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Old   November 24, 2005, 18:04
Default Virtex breakdown
  #1
daniel
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HI, is there anyone who's dealing with vortex breakdown in swirling flows? I have a huge list of doubts and problems, ranging from the numerical computations to analytical and physical issues. Definitely an interlocutor would be ideal for me. Thank you
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Old   November 25, 2005, 00:15
Default Re: Virtex breakdown
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Edward Cruz
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Hi Daniel; I've dealt with vortex breakdown on a delta wing. But's that was in the wind tunnel. And not in CFD. There's plenty of articles around dealing with this area. Look at the mechanisms behind vortex flows and the the vortex breakdown process. That will help you clear up your headaches. However, from your message, I have no idea of your problem. Can you be specific. From what you have said, I have a picture of circular combustion chamber with a vortex generator at the centre axis on the inlet where the flow is somewhat flowing in a curvelike manner. Phew, That a lot of work just setting up the CFD simulation. The meshing construction won't be that easy either. Anyway, there plenty of articles dealing with a similar geometry as I've described. I hope I helped you plenty and happy simulation. -Edward

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Old   November 27, 2005, 01:43
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Tomm
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Your problem is most difficult because so far we understand very litter why vortex breaks. I am studying this for long time. It seems the nolinearity to act on it to lead to the change.

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Old   November 27, 2005, 10:57
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Tian_FB
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Daniel, I think you could refer to Vorticity and Vortex Dynamics(By J.Z. Wu,H.Y.Ma ,M.D.Zhou) .

Regasrds,

Tian_FB
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Old   November 27, 2005, 20:45
Default Re: Virtex breakdown
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Taw
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Dear Tian

I am also keen to understand more aabout on Vortex stretching, etc, and the book you cited looks relevant, however I googled and found out the book is in Chinese, is the English version available, and can you advise the bookstore to purchase from. Thanks, Taw
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Old   November 28, 2005, 21:21
Default Re: Virtex breakdown
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Tian_FB
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Dear taw,

I have sent a private email message about this book to you.
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Old   November 28, 2005, 23:27
Default Re: Virtex breakdown
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Edward Cruz
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I agree, there's 2 types of vortex breakdown, bubble and spiral they are similar in shape in 2D and 3D flows. The nonlinearity is due to the wave-like instabilities in the upstream flow. I think someone has a model but I can't recall the exact paper. And I'm not in the mood to dig up my stuff. sorry. As for that book in this discussion, I borrowed that book in English a while ago. It's good for intro. Dig in the journals in your library that will save you time. The book will just point you into that reference anyway. -Edward
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Old   November 29, 2005, 16:12
Default Re: Virtex breakdown
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Daniel
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I agree , the strong non linearity renders the phenomenon difficult to analyze. But I am even twisted on some basic concepts. I find very fascinating the ideas of vortex bd as a non-linear interaction of waves (mainly Liebovich, Rusak, Chomaz views), and they also correlate better with the bifurcation diagram found at high Reynolds number (the unstable branch would be the travelling "soliton" of Leibovich), however from my simulations I find more convincing the feedback scenario described by Brown and Lopez. I have never fully understood the Benjamin theory.... but what I really can't understand is the connection between the different theories that many papers, very important ones (Beran & Culick, Ruith et al.), remark. They describe the process according to Brown and Lopez, but then easily refer to the critical state of Benjamin! I can't undestand. Anyway, for the time being I simply would like to validate my code. And even this seems to be difficult ( I always have a kind of overstimation of the swirl, and I get a stagnation point even when it's not expected. The question is that most of the numerical test cases available are incompressible. I am using a compressible code and make it run at M=0.25. regards

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