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Old   April 26, 2005, 09:40
Default RANS vs LES
Pei Hsieh
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Can anyone here explain the differences between RANS and LES? When to choose one and not the other? Or please advise me websites that discusses these. Thanks!

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Old   April 26, 2005, 17:48
Default Re: RANS vs LES
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RANS corresponds to an average of several repetitions of the same turbulent process so that mean values are obtained.

LES simulates the turbulent structures (not all but the ones with a scale larger than the resolution asked by the user).

As mean values are smoother to solve than the eddies roll-over, RANS demands less computational efforts than LES.

For the turbulent scales which are to small to be solved in LES, turbulent models are localy applied to evaluate the overall level of turbulence with structure scales smaller than the resolved scale. These SubGgrid Scale models (because the resolved scale is given more or less by the grid size) may have some common points with RANS models even if the underlying theories are conceptually different.
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Old   April 27, 2005, 08:40
Default Re: RANS vs LES
Pei Hsieh
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Thanks Guillaume!

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