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========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Copyright (C) 2011-2026 OpenFOAM Foundation
\\/ M anipulation |
-------------------------------------------------------------------------------
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.
OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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::XiModel
Description
Base-class for all Xi models used by the b-Xi combustion model
References:
\verbatim
Weller, H. G. (1993).
The development of a new flame area combustion model
using conditional averaging.
Thermo-fluids section report TF 9307.
Weller, H. G., Tabor, G., Gosman, A. D., & Fureby, C. (1998, January).
Application of a flame-wrinkling LES combustion model
to a turbulent mixing layer.
In Symposium (International) on combustion
(Vol. 27, No. 1, pp. 899-907). Elsevier.
\endverbatim
Xi is given through an algebraic expression (Foam::XiModels::algebraic), by
solving a transport equation (Foam::XiModels::transport.H) or a fixed value
(Foam::XiModels::fixed).
In the algebraic and transport methods \f$\Xi_{eq}\f$ is calculated in
similar way. In the algebraic approach, \f$\Xi_{eq}\f$ is the value used in
the \f$ b \f$ transport equation.
\f$\Xi_{eq}\f$ is calculated as follows:
\f$\Xi_{eq} = 1 + (1 + 2\Xi_{coeff}(0.5 - \dwea{b}))(\Xi^* - 1)\f$
where:
\f$ \dwea{b} \f$ is the regress variable.
\f$ \Xi_{coeff} \f$ is a model constant.
\f$ \Xi^* \f$ is the total equilibrium wrinkling combining the effects
of the flame instability and turbulence interaction and is given by
\f[
\Xi^* = \frac {R}{R - G_\eta - G_{in}}
\f]
where:
\f$ G_\eta \f$ is the generation rate of wrinkling due to turbulence
interaction.
\f$ G_{in} = \kappa \rho_{u}/\rho_{b} \f$ is the generation
rate due to the flame instability.
By adding the removal rates of the two effects:
\f[
R = G_\eta \frac{\Xi_{\eta_{eq}}}{\Xi_{\eta_{eq}} - 1}
+ G_{in} \frac{\Xi_{{in}_{eq}}}{\Xi_{{in}_{eq}} - 1}
\f]
where:
\f$ R \f$ is the total removal.
\f$ G_\eta \f$ is a model constant.
\f$ \Xi_{\eta_{eq}} \f$ is the flame wrinkling due to turbulence.
\f$ \Xi_{{in}_{eq}} \f$ is the equilibrium level of the flame wrinkling
generated by instability. It is a constant (default 2.5).
SourceFiles
XiModel.C
\*---------------------------------------------------------------------------*/
#ifndef XiModel_H
#define XiModel_H
#include "ubRhoThermo.H"
#include "compressibleMomentumTransportModels.H"
#include "runTimeSelectionTables.H"
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
namespace Foam
{
/*---------------------------------------------------------------------------*\
Class XiModel Declaration
\*---------------------------------------------------------------------------*/
class XiModel
{
protected:
// Protected data
//- Thermo
const ubRhoThermo& thermo_;
//- Turbulence
const compressibleMomentumTransportModel& momentumTransport_;
const volScalarField& Su_;
const volScalarField& rho_;
const volScalarField& b_;
//- Flame wrinkling field
volScalarField Xi_;
// Protected Member Functions
//- Update coefficients from given dictionary
virtual bool readCoeffs(const dictionary& dict) = 0;
public:
//- Runtime type information
TypeName("XiModel");
// Declare run-time constructor selection table
declareRunTimeSelectionTable
(
autoPtr,
XiModel,
dictionary,
(
const dictionary& dict,
const ubRhoThermo& thermo,
const compressibleMomentumTransportModel& turbulence,
const volScalarField& Su
),
(
dict,
thermo,
turbulence,
Su
)
);
// Constructors
//- Construct from components
XiModel
(
const ubRhoThermo& thermo,
const compressibleMomentumTransportModel& turbulence,
const volScalarField& Su
);
//- Disallow default bitwise copy construction
XiModel(const XiModel&) = delete;
// Selectors
//- Return a reference to the selected Xi model
static autoPtr<XiModel> New
(
const dictionary& combustionProperties,
const ubRhoThermo& thermo,
const compressibleMomentumTransportModel& momentumTransport,
const volScalarField& Su
);
//- Destructor
virtual ~XiModel();
// Member Functions
//- Return the flame-wrinkling Xi
virtual const volScalarField& Xi() const
{
return Xi_;
}
//- Return the flame diffusivity
virtual tmp<volScalarField> Db() const = 0;
//- Add Xi to the multivariateSurfaceInterpolationScheme table
// if required
virtual void addXi
(
multivariateSurfaceInterpolationScheme<scalar>::fieldTable&
)
{}
//- Reset Xi to the unburnt state (1)
virtual void reset();
//- Correct the flame-wrinkling Xi
virtual void correct() = 0;
//- Update properties from the given combustionProperties dictionary
bool read(const dictionary& combustionProperties);
// Member Operators
//- Disallow default bitwise assignment
void operator=(const XiModel&) = delete;
};
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
} // End namespace Foam
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
#endif
// ************************************************************************* //
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