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Sabatini November 13, 2000 09:35

Mixing length
 
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

Bo Jensen November 16, 2000 06:41

Re: Mixing length
 
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

Sabatini November 17, 2000 06:25

Re: Mixing length
 
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

AK Balasubramanian December 31, 2000 06:08

Re: Mixing length
 
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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