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Old   November 13, 2000, 09:35
Default Mixing length
  #1
Sabatini
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Hay people

i have one rectangular duct 50mm*50mm*4500mm, for the boundary condition at the inlet i have choose the turbulent intensity 5% but the problem what i have how i can choose the turbulent mixing length in the entrance of the duct, have somebody some suggestion or literatur for that Thanks
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Old   November 16, 2000, 06:41
Default Re: Mixing length
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Bo Jensen
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I have seen in manuals for different CFD programs that a fully developed turbulent flow has turbulence intensity of 5% (as you use) and a mixing length of 0.1 times the hydraulic diameter.

Regards

Bo
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Old   November 17, 2000, 06:25
Default Re: Mixing length
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Sabatini
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Hay jensen

you mean 0.1 times the hydraulic diameter is 10% von Hydralic diameter in the entrance( i have a circular entrance von 100mm diameter. thanks
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Old   December 31, 2000, 06:08
Default Re: Mixing length
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AK Balasubramanian
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Hi sabatini,

If the values of the turbulent viscosity are more than one or two orders of magnitude grater than the molecular viscosity, then the you should thoroughly review the assumption and/or data used to calculate turbulence at the boundaries.

Regards,

AK Balasubramanian
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