一个关于K方程SGS模型的问题:



  • 在OF3.0中,K方程的代码如下:

        tmp<fvScalarMatrix> kEqn
        (
            fvm::ddt(alpha, rho, k_)
          + fvm::div(alphaRhoPhi, k_)
          - fvm::laplacian(alpha*rho*DkEff(), k_)
         ==
            alpha*rho*G
          - fvm::SuSp((2.0/3.0)*alpha*rho*divU, k_)
          - fvm::Sp(this->Ce_*alpha*rho*sqrt(k_)/this->delta(), k_)
          + kSource()
        );
    

    其中扩散项

    fvm::laplacian(alpha*rho*DkEff(), k_)
    

            tmp<volScalarField> DkEff() const
            {
                return tmp<volScalarField>
                (
                    new volScalarField("DkEff", this->nut_ + this->nu())
                );
            }
    

    简单地说,就是K方程的扩散项粘度用的是 nut+nu。
    这里的nut:

    this->nut_ = Ck_*sqrt(k_)*this->delta();
    

    但是,在文献Menon S, Yeung P K, Kim W W. Effect of subgrid models on the computed interscale energy transfer in isotropic turbulence[J]. Computers & Fluids, 1996, 25(2):165–180.中,公式却是这样的:

    0_1465025568118_upload-70c21c14-c5db-4943-8990-14bf3e631d82
    扩散项粘度用的是 nut。
    有人知道怎么回事吗?



  •     tmp<fvScalarMatrix> kEqn
        (
            fvm::ddt(alpha, rho, k_)
          + fvm::div(alphaRhoPhi, k_)
          - fvm::laplacian(alpha*rho*DkEff(), k_)
         ==
            alpha*rho*G
          - fvm::SuSp((2.0/3.0)*alpha*rho*divU, k_)
          - fvm::Sp(this->Ce_*alpha*rho*sqrt(k_)/this->delta(), k_)
          + kSource()
        );
    

    除了粘度项,其他项均和文献一样?



  • 是的,除了一些关于可压和不可压的区别之外。还有就是O F中假设K的普朗特数为1。



  • Description
        One equation eddy-viscosity model
    
        Eddy viscosity SGS model using a modeled balance equation to simulate the
        behaviour of k.
    
        Reference:
        \verbatim
            Yoshizawa, A. (1986).
            Statistical theory for compressible turbulent shear flows,
            with the application to subgrid modeling.
            Physics of Fluids (1958-1988), 29(7), 2152-2164.
        \endverbatim
    
        The default model coefficients are
        \verbatim
            kEqnCoeffs
            {
                Ck                  0.094;
                Ce                  1.048;
            }
        \endverbatim
    
    SourceFiles
        kEqn.C
    

    我建议参考Yoshizawa, A. (1986).年的文章来验证。有可能Menon S. 1996年的文章和这个文献不同。



  • 谢谢,那个我也看了(但没仔细看,只是特意找了扩散项)。应该也是和Menon一样的结论。因为Menon的文章截图比较方便,才引用他的


Log in to reply