effect of turbulent intensity in RANS in Fluent
 

Dear Fellas,

I was curious that since T.I is u'/U where u' is fluctuating and U is the mean velocity, how come it comes into play in RANS where u' is zero. I mean in a mean flow how turbulent intensity is computed and what is its role/effect?

Anyone please?

To my understanding, RANS models are plain wrong when turbulence is low --> U' is very low. RANS model always presume the existence of a reasonable amount of turbulence.

Also, keep in mind, RANS models model (forgive th poor choice of words) the fluctuations, they do not solve them. You can have a quick look, say, for example, at k-espilon model. U' is appears in none of the turbulence equations used by the solver.

https://www.cfd-online.com/Wiki/Stan...-epsilon_model

That's my question that when we do not have u' how come TI is computed? RANS do compute fluctuations but rather product of fluctuations u'v' called as Reynolds Stress. Individual fluctuations are not computed and neither modeled.