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Old   January 20, 2005, 00:09
Default fundamental concepts of turbulence
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Dear all,

I am now confusing about the fundamental concepts of turbulence.

What's fully developed turbulence? Surely we could see the Re is high enough, but we don't know the exact value for the word "high" for a given complex flow. There should exist some criteria to determine the flow state. I have found some one use turbulent energy spectrum to judge whether it is fully developed turbulence or not based on -5/3. I don't know whether this is a general method.

Any comment is welcome, if possible please give the references. thanks a lot!

regards, sincerely, sarah
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Old   January 20, 2005, 06:08
Default Re: fundamental concepts of turbulence
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Actually the concept of "full fledged" turbulence has been questioned by Barenblatt (see his book on scaling and self-similarity) and Chorin. The main point of the argument is that is that the concept of full-fledged turbulence is one of mathematical simplification (complete similarity as Re-> infinity) which may or may not be correct; i.e. there may be incomplete similarity in which case the Re dependence does not go away as Re-> infinity.

Similar arguments have been used to suggest that the log-law should be replaced by an Re-dependent power law.

I'd recommend reading G.I.Barenblatt's book Scaling, Self-similarity, and Intermediate Asymptotics

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Old   January 20, 2005, 10:56
Default Re: fundamental concepts of turbulence
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Thank you very much for your reply.

You are right at disagreement about power law or log-law. Your comments is invaluable and I very appreicaite it.

thanks again

regards, sarah
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