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

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

I don't think he has a thesis yet since he hasn't taken his oral qualifiers......

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.

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

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

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.

Are other people permitted to answer

Not until he gives up : )

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?

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.

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

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

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

i guess it is because of the subsonic region at the nose of the blunt body

Hey no answers from the Peanut Gallery!!!! : )

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.

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.

So have you found an answer to my question and the questions posed by the others?

I think he's given up. Shall we go for answers from others ? or may be Peter give us ans.