BirdCarreau.H

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License
    This file is part of OpenFOAM.
 
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    the Free Software Foundation, either version 3 of the License, or
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Class
    Foam::laminarModels::generalisedNewtonianViscosityModels::BirdCarreau
 
Description
    Bird-Carreau generalised Newtonian viscosity model
 
    The Bird-Carreau-Yasuda form is also supported if the optional \c a
    coefficient is specified.  \c a defaults to 2 for the Bird-Carreau model.
 
    The coefficient applied to strain rate \f$\gamma\f$ can be specified either
    as the constant \c k or the critical stress level at the transition to
    shear thinning \c tauStar if \c tauStar is provided:
 
    Kinematic viscosity [m^2/s]
 
    \f[
        \nu = \nu_\infty\,
            + (\nu_0 - \nu_\infty)\,
              \left(1 + (k\gamma)^a \right)^{(n - 1)/a}
    \f]
 
    or
 
    \f[
        \nu = \nu_\infty
            + (\nu_0 - \nu_\infty)
              \left(1 + (\frac{\nu_0\gamma}{\tau^*} )^a \right)^{(n - 1)/a}
    \f]
 
    Example specification for a paint using the first form of the model:
    \verbatim
         viscosityModel BirdCarreau;
 
         nuInf       1e-5;
         k           10;
         n           0.5;
    \endverbatim
 
    Example specification for a polymer using the second form of the model:
    \verbatim
         viscosityModel BirdCarreau;
 
         nuInf       0;
         tauStar     90;
         n           0.5;
    \endverbatim
 
    Note the viscosity \c nu0 at zero strain rate is a physical property,
    generally specified in the physicalProperties file.
 
SourceFiles
    BirdCarreau.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef BirdCarreau_H
#define BirdCarreau_H
 
#include "strainRateViscosityModel.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
namespace laminarModels
{
namespace generalisedNewtonianViscosityModels
{
 
/*---------------------------------------------------------------------------*\
                         Class BirdCarreau Declaration
\*---------------------------------------------------------------------------*/
 
class BirdCarreau
:
    public strainRateViscosityModel
{
    // Private Data
 
        dimensionedScalar nuInf_;
        dimensionedScalar k_;
        dimensionedScalar tauStar_;
        dimensionedScalar n_;
        dimensionedScalar a_;
 
 
public:
 
    //- Runtime type information
    TypeName("BirdCarreau");
 
 
    // Constructors
 
        //- Construct from components
        BirdCarreau
        (
            const dictionary& viscosityProperties,
            const Foam::viscosity& viscosity,
            const volVectorField& U
        );
 
 
    //- Destructor
    virtual ~BirdCarreau()
    {}
 
 
    // Member Functions
 
        //- Read transportProperties dictionary
        virtual bool read(const dictionary& viscosityProperties);
 
        //- Return the laminar viscosity
        virtual tmp<volScalarField> nu
        (
            const volScalarField& nu0,
            const volScalarField& strainRate
        ) const;
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace generalisedNewtonianViscosityModels
} // End namespace laminarModels
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //