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why RNG k-e is better & what does RNG really mean?

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Old   August 7, 2006, 22:01
Default why RNG k-e is better & what does RNG really mean?
  #1
Bonnie White
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Hi,

I don't fully understand why RNG k-e model is better than k-e modle? Does it solve more internediate variables, thus more computationally expensive?

Since no classic textbook introduces RNG k-e model, I asked some CFD professors, but they cannot explain clearly to me why we need "RNG" tech? One of them just said that RNG is an "old" method after LES has been developed.

Any advice? Thank you.

Bo
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Old   August 8, 2006, 09:14
Default Re: why RNG k-e is better & what does RNG really m
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cadaei
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The RNG model uses a mathematical analysis called renormalization group theory to derive the constants in the k and e equations. In the standard k-e model the contants are entirely based on experimental data and are only applicable to the type of flow the constants are based on.

Since the RNG constants are derived from theory the model is applicable to a wider range of flows. As far as I can remember the RNG model only has one extra pressure strain term than the standard k-e. The RNG is therfore only slightly more computationally expensive and yields more accurate results.

The LES model gives far better results than RNG but the grid requirements for LES make it very time consuming. The model to use depends on what you are trying to analyze and the resources that you have.
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