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Is Y+ depends on the tubulence model?

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Old   September 8, 2011, 07:23
Default Is Y+ depends on the tubulence model?
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If we use different turbulence models, the target Y+ will change accordingly?
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Old   September 8, 2011, 07:52
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Quote:
Originally Posted by krishnag2002 View Post
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 ?"
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Old   September 8, 2011, 09:18
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Yes Thanks in Advance
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Old   September 8, 2011, 23:36
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These 3 links might be useful -
Use of k-epsilon and k-omega Models
http://www.cfd-online.com/Wiki/RANS-...bulence_models
http://www.kxcad.net/STAR-CCM/online...ulence-15.html
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Old   September 9, 2011, 08:26
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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.
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Old   September 12, 2011, 15:44
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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

also check this link Comparison of fluent and CFX for turbomachinery
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Old   September 13, 2011, 02:06
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thanks for your information. now I have some idea about Y+
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