Analysis using results of the spectral
    model will be required.
 
    For cases involving very lean Propane flames or other flames which are
    very strain-sensitive, a transport equation for the laminar flame
    speed is present.  This equation is derived using heuristic arguments
    involving the strain time scale and the strain-rate at extinction.
    the transport velocity is the same as that for the Xi equation.
 
    Uses the flexible PIMPLE (PISO-SIMPLE) solution for time-resolved and
    pseudo-transient and steady simulations.
 
    Optional fvModels and fvConstraints are provided to enhance the simulation
    in many ways including adding various sources, chemical reactions,
    combustion, Lagrangian particles, radiation, surface film etc. and
    constraining or limiting the solution.
 
    Reference:
    \verbatim
        Greenshields, C. J., & Weller, H. G. (2022).
        Notes on Computational Fluid Dynamics: General Principles.
        CFD Direct Ltd.: Reading, UK.
    \endverbatim
 
SourceFiles
    XiFluid.C
 
See also
    Foam::solvers::fluidSolver
    Foam::solvers::isothermalFluid
 
\*---------------------------------------------------------------------------*/
 
#ifndef XiFluid_H
#define XiFluid_H
 
#include "isothermalFluid.H"
#include "psiuMulticomponentThermo.H"
#include "RASThermophysicalTransportModel.H"
#include "unityLewisEddyDiffusivity.H"
#include "laminarFlameSpeed.H"
#include "ignition.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
namespace solvers
{
 
/*---------------------------------------------------------------------------*\
                          Class XiFluid Declaration
\*---------------------------------------------------------------------------*/
 
class XiFluid
:
    public isothermalFluid
{
 
protected:
 
    // Thermophysical properties
 
        psiuMulticomponentThermo& thermo_;
 
 
    // Composition
 
        //- Reference to the combustion mixture
        basicCombustionMixture& composition;
 
        //- Reference to the combustion regress variable
        //  obtained from the combustion mixture
        volScalarField& b_;
 
        //- Set of fields used for the multivariate convection scheme
        multivariateSurfaceInterpolationScheme<scalar>::fieldTable fields;
 
 
    // Reactions
 
        //- Laminar flame-speed model
        autoPtr<laminarFlameSpeed> unstrainedLaminarFlameSpeed;
 
        //- Laminar flame-speed field
        volScalarField Su;
 
        //- Minimum laminar flame-speed allowed for numerical stability
        dimensionedScalar SuMin;
 
        //- Maximum laminar flame-speed allowed for numerical stability
        dimensionedScalar SuMax;
 
        //- Flame wrinkling coefficient field
        volScalarField Xi_;
 
        //- Turbulent flame-speed field
        volScalarField St;
 
        //- Dictionary of combustion model coefficients
        IOdictionary combustionProperties;
 
        //- Name of the strained laminar flame-speed model
        word SuModel;
 
        //- Laminar flame extinction strain-rate
        dimensionedScalar sigmaExt;
 
        //- Name of the flame wrinkling model
        word XiModel;
 
        //- Flame wrinkling model coefficient
        dimensionedScalar XiCoef;
 
        //- Flame wrinkling model shape coefficient
        dimensionedScalar XiShapeCoef;
 
        //- Flame wrinkling model u' coefficient
        dimensionedScalar uPrimeCoef;
 
        //- Ignition model
        ignition ign;
 
 
    // Thermophysical transport
 
        turbulenceThermophysicalTransportModels::unityLewisEddyDiffusivity
        <
            RASThermophysicalTransportModel
            <
                ThermophysicalTransportModel
                <
                    compressibleMomentumTransportModel,
                    fluidThermo
                >
            >
        > thermophysicalTransport;
 
 
    // Protected member functions
 
        //- Solve the ft equation for partially-premixed mixtures
        void ftSolve
        (
            const fv::convectionScheme<scalar>& mvConvection
        );
 
        //- Calculate and return the turbulent flame-speed kernel correction
        dimensionedScalar StCorr
        (
            const volScalarField& c,
            const surfaceScalarField& nf,
            const dimensionedScalar& dMgb
        ) const;
 
        //- Solve the Xi and regress variable equations
        void bSolve
        (
            const fv::convectionScheme<scalar>& mvConvection
        );
 
        //- Solve the unburnt energy equation
        void EauSolve
        (
            const fv::convectionScheme<scalar>& mvConvection
        );
 
        //- Solve the energy equation
        void EaSolve
        (
            const fv::convectionScheme<scalar>& mvConvection
        );
 
 
public:
 
        //- Reference to the fluid thermophysical properties
        const psiuMulticomponentThermo& thermo;
 
        //- Reference to the combustion regress variable
        //  obtained from the combustion mixture
        const volScalarField& b;
 
        //- Flame wrinkling coefficient field
        const volScalarField& Xi;
 
 
    //- Runtime type information
    TypeName("XiFluid");
 
 
    // Constructors
 
        //- Construct from region mesh
        XiFluid(fvMesh& mesh);
 
        //- Disallow default bitwise copy construction
        XiFluid(const XiFluid&) = delete;
 
 
    //- Destructor
    virtual ~XiFluid();
 
 
    // Member Functions
 
        //- Called at the start of the PIMPLE loop
        virtual void prePredictor();
 
        //- Construct and solve the energy equation,
        //  convert to temperature
        //  and update thermophysical and transport properties
        virtual void thermophysicalPredictor();
 
        //- Correct the momentum and thermophysical transport modelling
        virtual void postCorrector();
 
 
    // Member Operators
 
        //- Disallow default bitwise assignment
        void operator=(const XiFluid&) = delete;
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace solvers
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //