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September 16, 2012, 13:58 
Y plus for various turbulence models

#1 
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TA Ramanathan
Join Date: Jul 2012
Location: India
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Dear all,
I am working on the study of wall treatment for different turbulence models (fluid domain as cyclone separator). This simulation is carrying out flow simulation alone for better understanding. In the above mentioned work, I need to know the effective range of y plus for various turbulence models such as kepsilon, komega, SST and RSM etc. I have searched but I could not get material which gives elaborated details. So, I wish to know the range of y plus has to be used or better if you give me link to come across the same. Thanks in advance. 

September 16, 2012, 18:44 

#2 
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Glenn Horrocks
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SST can handle any y+.
ke should be >11 komega should be <1 RSM should be >11 if using wall functions or anything if automatic. But the final decision on wall mesh resolution should always be determined by a sensitivity study in your case. 

September 17, 2012, 06:28 

#3 
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TA Ramanathan
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Hi Glenn,
Thank you for valuable details. I will check on each turbulence models and do for sensitivity study. 

September 18, 2012, 02:48 

#4 
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Hamed Abdul Majeed
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Hi,
Does these limits change: 1. If flow is internal or external. 2. Using wall functions Thank you Regards Hamed 

September 18, 2012, 19:41 

#5 
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Glenn Horrocks
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1. No.
2. If you use wall functions then you need y+>11. This is all basic application of the wall boundary condition theory. If you read up about the wall boundary condition and understand it then the reason for these answers become obvious. 

December 10, 2013, 02:37 

#6  
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MMS
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Quote:
Thanks. 

December 10, 2013, 04:13 

#7 
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Meimei Wang
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Are you sure that ke should be >11? Does CFX have low reynolds number Ke model like Fluent which likes to have Y+ < 0.2? I thought these two software are almost same at wall treatment for different turbulence modeling.
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Best regards, Meimei 

December 16, 2013, 01:11 

#8 
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As far as I understand CFX uses scalable wall functions with ke model. If mesh is too fine near the wall then CFX ignores this region by "mathematically" placing first mesh node at Y+ ~ 11.


December 16, 2013, 12:44 

#9  
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OJ
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Quote:
But the low Re keps models in FLUENT (LaunderSharma, YangShih etc) all use damping functions and redefined values of eps to regularise the extremities in k and eps near wall and hence integration to the wall is possible with Y+ values less than 1 etc. There are w based models both in CFX and FLUENT which are which are generally favoured. 

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