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Old   August 8, 2013, 15:28
Post "Y plus" very important!!!
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Hi!

I need some information about the expected Y plus value for each turbulence model.

Please help me!!!
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Old   August 8, 2013, 15:38
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hello,
Y+ is very effective in the calculation, and the value may be 5-24 or 24-500 for RANS turbulence model. But it can be changeable for your simulation and results
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Old   August 8, 2013, 15:57
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thank u for your response but i need a detailed information, such as how much acceptable y plus for realizable KE?
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Old   August 8, 2013, 18:31
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Actually, every boundary layer is divided into three parts: 1-sublayer 2-buffer layer 3-log law layer. All RANS turbulent models estimate viscosity and this viscosity is also included of molecular and/or turbulent ones. The importance of y+ lies in the fact that which part the center point of a mesh situates. Therefore, turbulent model estimates viscosity due to that part. In the buffer layer, we cannot have a good anticipation, as a consequence, it makes a recommend to avoid a y+ value in buffer layer. I enclose a picture to give the points





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thank u for your response but i need a detailed information, such as how much acceptable y plus for realizable KE?
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Old   August 10, 2013, 01:53
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Quote:
Originally Posted by behest View Post
Actually, every boundary layer is divided into three parts: 1-sublayer 2-buffer layer 3-log law layer. All RANS turbulent models estimate viscosity and this viscosity is also included of molecular and/or turbulent ones. The importance of y+ lies in the fact that which part the center point of a mesh situates. Therefore, turbulent model estimates viscosity due to that part. In the buffer layer, we cannot have a good anticipation, as a consequence, it makes a recommend to avoid a y+ value in buffer layer. I enclose a picture to give the points
Please explain more. Thanks
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Old   August 10, 2013, 06:48
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my case study is a simplified car body and i want to use RKE or SST KW turbulence models. for more accurate results, how much should be y plus values?!
which one is correct? 30< y+ <300 or y+ <5 ?

Last edited by Qube; August 10, 2013 at 10:35.
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Old   August 10, 2013, 08:15
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Dear friend
The drag coefficient is depend to y+ value. I suggest to you to consider 30< y+ <300 initially; but if the results was not sufficient precision, then use another y+.
It has had an experience that the y+ <5 is achieved more accuracy

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Dear saeed!
my case study is a simplified car body and i want to use RKE or SST KW turbulence models. for more accurate results, how much should be y plus values?!
which one is correct? 30< y+ <300 or y+ <5 ?
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Old   August 10, 2013, 10:33
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thank you so much!
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