[er_trebbia]

Hi all

In fluent theory guide, one can find that:

"In the DDES and IDDES implementations [of DES k-w], fd is used as defined for the Spalart-Allmaras model with the exception that the value of the constant is changed from 8 to 20."

But it is not clear how the model switch between RANS and LES approach.

My opinion is that in the equation

Fdes = max{ [Lt/(Cdes*Delta)]*(1-Fsst) ; 1}

this fd is just Fsst, but I am not sure, neither I can find any papers that explain that.
Am I wrong?

[er_trebbia]

Ok, I will answer to my own question.

To whom that could be interested, you can find how actually fluent uses the Spalart fd limiter giving a look to this paper:

M. S. Gritskevich et al., “Development of DDES and IDDES formulations for the k - ω shear stress transport model,” Flow, Turbul. Combust. 88, 431 (2012)