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-   -   Is Y+ depends on the tubulence model? (https://www.cfd-online.com/Forums/main/92266-y-depends-tubulence-model.html)

 krishnag2002 September 8, 2011 07:23

Is Y+ depends on the tubulence model?

If we use different turbulence models, the target Y+ will change accordingly?

 cfd_newbie September 8, 2011 07:52

Quote:
 Originally Posted by krishnag2002 (Post 323395) If we use different turbulence models, the target Y+ will change accordingly?
Does you question mean -
"If you use different turbulence models we should target different Y+ while making grids ?"

 krishnag2002 September 8, 2011 09:18

 cfd_newbie September 8, 2011 23:36

 mettler September 9, 2011 08:26

yes, it does

for the turbulence model chosen, a preferable range of Y+ must be obtained to be considered valid the analysis. What drives this range will be the size of the first cell adiacent to the wall.

 Far September 12, 2011 15:44

for example yplus 30 or greater for K epsilon based models and y+1 ~ for the SST, BSL and SA type models. It is the preferable approach.

although we can extend the K epsilon model to yplus = 1 range by using the special damping functions as implemented in the Fluent

similarly SST model can be used with the yplus = 30 mesh

P.S: Yplus = 30 or greater implies we are not solving the viscous sub-layer (yplus 2 or less) and buffer layer (in between 2 and 30). It is also called wall function approach

Yplus = 1 implies we are resolving the viscous sub layer. It is necessary to use the yplus = 1 type mesh if flow is dominated by the separation and reattachment where wall function ceases to be valid

In commercial CFD codes after Yplus = 11.06 wall function approach is activated and below this viscous sub layer approach is used