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June 20, 2013, 15:37 |
Yplus
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#1 |
Member
rayan
Join Date: Jun 2013
Posts: 65
Rep Power: 12 |
Hi,
I want to know what's the "Y+" and what's the effect of YPLUS, WHY i MUST CHOISE az define value for Yplus, in LES model why i must choise Yplus =1? Thanks for your explications |
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June 21, 2013, 04:22 |
reply of Y+
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#2 |
New Member
CHAO
Join Date: Feb 2013
Posts: 6
Rep Power: 13 |
Hi.
Y+ represents the suitability evaluation of boundary layer thickness. |
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June 21, 2013, 06:50 |
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#3 |
Senior Member
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Y+ is importsant in relation to the known features of turbulent velocity profiles near the wall. For Equilibrium boundary layers, at low y+ (<5) it is linear, for high values (>30-50) and up to 0.1 delta (thickness of the boundary layer) it is logarithmic. For the first point near the wall in your grid you can define a value for y+, then you know if it is too high to resolve the full velocity profile or not. If not, you need a low Re turbulence model (which can go down to the wall), otherwise you will need a standard model with wall functions.
This is the basic matter in RANS. For LES it is quite different and y+ alone is useless. Wall parallel grid spacings matters as well. But this is a much longer story... |
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June 21, 2013, 07:05 |
another question
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#4 |
New Member
CHAO
Join Date: Feb 2013
Posts: 6
Rep Power: 13 |
That is a wonderful explanation.
Well,may I know if you know about the Detailed chemical reaction mechanism of gasoline and suitable references on this matter? Any help would be greatly appreciated. |
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June 21, 2013, 08:48 |
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#6 | |
Member
rayan
Join Date: Jun 2013
Posts: 65
Rep Power: 12 |
Verry good explanation
Thanks a lot I begin to undestund the importance of Y+ Thanks Quote:
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