Y+ range for different turbulence models and wall functions
 

Hello everyone
I read somewhere that the Y+ range for different turbulence models is as follows:

Spalart Almaras : Y+~1
k-ω : Y+<1
K-ε/standard wall function : 30<Y+<300
K-ε/scalable wall function : Y+>11
K-ε/Non equilibrium wall function : 30<Y+<300
K-ε/Enhance wall treatment : Y+<5


* Is the above correct?
* Can anyone suggest a valid reference for Y+ ranges?


Unfortunately, there is no exact reference for Y + and in different books and websites, there are different explanations that are confusing.


Thanks in advance

Fluent theory guide is useful for getting these numbers.

In Fluent, K-w,Spalart Almaras and Menter Lechner treatement are y+ insensitive. That dosen't mean using a good y+ won't give you a better solution. There's no strict definition for y+ range these days, depends on how accurate you wanna be. Also as far as I know, scalable wall function helps avoid getting bad results from standard wall funstion in case of grid refinement. Not sure if there's a recommended y+ for scalable. Feel free to correct me if I'm wrong.

Thanks for your reply.

Generally, when you are using models able to solve directly for the variables at the wall, y+ should be <= 1 or at least <5 (as far as I know, this is the y+ limit related to the viscous sublayer within the BL region). Instead, when you are adopting wall funtions, generally you need to maintain y+ within the logarithmic range, so 30 < y+ < 300 (I know it is true at least for standard and non-equilibrium).

I do not know if specific intervals exist for enhance or scalable wall functions; for more info, you can also try to have a look at the original scientific papers ;)