lambdaThixotropic.H

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Class
    Foam::laminarModels::lambdaThixotropic
 
Description
    Thixotropic viscosity momentum transport model based on the evolution of
    the structural parameter \f$ \lambda \f$:
 
        \f[
            \frac{D\lambda}{Dt} = a(1 - \lambda)^b - c \lambda \dot{\gamma}^d
        \f]
 
    The viscosity is then calculated using the expression
 
        \f[
            \nu = \frac{\nu_{\infty}}{{1 - K \lambda}^2}
        \f]
 
    Where the parameter K is given by:
 
        \f[
            K = 1 - \sqrt{\frac{\nu_{\infty}}{\nu_{0}}}
        \f]
 
    Here:
    \vartable
        \lambda         | structural parameter
        a               | model coefficient
        b               | model coefficient
        c               | model coefficient
        d               | model coefficient
        \dot{\gamma}    | stress rate [1/s]
        \nu_{0}         | limiting viscosity when \f$ \lambda = 1 \f$
        \nu_{\infty}    | limiting viscosity when \f$ \lambda = 0 \f$
    \endvartable
 
    Reference:
    \verbatim
        Barnes H A, 1997.  Thixotropy - a review.  J. Non-Newtonian Fluid
        Mech 70, pp 1-33
    \endverbatim
 
SourceFiles
    lambdaThixotropic.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef lambdaThixotropic_H
#define lambdaThixotropic_H
 
#include "laminarModel.H"
#include "linearViscousStress.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
namespace laminarModels
{
 
/*---------------------------------------------------------------------------*\
                    Class lambdaThixotropic Declaration
\*---------------------------------------------------------------------------*/
 
template<class BasicMomentumTransportModel>
class lambdaThixotropic
:
    public linearViscousStress<laminarModel<BasicMomentumTransportModel>>
{
    // Private data
 
        //- Model a coefficient
        dimensionedScalar a_;
 
        //- Model b coefficient
        dimensionedScalar b_;
 
        //- Model d coefficient
        dimensionedScalar d_;
 
        //- Model c coefficient (read after d since dims depend on d value)
        dimensionedScalar c_;
 
        //- Limiting viscosity when lambda = 1
        dimensionedScalar nu0_;
 
        //- Limiting viscosity when lambda = 0
        dimensionedScalar nuInf_;
 
        //- Model coefficient
        dimensionedScalar K_;
 
        //- Switch for optional Bingham plastic handling
        //  Set by the presence of the sigmay entry
        bool BinghamPlastic_;
 
        //- Optional Bingham plastic yield stress [m^2/s^2]
        dimensionedScalar sigmay_;
 
        //- Residual alpha
        //  Used to stabilise the solution of the lambda equation
        //  where the phase-fraction is below this value
        //  Defaults to 1e-6
        dimensionedScalar residualAlpha_;
 
        //- Structural parameter
        //  0 = freestream value (most liquid)
        //  1 = fully built (most solid)
        volScalarField lambda_;
 
        //- The non-Newtonian viscosity field
        volScalarField nu_;
 
 
    // Private Member Functions
 
        //- Calculates and returns the viscosity from the current lambda
        tmp<volScalarField> calcNu
        (
            const volScalarField& strainRate
        ) const;
 
        //- Returns the current strain rate from the velocity field
        tmp<volScalarField> strainRate() const;
 
 
public:
 
    typedef typename BasicMomentumTransportModel::alphaField alphaField;
    typedef typename BasicMomentumTransportModel::rhoField rhoField;
 
 
    //- Runtime type information
    TypeName("lambdaThixotropic");
 
 
    // Constructors
 
        //- Construct from components
        lambdaThixotropic
        (
            const alphaField& alpha,
            const rhoField& rho,
            const volVectorField& U,
            const surfaceScalarField& alphaRhoPhi,
            const surfaceScalarField& phi,
            const viscosity& viscosity
        );
 
 
    //- Destructor
    virtual ~lambdaThixotropic()
    {}
 
 
    // Member Functions
 
        //- Read momentumTransport dictionary
        virtual bool read();
 
        //- Return the effective viscosity
        //  i.e. the lambdaThixotropic viscosity
        virtual tmp<volScalarField> nuEff() const;
 
        //- Return the effective viscosity on patch
        virtual tmp<scalarField> nuEff(const label patchi) const;
 
        //- The lambdaThixotropic viscosity is not predicted
        virtual void predict()
        {}
 
        //- Correct the lambdaThixotropic viscosity
        virtual void correct();
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace laminarModels
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#ifdef NoRepository
    #include "lambdaThixotropic.C"
#endif
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //