EnigmaFluids 
July 10, 2020 16:11 
Openfoam nut and k_sgs equation
Greetings, I have noticed while completing LES that openfoam uses the equation
or if you check WALE.C
this>nut_ = Ck_*this>delta()*sqrt(this>k(fvc::grad(this>U_)));
but where does this equation come from? I have been reading the original smagorinsky model and also WALE model papers, but I don't see it contained there. I am looking for a literature source because I want to know if this k_sgs is actually a physical quantity or just an intermediate calculation on the way to get nut.
For example, in the original WALE paper by Nicoud and Ducros (1999), we notice that the model gives nut alone and not k_sgs. However, I assume that openfoam calculates k_sgs first and then nut after, for coding convenience. I would like to know whether the openfoam k_sgs is a real quantity so I can estimate whether 80% of the turbulence kinetic energy is being resolved in my field via
So once again, where does this equation come from? Thanks!
