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July 30, 2009, 02:53 |
need help (SGS viscosity)
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#1 |
New Member
LiuYuxuan
Join Date: Jun 2009
Posts: 7
Rep Power: 16 |
is there are anyone know the different between SGS viscosity (LES model) and turbulent viscosity (K-omega model)?
Thank you very much! |
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July 31, 2009, 10:48 |
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#2 |
Senior Member
Aroon
Join Date: Apr 2009
Location: Racine WI
Posts: 148
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The difference is the way in which the turbulent stresses are filtered or averaged.
In any RANS model the turbulent viscosity is derived from the difference between the actual value and the time averaged value. In SGS, the turbulent viscosity is derived from the difference between teh actual values of velocities and the resolved velocities (obtained from sub-grid filters). |
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August 2, 2009, 23:32 |
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#3 |
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LiuYuxuan
Join Date: Jun 2009
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Thank you very very much!
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August 21, 2009, 12:07 |
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#4 |
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federico
Join Date: Aug 2009
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SGS is the Sub Grid Scale stress, the part of the stress which is not resolved by your grid because for example it is too coarse. This contribution provide the effect of just a small fraction of the Reynolds stress because most of it is already resolved. Instead in RANS model the turbulent viscosity must provide all the Reynolds stress
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August 23, 2009, 04:59 |
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#5 | |
New Member
LiuYuxuan
Join Date: Jun 2009
Posts: 7
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Quote:
you said that sub grid scale stress provide the effect of just a small fraction of reynolds stress, so is this mean, change another word, the sub grid scale stress just divide my grid into more smaller and then caculate this smaller grid? By the way, I am a beginner in CFD, I am not so sure that is a silly question! Thank you in advance! |
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August 24, 2009, 12:01 |
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#6 | |
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federico
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Quote:
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