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turbulence modeling for external aerodynamics

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Old   June 26, 2001, 03:24
Default turbulence modeling for external aerodynamics
  #1
Charles Renard
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Hi !

I would like to know what are the best choices to model turbulence in an external aerodynamics problem around an aotomotive vehicle.

For example which values are commonly taken for turb. intensity, or K , or epsilon, or ....

I noticed we need to define two values in Fluent.

Thanks

Charles
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Old   June 26, 2001, 10:19
Default Re: turbulence modeling for external aerodynamics
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andy
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Unless you have something that sharply defines the separation off the rear of vehicle, do not transport significant levels of k into the stagnation region at the front of the vehicle, etc... I would suggest that the standard k-e model is not a wise choice if a reliable prediction of the flow over a ground vehicle is required.

The value of boundary conditions for k and e is determined by the conditions you wish to simulate: smooth air, gusty conditions, velocity of vehicle, etc... Your question is not answerable without further information.

I would suggest the FLUENT support desk or a local experienced CFD user is probably your best bet for getting you up to speed with understanding this sort of thing.

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Old   June 27, 2001, 03:29
Default Re: turbulence modeling for external aerodynamics
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Charles Renard
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Well I already had a discusion with a Fluent guy and we chose Realizable k-eps for my concern.

i just want to simulate the speed of the vehicle ( about 90 km/h) in "normal conditions".

My needs are the typical values for the definition of turbulence in the entry box for velocity inlet boundary condition.

i hope you will understand a little more

thanks by advance.

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Old   June 27, 2001, 07:55
Default Re: turbulence modeling for external aerodynamics
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andy
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If you are happy with the advice from the FLUENT man then stick with it. What does he suggest you use for your turbulent boundary conditions?

If I were to tell you 42.456576 and 789.345789 would this really get you any further or help with the next problem? Is my advice trustworthy? What aspects of the predicition you are going to get will be reasonable and which will not? (You can be sure your simulation will not get everything 100% correct).

I was trying to suggest previously that you need to tap into a source of information on how to go about performing CFD simulations. Bite sized answers on CFD Online is not really going to provide that.

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