# Recomended value for y+?

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 September 20, 2004, 09:07 Recomended value for y+? #1 Joe Guest   Posts: n/a Looking for the y+ distance from the wall to the wall-adjacent cell when using the Non-Equilibrium Wall functions? Thank you /Joe

 September 20, 2004, 20:34 Re: Recomended value for y+? #2 carlos ortiz Guest   Posts: n/a I would recommend between 1 and 5 for mesh adaption.

 September 21, 2004, 01:01 Re: Recomended value for y+? #3 anindya Guest   Posts: n/a I believe you have the same rules as for standard wall functions, i.e. y+ > 30. Please check Fluent manual (chapter 10 on turbulence modeling)

 October 3, 2004, 09:07 Re: Recomended value for y+? #4 ap Guest   Posts: n/a If you use standard or non-equilibrium wall-function, you need to have 30 < y+ < 60. Values of y+ close to 1 are required by the enhanced wall treatment, but are not acceptable for wall-functions. Hi ap

 October 3, 2004, 09:08 Re: Recomended value for y+? #5 ap Guest   Posts: n/a This is not valid for wall functions, but for the enhanced wall treatment. Hi ap

 October 12, 2004, 15:28 Re: Recomended value for y+? #6 chenjiansheng Guest   Posts: n/a Hello, ap Why you always say Y+ is between(30,60)? As I know near 30 is ok! someone always use >11. Can you give some references? thanks

 October 12, 2004, 16:21 Re: Recomended value for y+? #7 ap Guest   Posts: n/a A good reference is Wilcox's book: D. C. Wilcox. Turbulence Modeling for CFD. DCW Industries, Inc., La Canada, California, 1998. For y+ < 11.225 FLUENT uses the linear law, while it switches to the log law for greater values of y+, which, however, is proven to be valid only for y+ about in the range 30 < y+ < 60. The more you go out of this range, the worst results you should expect, but keep in mind these are empirical results (all wall functions are based on empirical results). You're right, a value around 30 is ok, it's close to the range of validity. Hi ap

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