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k-omega model and unsteady transition

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Old   May 4, 1999, 07:47
Default k-omega model and unsteady transition
Jens Thurso
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According to 'Turbulence Modeling for CFD' by D.C.Wilcox, the k-omega model and its low-Reynolds modifications have already been applied to steady transition problems, e.g. flat plate flows. No information is given on the possibility of using the model for unsteady transitional flows, as for example oscillating boundary layer flows. My question is the following: Has anyone made experience with the k-omega model being applied to unsteady transitional flows ? Regards, Jens.
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Old   May 4, 1999, 09:50
Default Re: k-omega model and unsteady transition
Jonas Larsson
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I don't know about unsteady transition. However, I have used different variants of Wilcox's k-omega models (and also many other low-Re k-epsilon models) trying to predict transition on turbine blades.

It is my experience that it is extremely difficult to use this kind of turbulence models to predict by-pass transition in this kind of cases. You can often find papers where this is done though, but I'm convinced that the majority of these results have been tuned in some way.

For flat plate cases (without any kind of leading edge) these models can indeed predict by-pass transition (caused by the diffusion of free-stream turbulence into the boundary layer, ie not a natural transition). I've done this myself. However, as soon as you have a leading edge of some kind things become much more difficult. You can get a lot more information about this from Ercoftac - they had several test cases that dealt with this problem. I think this program was coordinated by Saville.

What kind of application or case are you interested in?
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