# Oral Qualifying Exam Problems!

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 March 19, 2003, 11:15 Oral Qualifying Exam Problems! #1 Wen Long Guest   Posts: n/a Hi, I'm gonna take the oral exam of PhD qualifying soon, and the difficulity of it cannot be overestimated. Pls feel free to ask questions about general fluid dynamics, you can ask anything, the more the better, the more about physical understanding, the better, for example, Munk asked Elgar a question: how much wave energy is there on this Earth? Then we end up with identifying all kinds of waves, dimensional analysis to estimate the scale of each wave, dissipation rate... very tough and interesting problem. Now, pls, just put all question marks to me. wen

 March 19, 2003, 14:08 Re: Oral Qualifying Exam Problems! #2 Manosh Guest   Posts: n/a Well, Examiners will ask you questions based on your works that you have done. If you read your thesis you can mark youself many questions which will be very helpful for you I think. Good luck Manosh

 March 19, 2003, 14:46 Re: Oral Qualifying Exam Problems! #3 Peter Attar Guest   Posts: n/a I don't think he has a thesis yet since he hasn't taken his oral qualifiers......

 March 19, 2003, 14:52 Re: Oral Qualifying Exam Problems! #4 Peter Attar Guest   Posts: n/a Ok here's an easy one: What is it about the blunt body problem(blunt body moving at supersonic or hypersonic speeds) that makes solving it using a steady solution impossible.

 March 19, 2003, 16:44 Re: Oral Qualifying Exam Problems! #5 Wen Long Guest   Posts: n/a No, I was told that the teachers can ask anything, maybe things without answer, they want to know how I approach a problem So just feel free to ask anything about fluid mechanics, thanks

 March 19, 2003, 16:48 Re: Oral Qualifying Exam Problems! #6 Wen Long Guest   Posts: n/a I would say if the upstream velocity is unsteady, say U(t), then it'll be hard to use steady solution by shifting coordinate system Also even when U is const, if the Reynold number gets bigger, and flow in the wake becomes unstable, then the whole problem is unsteady and can't find a steady solution. wen

 March 19, 2003, 17:03 Re: Oral Qualifying Exam Problems! #7 Peter Attar Guest   Posts: n/a Not quite..think about what happens around a shock wave and how mathematically different subsonic flow is from supersonic flow..this not an easy problem per se..however it is easy in the sense that the problem is a classic one for which a breakthrough was made in the 60's. I won't tell you the answer today..think about it some more and look up some resources(Moretti and Abbett first solved the problem). If you can't figure it out in a couple of days I will give you the answer.

 March 20, 2003, 00:59 Re: Oral Qualifying Exam Problems! #8 Praveen Guest   Posts: n/a Are other people permitted to answer

 March 20, 2003, 08:01 Re: Oral Qualifying Exam Problems! #9 Peter Attar Guest   Posts: n/a Not until he gives up : )

 March 20, 2003, 09:49 Re: Oral Qualifying Exam Problems! #10 John Bradley Guest   Posts: n/a Why do chimneys often have a spiraling pattern of bars on the outside? Why do tea-leafs pile up in the center on the bottom of a tea-cup when you stir it?

 March 20, 2003, 12:47 Re: Oral Qualifying Exam Problems! #11 frank Guest   Posts: n/a Important questions the world was waiting for, are stated by Mr. Bradley. A+. These will enlighten a complete new view on CFD to all of us. Thanks. Frank.

 March 20, 2003, 13:39 Re: Oral Qualifying Exam Problems! #12 Jason Guest   Posts: n/a Rank these in order of difficulty to predict and elaborate on why: laminar separation from a curved surface turbulent separation from a curved surface by-pass transition natural transition skin friction heat transfer pressure distribution total pressure loss

 March 20, 2003, 13:46 Re: Oral Qualifying Exam Problems! #13 Wen Long Guest   Posts: n/a Cool, I'll try to give answer too all question in the next week. Now I'm reading books. Carry on, please, and thanks wen

 March 20, 2003, 17:33 Re: Oral Qualifying Exam Problems! #14 Jan Rusås Guest   Posts: n/a http://www.cfd-online.com/Forum/main....cgi?read=1901 The best is to have the knowledge second best is to know where to find it

 March 20, 2003, 22:50 Re: Oral Qualifying Exam Problems! #15 George Guest   Posts: n/a i guess it is because of the subsonic region at the nose of the blunt body

 March 20, 2003, 23:49 Re: Oral Qualifying Exam Problems! #16 Peter Attar Guest   Posts: n/a Hey no answers from the Peanut Gallery!!!! : )

 March 21, 2003, 12:20 Re: Oral Qualifying Exam Problems! #17 Holidays Guest   Posts: n/a True, but they will ask general topics, followed by an in-depth analysis of YOUR work in which they might not be as expert as you are; therefore they might try to destabilize you, so hold your ground. The Chairman at my oral examination told me in the end that he was indeed looking for a proper scientific argument, and that although he disagreed with me on some issues he had enjoyed the arguing and the fact I could respond and hold a position.

 March 21, 2003, 17:03 Re: Oral Qualifying Exam Problems! #18 Peter Attar Guest   Posts: n/a My point was that in general he doesn't have any real work of yet..at least at Duke quals are held within the first year or two when mostly you are taking classes and just starting your research..the tough questions on your work are usually at the prelims or final PhD defense..but I agree in that they usually just want to see if you can think your way through a problem.

 March 27, 2003, 15:59 Re: Oral Qualifying Exam Problems! #19 Peter Attar Guest   Posts: n/a So have you found an answer to my question and the questions posed by the others?

 March 30, 2003, 14:41 Re: Oral Qualifying Exam Problems! #20 Abhinav Guest   Posts: n/a I think he's given up. Shall we go for answers from others ? or may be Peter give us ans.

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