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Transition prediction, new CFD-Wiki chapter

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Old   April 28, 2007, 14:18
Default Transition prediction, new CFD-Wiki chapter
  #1
Jonas Larsson
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I wrote a small chapter about transition predictions in the Best practise guidlines for turbomachinery in CFD-Wiki.

You can find what I wrote here:

http://www.cfd-online.com/Wiki/Best_...ion_prediction

Do you agree with this? Did I miss anything important?
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Old   April 30, 2007, 09:34
Default Re: Transition prediction, new CFD-Wiki chapter
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Mani
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I find the following statements interesting in combination:

>Predicting natural transition in a pure CFD code is not possible. Predicting by-pass transition in a pure CFD code is almost impossible,...

>For some turbomachinery applications, ..., transition is critical.

That kind of puts in a really bad spot, doesn't it? So that means you need to rely on empiricism?
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Old   April 30, 2007, 09:56
Default Re: Transition prediction, new CFD-Wiki chapter
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Jonas Larsson
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Yep, transition is important in for example modern high-lift low-pressure turbines and predicting transition requires experimental validation and ad-hoc models that have been tuned for similar applications. At least that is my view of it, but I have not designed a new low-pressure turbine myself. Are there any people who have designed a modern high-lift LP turbine who can confirm that special tuned ad-hoc models are used to predict transition?
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Old   April 30, 2007, 10:12
Default Re: Transition prediction, new CFD-Wiki chapter
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ag
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I have been reviewing a report by Zaki and Durbin ("Continuous Mode Interaction and the Bypass Route to Transition", No. TF-97, 2005) that contains one of the best descriptions of the various mechanisms in transition, along with their work to model bypass transition. While your Wiki article is good, I would recommend the report by Z&D as a good reference. If I had an electronic version I'd send you a copy, but unfortunately all I have is a paper version.
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Old   April 30, 2007, 14:52
Default Re: Transition prediction, new CFD-Wiki chapter
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Jonas Larsson
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Is this the same paper as the JFM paper given below?

Zaki, T.A., & Durbin, P.A. (2005) Mode interaction and the bypass route to transition, J. Fluid Mech., 531, pp 85"111

They also have another JFM paper:

Zaki, T.A., & Durbin, P.A. (2006) Continuous mode transition and the effects of pressure gradient, J. Fluid Mech., 563, pp 357-388
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Old   April 30, 2007, 15:25
Default Re: Transition prediction, new CFD-Wiki chapter
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ag
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Not sure - the one I have is a 120-page report presented at an NSF meeting that a co-worker attended. I haven't looked at the two listed, but I would bet that they cover very similar material. It may be that the core results were presented in the JFM, while the report has the results and more background material. I'll have to wander over to the tech library and check out those articles.
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Old   April 30, 2007, 15:29
Default Re: Transition prediction, new CFD-Wiki chapter
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Jonas Larsson
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Refering a long internal report isn't very good since few people will have access to it. A JFM paper would be a much better reference.
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