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-   -   Is Y plus =3 ok for standard wall function??? (http://www.cfd-online.com/Forums/fluent/36582-y-plus-3-ok-standard-wall-function.html)

Thomas May 6, 2005 15:26

Is Y plus =3 ok for standard wall function???
 
Hello fluent users

is y+=3 ok for the standard wall function approach? In the users guide they say the y+ value should be at about 30.

Or can i also use the enhanced wall treatment when the y+ is also at about 3 to 4?

thanks for your help

thomas

pUl| May 7, 2005 00:08

Re: Is Y plus =3 ok for standard wall function???
 
Manual wise NO. However, I would love if someone could clearly (and i mean CLEARLY) explain the difference in results (if any) if y+ = 30 is not adhered to, when using Std. Wall functions.

kamesh May 9, 2005 14:11

Re: Is Y plus =3 ok for standard wall function???
 
hi guys The value of Y plus depends on the type of turbulence model.for example K-epsilon (infact every) Turbulence model without wall treatment assumes full turbulence in domain of integration.If the value of y+ is greater than 30 i.e some where in the middle(i mean not near wall region), the results of turbulence model is fairly good with experimental values. So if we dont take wall treatment into consideration one should take y+ more than 30 to get reasonably good results...... kamesh

Riaan May 10, 2005 15:13

Re: Is Y plus =3 ok for standard wall function???
 
Well, in my cases, I have y+=1 even when using wall functions. The model I am using is the Realizable K-eps with Non-equilibrium wall functions.

For the SA model, y+ = 1 and y+>30 give similar results and compare well with experimental data (at least for delta wings at alpha <10deg)

kamesh May 12, 2005 13:08

Re: Is Y plus =3 ok for standard wall function???
 
hi if u use standatd wall functions ther will be no much pblm if u have less y+ value.U should be careful about wall your results when you are not using wall functions.


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