Possibly Incorrect Cs used in the Tutorial: channel395DFSEM

Hi,

Please consider tutorials/incompressible/pimpleFoam/LES/channel395DFSEM

In the tutorial's README file, it is stated that:

Channel test case for ReTau=395,based on the reference:

Poletto, R., Craft, T., and Revell, A., 
"A New Divergence Free Synthetic Eddy Method for the 
Reproduction of Inlet Flow Conditions for LES",
Flow Turbulence Combust (2013) 91:519-539

In the page 531 of the above reference, it was reported that the Cs=0.065 was used for the case.

In constant/turbulenceProperties, the model coefficients that determine Cs are given as:

    kEqnCoeffs
    {
        Ce              1.048;
        Ck              0.07; // 0.094;
    }

Considering the Cs = f(Ce, Ck) relation (also assumed by the community) is as follows:

Cs^2 = Ck * sqrt(Ck/Ce)

Computing Cs according to this relation yields Cs~0.1345 rather than Cs=0.065. Assuming Ce=1.048 constant, Ck~0.02654 produces Cs=0.065 according to this definition. In practice, this means, the tutorial is more diffusive than the benchmark. (Admittedly, Cs~0.1345 is approximately twice the Cs=0.065. May explain this.)

If all aforementioned premises are correct, the tutorial in OpenFOAM currently does not exactly replicate the channel test case, as was mentioned, that the tutorial was based on.

Kind regards