[kakkapriyesh]

Hi,

I was going through the formulation for K-Eqn and noticed that there is an term DkEff which is an addition of Nut and nu but nu multiplied by gradient of Ksgs (k_) term is not present in the paper of Kim and Menon,

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(Ce(D, KK)*alpha*rho*sqrt(k_)/this->delta(), k_)
       + kSource()
       + fvOptions(alpha, rho, k_)
     );

From Dynamick.H

        //- Return the effective diffusivity for k
         tmp<volScalarField> DkEff() const
         {
             return tmp<volScalarField>
             (
                 new volScalarField("DkEff", this->nut_ + this->nu())
             );
         }

similarly for calculating Ce (coefficient of dissipation) NuEff has been used instead of nu

Am I missing something obvious?

I have attached the snip of the formula present in Kim and Menon

[syavash]

Originally Posted by kakkapriyesh

Hi,

I was going through the formulation for K-Eqn and noticed that there is an term DkEff which is an addition of Nut and nu but nu multiplied by gradient of Ksgs (k_) term is not present in the paper of Kim and Menon,

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(Ce(D, KK)*alpha*rho*sqrt(k_)/this->delta(), k_)
       + kSource()
       + fvOptions(alpha, rho, k_)
     );

From Dynamick.H

        //- Return the effective diffusivity for k
         tmp<volScalarField> DkEff() const
         {
             return tmp<volScalarField>
             (
                 new volScalarField("DkEff", this->nut_ + this->nu())
             );
         }

similarly for calculating Ce (coefficient of dissipation) NuEff has been used instead of nu

Am I missing something obvious?

I have attached the snip of the formula present in Kim and Menon

Hi,

I came across this issue as well. Did you find an explanation for that?

Thanks,
Syavash

[LuckyTran]

It's not a missing/extra term, but the terms have been re-arranged. Notice the term on the left hand side in foam is:

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

which needs to be balanced by the source/sink in order to make it equivalent

- fvm::Sp(Ce(D, KK)*alpha*rho*sqrt(k_)/this->delta(), k_)

Otherwise, there should be a divergence of a gradient in FOAM (which you don't see anywhere).


The reason for splitting the term into two is numerical.