small aerodynamics question

just think you people might know this one


in the co-efficent of lift equation

Cl= 2 W / p v^2 S

what is it that W represents. i think it is weight but im not sure
p(roe) is air density
v velocity
s wing area

its ok w does refer to weight

That equation works for steady level flight. If you're yankin' and bankin', the equation changes slightly from the one you gave. this is because of the G forces increase to equivalent weight... while technically still right (assuming the weight adjusted for the additional G loading) the more accepted version follows below. It's because the wing will provide the lift to lift the airplane and a lot of times planes will do a cruise climb because the weight is everchanging. I'll explain a little more exactly with equations. Anymore aerodynamics questions and I've got you covered, it's practically my job (ok a little more school but hey what can ya do...)

If you're turning in a circle F=m*V^2/R
with F=Lift
V=speed
R=radius of the turn

this is because you've accelerating inward with circles.

L=.5*Cl*V^2*rho*S thus leading to
Cl=2*L/(V^2*rho*S)

[edit on 10-8-2006 by LordOfBunnies]

W is the weight in newtons, it should actually be Lift [which is identical to weight in steady level flight] but thats nitpicking.




Uhm, for manouvering, you'd be safer just using the bank angle.

For a 60 degree bank angle, you are asking the wings to provide 2g of lift.

L = W/[Cos Theta]

Where Theta is the bank angle.

should have shown the whole question i suppose

it was for steady level flight

what course are you doing Lord of bunnies?

there will maybe be more on such things as pressure distribution graphs, and what ever else is hard for me to do or im lazy

I've taken subsonic and supersonic aerodynamics classes. They were technically fluids classes, but we covered a lot of aerodynamic basics in them. This coming semester I'll be doing Computational Fluid Dynamics (CFD) with the following semester being viscous flows. And it will all be good once I get the crap worked out with my advisor. At any rate, I'll try to answer any questions you've got. Hell, the reason I joined this forum was to bring a little more science to it .

Once, I made an adaptive wing. I'm surprised it's not in wide use.

All it is is a material introduced on the backs of the wings that is _supple_. Kind of like a spoiler on a car.

I used vulcanized rubber.

Originally posted by bothered
Once, I made an adaptive wing. I'm surprised it's not in wide use.

All it is is a material introduced on the backs of the wings that is _supple_. Kind of like a spoiler on a car.

I used vulcanized rubber.

By the back of the wing do you mean the trailing edge? Or the suction surface?


I remember reading research the US Navy tried adaptive/flexible surfaces, they were trying to recreate the effects of a dolphins skin, to control boundary layer growth, unsuccessfully I might add.

Originally posted by kilcoo316

Originally posted by bothered
Once, I made an adaptive wing. I'm surprised it's not in wide use.

All it is is a material introduced on the backs of the wings that is _supple_. Kind of like a spoiler on a car.

I used vulcanized rubber.

By the back of the wing do you mean the trailing edge? Or the suction surface?


I remember reading research the US Navy tried adaptive/flexible surfaces, they were trying to recreate the effects of a dolphins skin, to control boundary layer growth, unsuccessfully I might add.

The trailing edge. In Physics I learned you are trying to create two shear planes.
With the latter one adding to the previous, superflously.


--> _____
^^^

Too add, the introduction of a counter balancing current in a blade propelled craft adds lift. Like on a helicopter a counter rotating blade underneath the main shaft will generate stability.

:V___V
: --^--


[edit on 11-8-2006 by bothered]

Originally posted by bothered
The trailing edge. In Physics I learned you are trying to create two shear planes.
With the latter one adding to the previous, superflously.


--> _____
^^^

Well, the performance of an aerofoil is pretty insensitive to the extreme trailing edge geometry to be honest (within reason).

Often its just chopped instead of being rounded for ease of manufacturing.

There is also virtually no pressure differential at the trailing edge, so there would tend to be little deflection of any moveable lip [unless you are using the trailing edge as a form of gurney flap I suppose, then addition lift is generated, at quite a high price in drag].


What kind of figures were you seeing with the modified trailing edge?

I share a lab with some people working on morphing aircraft. They don't change dramatically. This isn't Transformers (Robots in Disguise), but they were doing some cool stuff. The problem with stuff like this is that it has to take load, lots of load. It also has to last a long time with only basic maintenance on the parts. And all those parts to create a morphing wing have to be manufactored creating more expense. Eventually you lose the cost-benefit war and you make a normal flapped/slatted wing. Vulcanized rubber might do some good, but remember this thing is going to be sitting out in the sun and it won't be long before it hardens, cracks, and falls apart. UV tends to do that. I can try to pull up some thesis stuff or the stuff from some profs who're working on it.

Originally posted by kilcoo316

Originally posted by bothered
The trailing edge. In Physics I learned you are trying to create two shear planes.
With the latter one adding to the previous, superflously.


--> _____
^^^

Well, the performance of an aerofoil is pretty insensitive to the extreme trailing edge geometry to be honest (within reason).

Often its just chopped instead of being rounded for ease of manufacturing.

There is also virtually no pressure differential at the trailing edge, so there would tend to be little deflection of any moveable lip [unless you are using the trailing edge as a form of gurney flap I suppose, then addition lift is generated, at quite a high price in drag].


What kind of figures were you seeing with the modified trailing edge?

But then again, don't most paper models do better with tape?

Originally posted by bothered


But then again, don't most paper models do better with tape?

Totally different subject. The tape gives rigidity. It has nothing to do with the profile of the trailing edge of the wing. The trailing edge of the wing (for the majority of the flight regime) is almost inconsequential, as kilcoo stated previously. Area increase during lift-off (and during landing) is about the only time it comes into major play. Aside from that it sits in an adverse pressure gradient and just mainly increases drag.

EDIT: reworded last sentence to convey what I wanted.

[edit on 8-11-2006 by Valhall]

I used to run a fluid dynamics program with theoretical data input.

I'm pretty sure this works. The edge should be raised about 1/2 inch.

I think it's called "dynamic lift".

Originally posted by bothered
I used to run a fluid dynamics program with theoretical data input.

I'm pretty sure this works. The edge should be raised about 1/2 inch.

I think it's called "dynamic lift".

bothered,

Can you sketch a diagram of what you are referring to? I'm having a difficult time understanding the geometry change you are referring to. Thanks!