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Difference between LES and k-epsilon models??

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Old   March 28, 2011, 04:36
Default Difference between LES and k-epsilon models??
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Luc
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Hey,
does somebody could help me on that question, I don't really see what is the main difference between these two models and what are the main advantages or drawbacks of them. I've try to find the differences in many docs but this is not really explicit, and I don't really see the point.
If somebody can give me an anwser, I'll appreciate
bye
Lucos
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Old   March 28, 2011, 05:22
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Dynampally Pavitran
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  1. k-epsilon is a RANS model, where the governing equations are time averaged. This is called Reynolds time averaging.
  2. In LES, we filter(volume average) the equations. Therefore the filtered variables are functions of space and time.
  3. In RANS, all turbulent scales are modeled, whereas in LES the Large scales are resolved and the small isotropic subgrid scales are modeled.
  4. The Reynolds stress term in RANS and subgrid stress term in LES are defined differently.
  5. Although LES is relatively more accurate than RANS, it is computationally very expensive. As there are stringent conditions for generating the mesh.
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Old   March 28, 2011, 05:30
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Luc
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thank you very much Pavitran!
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