Questions About Aerodynamics and Flying Cars- Help!


by T.O.E Dream
Tags: aerodynamics, cars, flying
T.O.E Dream
T.O.E Dream is offline
#1
Apr21-09, 08:38 PM
P: 218
Sorry i didn't know where else to ask this so i'm hoping you guys can help anyways.

If a air moving over a wing causes lift then why do planes need to move in order for this to happen. What i mean is instead of moving in order for the air to pass the wing why can't we "blow" air at fast speeds over a wing to create lift. Would this cause verticle lift? Can someone clear things up.

Thanks in advance!
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nasu
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#2
Apr21-09, 09:03 PM
P: 1,904
Sure, you can do this. If you blow air over a wing you create lift.
Danger
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#3
Apr21-09, 09:03 PM
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We can do that very thing, but it doesn't really get you anywhere. If you consider it from a modeling aspect, that's exactly what happens in a wind tunnel. I have also seen an aeroplane (a German Stork) not only take off without moving, but also fly backwards along the runway because the wind was faster than its minimum stall point. (Stall depends upon both angle of attack and speed.)

T.O.E Dream
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#4
Apr21-09, 09:19 PM
P: 218

Questions About Aerodynamics and Flying Cars- Help!


But will it be vertical lift (considering that you measured everything precisely)?
rcgldr
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#5
Apr21-09, 09:28 PM
HW Helper
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Some very overpowered radio control models almost do this due to the prop wash across the wing.
russ_watters
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#6
Apr21-09, 10:54 PM
Mentor
P: 22,001
Note, T.O.E., that if you want this vehicle to actually go anywhere, you also need forward speed...
Phrak
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#7
Apr21-09, 11:18 PM
P: 4,513
This was developed as early as the 50s. (What's the guy's name?...) He built a working prototype where the wing had a channel toward the root of the wing. It was like a dip in the wing with 180 degrees of the propeller wash running through the dip. Significantly greater lift is developed.

Edit: Found it. http://www.scripophily.net/cuschanwinai.html

There's nothing wrong with your idea, TOE. One could concievably develop lift from stationary wings with air blowing over the top in various directions without requiring forward motion. I can imagine a bunch of ducted fans could do it, which can achieve the same results by the same means, and ducted fans can be redirected for forward motion.
T.O.E Dream
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#8
Apr22-09, 04:39 PM
P: 218
Thanks, these were the answers i was looking for!

By the way does anyone know any free wind tunnel simulations on the internet. I know that you can find how much a wing creates lift by an equation. But you need to find it's lift coefficient which you usually do in a wind tunnel. I'm just doing a bit of research.
rcgldr
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#9
Apr22-09, 05:18 PM
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There are free programs like xfoil that might help. xfoil is a dos (or unix) interactive program. It makes some simplifying assumptions, but I've read that it's reasonably accurate for speeds below 1/3 mach.

http://web.mit.edu/drela/Public/web/xfoil
Phrak
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#10
Apr22-09, 06:50 PM
P: 4,513
Theory of Wing Sections, Abbot, a Dover reprint, 1959 isn't bad for getting fairly close design values for wings, if that's what you're interested in. Using various equations and graphs, it will allow you to calculate the lift of a particular foil of some fairly simple wing plane-forms such as elliptical, rectangular, or tapered. But just as with Xfoil, which is for single, isolated sections only, it won't help with interacting systems such as a wing subjected to prop wash. The text is available online as a free downloadable ebook in .pdf, if you jump through some login hoops.


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