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Old   October 19, 2006, 08:20
Default Yplus in CFX
  #1
Eric
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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
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Old   October 19, 2006, 11:32
Default Re: Yplus in CFX
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Bian
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Refer to Guidelines for Mesh Generation in CFX Help. Basically, Yplus>20 (<200) for wall function. Yplus<2 for low-Re model.

BB
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Old   October 19, 2006, 16:55
Default Re: Yplus in CFX
  #3
Glenn Horrocks
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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
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Old   October 20, 2006, 00:13
Default Re: Yplus in CFX
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Eric
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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
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Old   October 20, 2006, 00:23
Default Re: Yplus in CFX
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TB
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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.
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Old   October 20, 2006, 06:01
Default Re: Yplus in CFX
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Johnny
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Also you should ideally have 10 nodes or so in the BL.
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Old   October 21, 2006, 00:51
Default Re: Yplus in CFX
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TB
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Hi, Johnny. This is a general guideline only. You may need a lot more if boundary layer flow is important in your analysis.
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Old   October 22, 2006, 07:32
Default Re: Yplus in CFX
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Eric
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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
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Old   October 23, 2006, 10:19
Default Re: Yplus in CFX
  #9
Chebeba
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Make the innermost mesh layer thinner. Y+ is directly proportional to the cell height.
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Old   October 23, 2006, 20:47
Default Re: Yplus in CFX
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TB
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You have to limit the growth rate between adjacent layers as well.... I usually set it around 1.1~1.3
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Old   November 10, 2006, 10:44
Default renolds number-flow type
  #11
naveen
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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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