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Old   December 9, 2008, 15:41
Default Turbulent Reynolds
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Michael Groll
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I have seen several values for Reynolds number while doing some research on this topic for what is considered to be turbulent flow. I have seen, at minimum, >2,000 Re. Then I have seen >3,000, >4,000, and I have seen a couple sources state that >10,000 Re is considered turbulent. How is one to determine an accurate measurement for what is considerd turbulent flow?
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Old   December 9, 2008, 18:28
Default Re: Turbulent Reynolds
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Glenn Horrocks
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Hi,

It depends on many factors, that is why there is not a single "accurate" number. I assume you are talking about pipe flow. The Re for transition to turbulence depends on many factors, such as upstream disruptions, surface roughness, vibrations and many others. In a lab where you can make an almost ideal laminar flow you can extend the transition point to quite high Re numbers. In the real world with rough pipes, vibrations and upstream effects it pushes it back to around Re=2000.

On top of that there is also hysteresis effects - the Re number is going from turbulent to laminar flow tends to be lower than going from laminar to turbulent.

Glenn Horrocks
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