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Old   July 22, 2008, 10:25
Default Transition Gamma Model
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Gilles
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Hello ! I'm trying to run a simulation of a 3d wing in a wind tunnel. The wing has a NACA4418 profile and a rounded tip. I tried to used the gamma-theta transition model and even I have a y+<1, there is a recirculation zone on the upper surface of the wing. I suspect a numerical error. With a standard SST there is no recirculation so I would like to try the gamma model. This one needs the transition onset Reynolds number as an input. Do somebody know which value do I have to input ? Or do you have any idea ?

That would be very helpful !

Thanks

Gilles
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Old   July 23, 2008, 22:56
Default Re: Transition Gamma Model
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Glenn Horrocks
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Hi,

Why do you say the recirculation is an error? A laminar separation bubble is very common on airfoils. Check the turbulence intermittency - if the flow is laminar going into the separation and turbulent going out then it is likely to be real and a laminar separation bubble.

The normal SST model cannot capture this detail as it assumes the entire flow is turbulent, but you need laminar flow to get the separation started.

Glenn Horrocks
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Old   July 24, 2008, 09:53
Default Re: Transition Gamma Model
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Gilles
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Thanks for the answer Glenn,

Last question, is it possible that my recirculation bubble appears at 0 angle of attack ?
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Old   July 24, 2008, 21:59
Default Re: Transition Gamma Model
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Glenn Horrocks
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Yes.
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