About the nut wall function in RAS

spwater · November 15, 2009, 07:11

Hello everyone,
This is Pei, I have a question about the wall function of nu in RAS model, I found in the code,

nutw[faceI] = nuw[faceI]*(yPlus*kappa_/log(E_*yPlus) - 1.0)

However, the book I am reading says it should be

nutw[faceI] = nuw[faceI]*(yPlus*kappa_/log(E_*yPlus) )

Can angone explain the difference? Thank you very much!

Anne Lincke · October 28, 2011, 11:37

Hey Pei,

In the log-Layer we can assume that nu_t >>nu
Therefore we can approximate

nuw[faceI]*(yPlus*kappa_/log(E_*yPlus) - 1.0) = nuw[faceI]*yPlus*kappa_/log(E_*yPlus)-nuw[faceI]
~~nuw[faceI]*yPlus*kappa_/log(E_*yPlus)

November 15, 2009, 07:11	About the nut wall function in RAS	#1
spwater New Member Shui Pei Join Date: Mar 2009 Posts: 27 Rep Power: 17	Hello everyone, This is Pei, I have a question about the wall function of nu in RAS model, I found in the code, nutw[faceI] = nuw[faceI](yPluskappa_/log(E_yPlus) - 1.0) However, the book I am reading says it should be nutw[faceI] = nuw[faceI](yPluskappa_/log(E_yPlus) ) Can angone explain the difference? Thank you very much!

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October 28, 2011, 11:37		#2
Anne Lincke Senior Member Anne Gerdes Join Date: Aug 2010 Location: Hamburg Posts: 168 Rep Power: 16	Hey Pei, In the log-Layer we can assume that nu_t >>nu Therefore we can approximate nuw[faceI](yPluskappa_/log(E_yPlus) - 1.0) = nuw[faceI]yPluskappa_/log(E_yPlus)-nuw[faceI] ~~nuw[faceI]yPluskappa_/log(E_*yPlus)