[gu1]

Hello,

If I want to obtain the production values and in particular, destruction term of the equation below, how do I do it? Could anyone guide me?

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()
      + fvModels.source(alpha, rho, k_)
    );

Thanks

[Tobermory]

I used to think that this was impossible, without creating your own clone of the turbulence model and explicitly adding in coding to make the field write to disk. However - I found this recently: at the bottom of the controlDict in the simpleFoam/pitzDaily tutorial (foundation v8) is the following:

cacheTemporaryObjects
(
    kEpsilon:G
);

functions
{
    #includeFunc writeObjects(kEpsilon:G)
}

and you can probably guess what it is doing - cacheing the production term in the Registry, thereby making it available for the writeObject FO. Sure enough, when you run the tutorial case, there is the data.

So, you can force the code to write tmp<> variables ... which is not quite what you are after since the destruction term is expressed as a composite term, and not as a tmp<> volField, but it may be a step in the right direction? Good luck.

[NotOverUnderated]

Originally Posted by Tobermory

I used to think that this was impossible, without creating your own clone of the turbulence model and explicitly adding in coding to make the field write to disk. However - I found this recently: at the bottom of the controlDict in the simpleFoam/pitzDaily tutorial (foundation v8) is the following:

cacheTemporaryObjects
(
    kEpsilon:G
);

functions
{
    #includeFunc writeObjects(kEpsilon:G)
}

and you can probably guess what it is doing - cacheing the production term in the Registry, thereby making it available for the writeObject FO. Sure enough, when you run the tutorial case, there is the data.

So, you can force the code to write tmp<> variables ... which is not quite what you are after since the destruction term is expressed as a composite term, and not as a tmp<> volField, but it may be a step in the right direction? Good luck.

That's interesting, thank you for sharing that tip

I use OpenFOAM v2312 so that trick doesn't work unfortunately.

But I am not sure why do you need to clone the turbulence model to compute the production term when it could be simply computed using:



The production term of TKE is the double inner product of the Reynolds stress tensor and the velocity gradient tensor.

This can be computed using a coded function object (or expressions?).

Regards

[Tobermory]

The benefit of cloning the model rather than trying to calculate it yourself is that you see exactly the values that are being used in the turbulence model ... the value you calculate may be slightly different.