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Laminar Zone in Turbulent Simulation

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Old   May 28, 2007, 04:03
Default Laminar Zone in Turbulent Simulation
  #1
Demetrios
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Hi everyone I am modeling a tube which "creates" slugs of air in water. The flow of the water in the tube is turbulent but the flow in the nozzle that feeds the air is laminar. How can i define that the zone that feeds the air is laminar?

many thanks
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Old   May 29, 2007, 02:05
Default Re: Laminar Zone in Turbulent Simulation
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Zamir Rashid
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How do you know that the air feed is laminar flow?
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Old   May 29, 2007, 08:09
Default Re: Laminar Zone in Turbulent Simulation
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Demetiros
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The Re number is below 1000, so it must be laminar
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Old   May 29, 2007, 20:28
Default Re: Laminar Zone in Turbulent Simulation
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Zamir Rashid
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You can turn off turbulance modelling in a specified zone by turning on the 'Laminar Zone' option in the 'Fluid' boundary condition panel. You can also set the turbulent viscosity to be zero via the TUI.

define/ boundary-conditions/fluid

Set Turbulent Viscosity to zero within laminar zone?

if your response is 'Yes', FLUENT will set the production term in the turbulent transport equations and the turbulent viscosity as zero.

Refer to the FLUENT documentation for more info.

Hope that helps.
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Old   May 30, 2007, 07:00
Default Re: Laminar Zone in Turbulent Simulation
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tom
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Normally, the turbulent model will "feel" that the flow is laminar in that zone. Most of turbulent models production terms are based on gradients. in laminar flows, these will be smoother, and then the production reduced. first try to run a turbulent simulation and you should see that the eddy viscosity (or the tke) in your laminar part is far lower than in the turbulent one
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Old   May 31, 2007, 06:40
Default Re: Laminar Zone in Turbulent Simulation
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Demetrios
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i would like to thank both of you. I would like to ask you something else as well. Air is fed by a velocity inlet, and once i have turned viscous on it wants me to iput values for Turbulent Intensity, but as i said before flow is supposed to be laminar. How can make the Velocity Inlet Laminar (not having to input value for Intensity)? many thanks
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Old   June 6, 2007, 10:36
Default Re: Laminar Zone in Turbulent Simulation
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tom
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put a very low intensity. (less than .01%)
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