Generic Aero question

[NDR008]

Hi guys, I got an aerodynamics exam next Monday and got stuck on something and was hoping that some expert from F1Technical might help.

I was going over one question we had where we had to find Cl, Cd, and Cm.

Now usually after finding Cl, we would find Cdi (induced) and Cd = Cd0 + Cdi.
But in this case we stopped at Cd = Cd0.

In actual fact we could not calculate Cdi in this particular case because we did not know the AR, span, or area, just the chord length.

Had we known the rest, should I have calculated the induced drag?

Ultimately, the question boils down to:
Cdi is not calculated for an infinite wing or because of the Mach number?

[Ciro Pabón]

I have no idea of aerodynamics, so I throw this just to "call" for more posts.

Perhaps the angle of attack is such that there is no lift? Is the only condition that I believe causes Cd = Cd0.

I really don't think so, but...

[syguy]

I think your reasoning is sound.

Of course in reality infinite span wings don't exist, so all real wings will suffer from induced drag originating from wing tip vortices. To minimize induced drag, wing end plates and winglets are used, such as those on F1 front and rear wings, which try to recover some of the benefits (reduced drag) of the fictional infinite span wing.

So as you said, you can't calculate induced drag for an infinite wing.

[NDR008]

Cheers, and everybody wish me luck for Monday, this is the toughest lecturer we have (a French Professor...)

[manchild]

(a French Professor...)

Alain Prost?

[NDR008]

Someone much worse... more full of himself...
The other day he was bragging about his dad being an engine technician and being able to shift gears without a clutch. And I was like "yeah, I do that everyday coz I am lazy" - and I said it with a friendly attitude.

And he got SO defensive, he was like "Can you do it for 1000miles, without breaking the gearbox". Then I just let it go, he is so damn weird...

[Carlos]

Ahh yes, the mature and knowlesgable are sometimes difficult ; maybe more so the French, who,it is generally agreed, invented both thought and located the centre of the universe, as everything French, but imagine how unendurable it would be, driving with his father, and everytime he shifted without a clutch, for 1000 miles, exclaimed triumphantly, "there, I did it again"

A lecture is perhaps 90 minutes? What a blessing in comparison

Self absorbsion is rather Gaulic and admirable, in small ways
http://query.nytimes.com/gst/fullpage.h ... A96F958260

[NDR008]

He is very smart with impressive history, but he sucks at teaching the basics, i am a part time first year tutor, so I have an idea what the job involves, and when I go through his hand written notes... WOW never seen so many mistakes, and when i ask him about them (with all the humility in the world), he admits something is wrong and says "I can't remember what I was doing there, AHhhh you know I was tired".

The worse and coolest thing is when you ask him something intelligent, he says with his tongue out of his mouth goes "prprprprp, I don't know, what do you think?" you give your educated guess and he says once again "prprprprp, I don't know, maybe"...

I get what he is doing us, trying to make us self dependent, but he sucks at doing it, hehe.

[Ogami musashi]

I just confirm that if in your case the wing is infinite no induced drag is necessary for the calculation just Cd0.

[SZ]

yes yes no induced drag on infinite length wings....

obviously your lecturer isn't stupid enough to write the class a predictable test.

you'd be surprised how many lemmings a sucker punch of a question will catch out.

have a little hope and be thankful he's at least brave enough to write questions that matter - for every student that gets it right he's likely to have to deal with another two complaining that it's a trick question...