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Old   March 14, 2005, 11:00
Default Is the flow turbulent?
  #1
Katarina Tenti
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Hi,

how does one in a general geometry (not tube) decide before CFD calculations that the flow therein will be turbulent? I have a geometry that is far from being a pipe and I would not know how to calculate a representative Reynolds number therein.

Thank you for your help.

- Katarina
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Old   March 15, 2005, 03:51
Default Re: Is the flow turbulent?
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Melaku Habte
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Hi,

If I am not mistaken, wasn't hydraulic diameter for this purpose? If you have a non-circular geometry, you can obtain an equivalent diameter based on its geometry and then based on that diameter you'll calculate Re_no. There are also some other correlations if you have a particular geometry.

rgds

Melaku H
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Old   March 15, 2005, 09:46
Default Re: Is the flow turbulent?
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khalid sultan
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Hi;

I would recommend "Michel method". For details see

(Viscous Fluid Flow) by: Frank M. White, 2nd edition, page 377 .

One more thing, eq.(5.38) in the above mentioned Ref., was later modified by another one which require some kind of iteration to be solved; to see this new form goto AIAA 2000-0048.

The above method could be easely implemented in any code -I assume !-

Hoping it would help

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Old   March 16, 2005, 06:49
Default Re: Is the flow turbulent?
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Katarina Tenti
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Hello Melaku,

thanks for the response! I have a situation where I think that recirculation areas act as "walls" of a narrowing, through which fluid is squeezed. If I calculate the hydraulic diameter of the actual geometry, I will get Re that are below those that occur locally.

Thanks, Katarina
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Old   March 16, 2005, 06:59
Default Re: Is the flow turbulent?
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Katarina Tenti
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Hello Khalid,

thank you, I checked out the AIAA paper, and am now waiting for the book to arrive.

Cheers, Katarina
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