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Eric October 19, 2006 08:20

Yplus in CFX
 
Dear Sir,

I was really confused in CFX Yplus. I can check the value of Yplus in CFX-post, but which is good? Yplus>11 or Yplus<11 Thank you in advance.

Best Regards Eric

Bian October 19, 2006 11:32

Re: Yplus in CFX
 
Refer to Guidelines for Mesh Generation in CFX Help. Basically, Yplus>20 (<200) for wall function. Yplus<2 for low-Re model.

BB

Glenn Horrocks October 19, 2006 16:55

Re: Yplus in CFX
 
Hi,

Or use the automatic wall functions approach and let the solver take care of it, then you only have to worry about mesh independance.

Glenn Horrocks

Eric October 20, 2006 00:13

Re: Yplus in CFX
 
Thank you very much for the kind reply

My simulation is compressible in a pipe. So, If 20 < Yplus <200, the resulte is acceptable. Is it right?

Thank you in advance.

Eric

TB October 20, 2006 00:23

Re: Yplus in CFX
 
It depends. You still need to validate & verify your solution. You should treat Y+ value as an indicator to minimise the numerical error, not to judge the accuracy of your solution.

Johnny October 20, 2006 06:01

Re: Yplus in CFX
 
Also you should ideally have 10 nodes or so in the BL.

TB October 21, 2006 00:51

Re: Yplus in CFX
 
Hi, Johnny. This is a general guideline only. You may need a lot more if boundary layer flow is important in your analysis.

Eric October 22, 2006 07:32

Re: Yplus in CFX
 
Dear Friends,

Thank you for the reply and the discussion. If y+ plus is not good in my simulation, what can I do?

Many thanks

Eric

Chebeba October 23, 2006 10:19

Re: Yplus in CFX
 
Make the innermost mesh layer thinner. Y+ is directly proportional to the cell height.

TB October 23, 2006 20:47

Re: Yplus in CFX
 
You have to limit the growth rate between adjacent layers as well.... I usually set it around 1.1~1.3

naveen November 10, 2006 10:44

renolds number-flow type
 
hi all,

This is naveen.i am working with the cfx 10,where i am analysing air flow past a circular cylinder.and my reynolds number is 7e+4.i would like to know for such kind of reynolds number ,which fluid flow ( transition flow or turbulence flow ) will influence more on my problem and why? how can i know exact critical reynolds number(transition point) for my case.

i want to hear from you,

thanks all

regards,

Naveen


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