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How to set the turbulence length scale?

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Old   February 24, 2006, 02:46
Default How to set the turbulence length scale?
  #1
yflin
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I decided to simulate a case of flow around a circular cylinder at Re 20000. But I'm not sure how to set the value of turbulence length scale. Who can tell me how to set it?

Thanks a lot.

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Old   February 24, 2006, 05:19
Default Re: How to set the turbulence length scale?
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satish
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use k-epsilon model along with segregated solver then there is no need of giving turbulence length scale
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Old   February 24, 2006, 06:04
Default Re: How to set the turbulence length scale?
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Emanuele
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An approximate relationship for turbulent length scale is: l=0.07*L where l is the turbulent length scale and L is the geometric relevant dimension. For your problem in my opinion you should use as geometric relevant dimension the diameter of the cylinder. Hope this helps Regards Emanuele
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Old   February 24, 2006, 07:02
Default Re: How to set the turbulence length scale?
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yflin
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Thanks a lot.
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Old   February 25, 2006, 07:52
Default Re: How to set the turbulence length scale?
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Freeman
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And how is it defined this "relevant lenght"? If we are talking about a flow around an helicopter (or whatever), this lenght would be the total lenght of the helicopter? why could not be the lenght of the rotor helices or any other lenght?

Thanks!
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Old   February 25, 2006, 12:47
Default Re: How to set the turbulence length scale?
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A
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use turbulence intensity and hydraulic diameter to specify turbulence. The following relation is mentioned by FLUENT T.I = 0.16 * Re ** (-1/8)
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Old   February 28, 2006, 18:28
Default Re: How to set the turbulence length scale?
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fred
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The relavant lenght is Diameter of cylinder in this case.

Regards
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