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Old   October 20, 2004, 05:16
Default Reynolds and Turbulent Flow
Frederic Dubinski
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I've got two questions here. I would be very pleased if someone could answer them!! Thanks

Q1--If during your analysis, you find that that Reynolds number changes the flow from laminar to turbulent as the water flows around the cooling jacket circumference, say half way round; Then would you change the calculation so that the rest was performed with a turbulent flow model.? Or would you leave it to calculate the rest still using a laminar flow model.

Q2--Can CFX cope well with flow regimes that vary in nature. "What does it do" so to speak.?

i.e. A flow that changes from laminar to transition and then turbulent flow during the flow path.?
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Old   October 20, 2004, 12:08
Default Re: Reynolds and Turbulent Flow
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I think u need use the turbulence model for the whole flow process.

in fact the laminar and turbulent flow share the same equations group except for the laminar flow all the turbulence parameters are negligible.
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Old   October 20, 2004, 13:57
Default Re: Reynolds and Turbulent Flow
Jarmo Monttinen
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For Q1:

I would use laminar approach up to the point of predicted transition unless you can match experimental results using the fully turbulent approach.

Chances are that the model is developed for a different problem, thus the transition criteria is different from the physical transition. Other possibility: tweak the parameters of the turbulence model so that when you run it fully turbulent, it matches the experiment.

-- Jarmo
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