Automatic wall treatment in CFX
 

CFX uses automatic wall treatment for k-omega based models. According to CFX manual, when this option for wall treatment is selected, CFX automatically switches from between wall function approach and low Re approach depending upon the grid spacing near the wall.
Below what y+ (i.e. the non-dimensional distance of first mesh node from wall) does CFX switch from wall function approach to low Re approach for k-omega based models?

At y+=11.06, but I believe a smooth blend between the two approaches is used, so you won't get a sudden change at exactly that y+ value.

according to Menter above yplus 30 wall function and below yplus 2 low re formulation and between 2 and 30 blending of them

Thank you stumpy and Far for the info. Is any detail of this blending available aywhere? I could not find in the help guides.

yes it is available in paper by Knopp (send me email address) in very much detail from basic to implementation into cfd code but little bit different than menters. For menter blending forumulae please to his 1998 and 2003 paper for scalable wall function and automatic wall treatment respectively. Very basic details are also given in CFD theory guide

please read cfd theory guide as CFX theory guide

Thanks Far again for the info !. I have sent my email address to you by message. Please send me the paper by Knopp.
Thanks again !

Dear
Did you find the papers useful ?
Best Regards
Far

Hi Far,

Many thanks for sending the papers. Yes, the papers are indeed very useful, especially the second one by Knopp. Its been a great help

Dear
You can also contact knopp through email. He is great person and will surely help you in understating the paper and topic in depth.

Hi Stumpy,
can i ask where can i find a reference about the y+=11.06 value. is it for sure the limit value is 11.06, i need some references to write in my thesis.
thanks

have a look on this paper

http://num.math.uni-goettingen.de/ba...ings/knopp.pdf

http://www.os-cfd.ru/cfd_docs/wall_f..._functions.pdf

This is intersection point of linear law and log law. That is applicable for the older wall treatment. For hybrid wall function (automatic wall treatment for kw based models) the limits are:

Y < 6 : integration to wall approach
Y+ 6-30 : blending of both approaches
Y+ > 30 : standard wall function

hi every body.
I have some questions about wall functions that are available in CFX and FLUENT:
1-I want to know that is "y+ Intensive wall treatment omega-equation" in FLUENT exactly the same as "Automatic near-wall treatment for omega-based models" in CFX?
2-Is the near wall treatment in spalart-allmaras turbulent model in FLUENT exactlythe same as "Automatic near-wall treatment for omega-based models" in CFX and "y+ Intensive wall treatment omega-equation" in FLUENT?
3-what is the difference between "Automatic near-wall treatment for omega-based models" in CFX and "Menter-Lechner epsilon-equation" in FLUENT (it seems that both formulations are the same)?

Hello Sir,

I also intend to understand how this mechanism work. So would you please send this paper to me as well so that I can clearly understand this concept. I would be very grateful for that.

My email address is: vishu343@gmail.com

Thank you very much.