[Tibo99]

Hi everyone,

I'm looking to implement a correction factor to the velocity for the k-e turbulence model.

I try to find the exact location in the code where I should apply the factor but I'm not quite sure.

The factor is apply on the Laplacian term.

I'm guessing it's in the 'UEqn.H' file but I don't find the Laplacian term in there.

[dlahaye]

Laplacian term is inside turbulence->divDevSigma(U). See e.g. line 9 of https://github.com/OpenFOAM/OpenFOAM...pleFoam/UEqn.H

[Tibo99]

Thank for replying!

I have openfoam v1906 and it's 'turbulence->divDevReff(U)' instead of 'turbulence->divDevSigma(U)'.

It's probably the same term?

[ecles]

Hello!

Could you please tell me where divDevSigma(U) is currently implemented? In OF 8, I tried to search in:
src/MomentumTransportModels/incompressible/IncompressibleMomentumTransportModel/IncompressibleMomentumTransportModel.C

(https://cpp.openfoam.org/v8/Incompre...ce.html#l00118)

But it seems to be currently not implemented.

[Tobermory]

https://cpp.openfoam.org/v8/Incompre...8C_source.html, line 106

[ecles]

Yes, but then when you follow the code:

template<class TransportModel>
Foam::tmp<Foam::fvVectorMatrix>
Foam::IncompressibleMomentumTransportModel<Transpo rtModel>::divDevSigma
(
volVectorField& U
) const
{
return divDevTau(U);
}


When you go to divDevTau:

template<class TransportModel>
Foam::tmp<Foam::fvVectorMatrix>
Foam::IncompressibleMomentumTransportModel<Transpo rtModel>::
divDevTau
(
volVectorField& U
) const
{
NotImplemented;

return divDevSigma(U);
}

What's going on?

Thanks!

[Tobermory]

Yes, it IS confusing, since there is a lot of use made of templating. The definition of divDevTau is done in the viscosity model, eg in:
line 81 of https://cpp.openfoam.org/v8/linearVi...8C_source.html
for the turbulence models that us a linear viscous stress, like kEpsilon.

[ecles]

Thank you!

I still do not see how divDevTau in the selected viscosity Model is accessed by IncompressibleMomentumTransportModel<TransportMode l>.

I tried to follow the classes:IncompressibleMomentumTransportModel->MomentumTransportModel->incompressibleMomentumTransportModel->momentumTransferModel, but I could not figure it out.

Could you help me?

[Tobermory]

The short answer (I think!) is that the turbulence model is instantiated as an object of type linearViscousStress<BasicMomentumTransportModel>, and has its own member function divDevTau() (as defined in linearViscousStress.C). The call in the solver to turbulence->divDevSigma(U) calls this function, as we saw from the earlier posts.

An incredible amount of detail is glossed over in the above "short answer".
My advice, if you truly want to understand this, is to clear a few days from your schedule and then take a BIG piece of paper and draw out the connections between the classes, start working through it and make notes as you go. It is really complex - especially the turbulence model, which involves multiple levels of RTS selection (you'll need to understand RTS, to thoroughly understand how the class structure all fits together; if you're not up to speed on RTS, then start by checking out https://openfoamwiki.net/index.php/O...tion_mechanism, but be aware that the full implementation in OpenFOAM is much more intricate/complex than the wiki page suggests, with many of the key features buried in macros).

If you do invest the time, you will learn a huge amount about the code ... so I do recommend it, but do write some notes since otherwise you may find that your moment of understanding evaporates quickly! Good luck.