why aren't the cross sections of wings shaped like the Sears-Haack body?
>>8196991
Which wings?
>>8196999
airplane wings.
>>8196991
Why should they be?
>>8196991
cos you need top and bottom to be different shapes
>>8197007
That's what he said.
>>8196991
Because they wouldn't generate lift. Don't you think, that plane, that can't fly is pretty fucking useless?
>read some more about the way planes wings work.
Also, the fact, that this shape has low drag, doesn't mean that this shaped wings ( if they were able to generate lift) would behave the same way. There are thousands of engineers working on optimising the shape of planes wings. Don't you think, that someone would come up with it, and tested it before?
>>8197010
Good, so can you imagine any reason why only being the most aerodynamic shape for a given size wouldn't be ideal?
>>8197018
>brainlets getting this mad for no reason
>>8197018
>anything you've thought of others have already
>im sure its been done, just leaf it to the experts
>dont ask questions there are thousands of people how can they be wrong
that kind of mentality is why we had a dark age
>>8197018
>Don't you think, that plane, that can't fly is pretty fucking useless?
b-b-but it satisfies my autistic perfectionist tendencies
>>8197010
That's great if they're just moving along the ground but they need to generate lift otherwise they won't fly. Hence the aerofoil shape.
>>8197026
Is it plausible that a less aerodynamic wing is more sturdy?
>>8197026
Yes. It will, but putting wings at an angle generates turbulences, which generate drag. Planes used to work that way back in the days
>>8197028
sears-haack body shaped wing can still have the same volume as an ordinary wing while being more aerodynamic, so, no.
>>8197031
how does an airfoil create lift?
>>8196991
Sears-Haack minimizes drag, it does not maximize lift.
>>8197046
how does an airfoil create lift?
>>8196991
Wings have the shape they have to generate as much lift as possible. Minimizing air resistance is not the priority.
>>8197068
>Minimizing air resistance is not the priority
It pretty much is. You dont see aircraft cruising with 40 degrees flap do you?
>>8197068
how does an airfoil create lift?
>>8197076
Dark wizards.
>>8197076
The answer to that question is complicated.
It generates lift because the pressure above the wing is lower than below, and that is because the air flows faster on top than on the bottom. Why that is, is basically impossible to explain in any useful way. There is some obscure calculation using some transformations of a circle to analytically show that this is indeed the case, but it's not worth going through it. The air around the wing is a very complex system and to understand what happens you need to go all the way (meaning: The Navier-Stokes equations for compressible fluids). It's a good example of how understanding something in physics can happen on different layers, and sometimes there's a gap between one of those layers created by particularly complex systems. We understand how the particles behave on their own and among each other, we also understand pressure and lift and whatever, but connecting those two can't be done by a person. Look at the brain for another example: We understand somewhat how neurons work, and we understand somehow the human mind, but in between those two layers is that huge gap left open by the complexity of the system. How exactly microscopic phenomena add up into collective/emergent phenomena is always a tough question. Especially when exactly the first becomes latter is a horribly difficult question.
>>8197075
Wings that minimize air resistance won't generate lift (those are contradictory). So obviously, doing that is not the priority. It's more important to generate lift, otherwise the whole thing would be useless.
>>8196991
Put it into XFoil and find out for yourself.
>>8197087
i found this
https://drive.google.com/file/d/0B0JABuFvb_G_MkpBZHJmRGo3UkU/edit
thoughts?
>>8197068
>Wings have the shape they have to generate as much lift as possible
Wrong. Usually the airfoil is designed to maximize lift-to-drag ratio, depending on the type and purpose of the aircraft.
>>8197034
vorticity
>>8197149
>wrong
>let me rephrase exactly what you said
cool
>>8197149
Jesus Christ, you fucking NEETs just exist to contradict on the smallest semantic bullshit, right? I explained twice what exactly I meant by "it's not the priority" now, and you still try to be a smartass about irrelevant shit.
>>8197135
Oh yeah, I heard about that too, someone told me not too long ago. It's kind of irrelevant though as the reasoning there isn't of any quantifiable use anyway.
>>8197163
maximizing lift is not the same thing as maximizing lift-to-drag ratio
>>8197178
>to generate as much lift as possible
>>8196991
A Sears-Haack body is optimized to minize drag. And not even overall drag but just wave-drag, to be precise. A wing is optimized to maximize lift-to-drag ratio within the constraints of the airplane's flight envelope.
You use different wings for different conditions. That wing looks like it's not gonna be too useful at low speed.
>>8197443
yeah, a freshman dropout who never passed a class in physics would know
>>8197464
It was chemistry and I don't see how dropping out of that has any bearing on my aerodynamics knowledge which I gained in my own time 6 years later. You haven't even shown my statement to be wrong. Low speed STOL aircraft needs a highly asymmetric airfoil that gives a high coefficient of lift at low speeds. Why the hell would you use a supersonic airfoil? Totally different flow conditions.
>>8197486
all I see is blah, blah, blah
can't take a serial liar seriously.
>>8197488
But his answer is right though. All I see is saltiness. Did you fail fluids or something? What he said is really obvious, that you can't use the same airfoil for every flow condition.
>>8197092
>XFoil
ma nigga
>>8197486
...the tinfoil hat UFO fag is back
>>8197388
which shape is optimized to minimize subsonic drag?
>>8197715
That's an insufficiently specified question. An infinitesimal small point, like e.g. an electron, surely has the least drag. But real world applications are constrained by the fact that a certain volume that needs to be enclosed to be useful, in almost all cases even with a certain form factor, certain shapes and types of engines to propel the vehicle, etc. The choice of propulsion has repercussions on the vehicle due to their own effect on the air flow, positioning of the engine nacelles on the vehicle, interference drag, cost, reliability, accessibility and all that kind of stuff.
>>8197023
>>8197007
>>8197018
Retards, pick related, lift coefficient vs angle of attack of naca0012 airfoil, it's symmetrical. source: http://airfoiltools.com/airfoil/details?airfoil=n0012-il
Also, you might have learned an incorrect theory: https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html
>>8197778
the common criteria is which shape of certain volume and circumference but i though that was implied already in my question.
sears-haack body is the best for supersonic flight if i understand correctly but what about subsonic.
>>8197779
i do wonder what it is about that shape and why a sears-haack or some other shape wouldn't work.
>>8199224
>the common criteria is which shape of certain volume and circumference but i though that was implied already in my question.
It isn't. Even that depends on the actual volume, because boundary layers don't scale. For a small object, like e.g. a bumble bee, air is a pretty thick, viscuous substance. For a large object, like a human, it's thin with little resistance. So even if the form factor were the same (say a sphere of certain volume needs to be enclosed by the vehicle) the actual size makes a huge difference and leads to different optima. To understand this more thoroughly you should look up what Reynolds numbers are. Pic related shows different drag coefficients of spheres of different Reynolds numbers. So you see equal form doesn't lead to equal drag.
To minimize overall drag the designer must find the minimum of the sum of form drag, skin friction drag, wave drag, lift-induced drag and interference drag. It also matters at which points of the flight envelope the vehicle is anticipated to reside most often, so further optimizations can be undertaken.
>sears-haack body is the best for supersonic flight if i understand correctly
Nope. The Sears-Haack body minimizes wave-drag only. Granted, wave drag is dominating overall drag at supersonic speeds, so the optimum shape is quite near the Sears-Haack body, but still something different. Also, the Sears-Haack body optimization is for speeds of around Mach 1.5-Mach 3. At speeds faster than Mach 3 a Newtonian-derived form is superior to the Sears-Haack derived form, as wind channel experiments have proven.
>>8199321
well lets say that we are talking about an object with the circumference of 1 m and the volume of 0.5 m2 and the speed is 500 km/h what is the shape that produces least drag overall?
>>8199768
*m3
>>8197779
ok youve posted a graph but so what? of course a symmetrical aerofoil doesn't generate lift at 0 AoA whats your point
>>8197010
> because it is the most aerodynamic shape for a given width and volume
only for supersonic flight
>>8196991
Because the point of wings is not to be 'aerodynamic' (which I assume you mean low drag). The point of wings is to have a high coefficient of lift in relation to the drag they produce, and it is not always the case that a low drag object will have a high Cl/Cd. There are other factors for designing a wing also, like the stall speed for example - you want your wing to generate a lot of lift at low speeds. There are other factors that go into designing a wing, and it all depends on what you want out of it really - different spec for a fighter that wants performance and different spec for a small cessna that wants to minimize costs.
>>8199801
do non symmetrical airfoils provide better lift than angled symmetrical ones?
>>8197087
>It generates lift because the pressure above the wing is lower than below, and that is because the air flows faster on top than on the bottom.
Still spreading this bullshit myth, eh?
>>8196991
>The Sears–Haack body is the shape with the lowest theoretical wave drag in supersonic flow, for a given body length and given volume.
>supersonic flow
That's why
>>8199866
The first half was correct.
>>8200387
> college dropout
> capable of understanding aerodynamics
pick one
>>8200387
>1+1=2 so everything I say is correct
>t-the first half is right!
had to be a dropout
>>8200408
>I have a trip
>He's still too dumb to work out which posts are mine and which aren't
