How Wings Create Lift (Bernoulli's principle stands corrected.)

DugT

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Wings turn flow. The old high pressure vs low pressure explanation of how wings work isn't very accurate. This video is a much better explanation. The physics and semantics of this are still debated but I think this video agrees with an overly complex math and physics based explanation I found at NASA.gov.

Video explaining lift. A video is worth 1000 equations.

NASA complex details
= Equations
 
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dogmeat

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once the air has "turned" behind the trailing edge of the wing there is no part of the aircraft for it to react against, so part of what he is saying is BS. there is also a plate reaction though, air deflected downward by the bottom of the wing

1642274345346.png
 

AAT65

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once the air has "turned" behind the trailing edge of the wing there is no part of the aircraft for it to react against, so part of what he is saying is BS. there is also a plate reaction though, air deflected downward by the bottom of the wing

View attachment 940461 it
I'm not sure it's BS, but the video doesn't explain this very well IMHO (perhaps because the guy who made it says himself he's not a physicist...). The act of turning the airflow by the aerofoil, however it's accomplished, will produce lift. The air is pushed downwards, therefore the wing is pushed upwards: that's Newton's Third Law in action. Having been deflected the airflow carries on in its new direction because there is no more force on it once it has passed the wing: that's Newton's First Law.
I'd also point out that the Bernoulli's Law explanation isn't discounted by this video, just supplemented. Rather than being inaccurate it is incomplete.
 

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once the air has "turned" behind the trailing edge of the wing there is no part of the aircraft for it to react against, so part of what he is saying is BS. there is also a plate reaction though, air deflected downward by the bottom of the wing

dogmeat, you are spot on. There's action but no opportunity for reaction. Once the laminar airflow separates from the airfoil surface, it has no effect whatsoever on the airfoil.

He also mentions how the airflow under the wing slows down. No--it does not appreciably slow down.

This "turning" argument has been floating around for several years. The way it's explained, it appears to function similarly to an engine mounted atop the wing, blowing air backward and downward off the rear of the wing. There are aircraft that do use this engine mounting scheme, and it does generate extra lift...but this is not that.

Drag created by laminar flow over the upper airfoil surface generates lift by greatly reducing air pressure over the back portion of the wing just ahead of the trailing edge. This is the reason why many modern wings incorporate vortex generators--to allow the boundary layer to slip over the surface faster, increasing the lift component and efficiency of the wing.

Dynamic lift certainly is generated by increasing angle of attack.

wing-with-vortex-generators.jpg
 
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Killing Floor

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WOW!!! LOVE THIS!!!

First, in 1999 I entered a research project that was funded by the Navy. We tested aircraft models in a wind tunnel, well actually it was just wings on a cylinder frame. But we applied electric resistance heaters to the upper surface of the wings. The hypothesis was that heated surface = reduced friction, therefore, greater lift.
So kudos to NASA.

I studied a lot of gas and fluid dynamics including aero. I kindly submit that I am a smart aleck. BUT... Science is the original good ole boys network. Think about it. In school, wings need to be tear shaped to support lift, but stick a credit card out the window of your car, what happens? Duh. And before you say "blah, blah, thrust something, my physics teacher said lalala..." remember that supersonic jets must (must) have flat wings, not teardrop. Because blunted wings would not survive the sonic boom events under normal use. And yet supersonic jets don't take of at Mach, they take of at speeds around 200 mi/h, about 30% of Mach 1. So either physicists were wrong, supersonic jets (and rockets) are magic, or we jsut learned something but kept our mouths shut to save the cost of new textbooks.

I love physics in a weird way. I am an engineer. But sometimes science is just the biggest voice drowning out dissent. Pluto is not a planet therefore our solar system isn't in mass balance, therefore there must be a mysterious 9th superplanet that we can't find with the same telescopes that can now trace to the beginning of time. Every hypothesis is either laughed at or fully believed until it becomes a proof.
 

Peegoo

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Because blunted wings would not survive the sonic boom events under normal use.

Air acts like a fluid over an airfoil...but unlike a fluid--being a gas--it is compressible. This is the reason why +Mach airfoils generally are double wedge designs, because the shock wave travels backward over the airfoil as speed increases above Mach. Managing this compressibility problem is also a factor in jet engines, where airflow over Mach disrupts airflow through turbine blades.
 

Killing Floor

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Air acts like a fluid over an airfoil...but unlike a fluid--being a gas--it is compressible. This is the reason why +Mach airfoils generally are double wedge designs, because the shock wave travels backward over the airfoil as speed increases above Mach. Managing this compressibility problem is also a factor in jet engines, where airflow over Mach disrupts airflow through turbine blades.
Which is also why the nozzle shape is compress-expand. Just an observation that there is stubbornness in the way knowledge moves between theory and application.
 

Oxidao

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I didn't research yet this NASA supposed news, but based on my Fluid Dynamics (Aerodynamics) Boomer student books, I think this is a good simplification of the forces involved on Lift, with a couple of 'attention getter' statements.
He's not really denying that Bernouille explains Lift, but he's just adding another factor related.

He says that Lift is not ONLY created because of the "longer path" above the wing (due to its asymmetric profile), which increases the Speed in the upper side, and consequently decreases the Pressure up there, sucking the wing up. Bernouille

The "longer path" thing is a user-friendly simil, for not getting deeper on the Physics related. Which really is "The Magnus effect".
The rest of the info is almost all accurate to me. Just a couple of details.

- Spoilers and Air Brakes/Speed Brakes are the same surfaces used in different forms (both wings at the same time, or alternatively) and situations (Air or Ground), and they produce an small vibration only as SPD BRK's or AIR BRK's, not as SPOILERS, when you only deflect them on one wing OR the other, to brake Lift on that wing and cause ROLL. They progressively take comand of the Roll movement replacing ailerons as speed increases.

There are forces involved down after the wing affecting the aircraft, but more related to: Producing induced DRAG, not Lift
Of the different types of Drag involved (Parasite and Induced), the Induced is generated strictly by means of the Lift created.
 

trev333

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If it creates lift an we can fly then the physics are unnecessary to me.
The physics behind it didn't bother the OZ inhabitants either.... when they invented the aerofoil shape for their boomerangs maybe 50,000 yrs ago...with stone tools... they knew...

shame there were no patent offices open back then....:lol:


boomerang.jpg
 

Oxidao

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once the air has "turned" behind the trailing edge of the wing there is no part of the aircraft for it to react against, so part of what he is saying is BS. there is also a plate reaction though, air deflected downward by the bottom of the wing

View attachment 940461
I think he mixed concepts between DRAG (induced) and LIFT.

IMO That diagram hardly applies to a wing foil.

If that Cessna is yours... You are a lucky Man!
 

Peegoo

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The physics behind it didn't bother the OZ inhabitants either.... when they invented the aerofoil shape for their boomerangs maybe 50,000 yrs ago...with stone tools... they knew...

shame there were no patent offices open back then....:lol:

Heck yes. They learned about this from examining the shape of birds' wings. Otto Lilienthal and Orville and Wilbur Wright used the same approach many years later. The Wrights were the first to build a wind tunnel to test their airfoil shapes in a laboratory environment. Yeah, it was the back room of their bicycle shop, but who's counting Erlenmeyer flasks? ⚗️
 

trev333

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I guess the ancient aussies didn't want to be Birds.... they wanted to catch birds to eat...usually over water...

they didn't want to lose their precious tools across the river after a throw... crocs and all...otherwise they'd just throw rocks or ordinary sticks with less success... they needed the hovering circle shape over head to work.

the returning boomerangs scared the birds off the water, thinking they were eagles/hawks above...into nets slung across the water way in the low flight path of the startled birds.. geese/ducks, etc..,
 

Flyboy

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WOW!!! LOVE THIS!!!

First, in 1999 I entered a research project that was funded by the Navy. We tested aircraft models in a wind tunnel, well actually it was just wings on a cylinder frame. But we applied electric resistance heaters to the upper surface of the wings. The hypothesis was that heated surface = reduced friction, therefore, greater lift.
So kudos to NASA.

I studied a lot of gas and fluid dynamics including aero. I kindly submit that I am a smart aleck. BUT... Science is the original good ole boys network. Think about it. In school, wings need to be tear shaped to support lift, but stick a credit card out the window of your car, what happens? Duh. And before you say "blah, blah, thrust something, my physics teacher said lalala..." remember that supersonic jets must (must) have flat wings, not teardrop. Because blunted wings would not survive the sonic boom events under normal use. And yet supersonic jets don't take of at Mach, they take of at speeds around 200 mi/h, about 30% of Mach 1. So either physicists were wrong, supersonic jets (and rockets) are magic, or we jsut learned something but kept our mouths shut to save the cost of new textbooks.

I love physics in a weird way. I am an engineer. But sometimes science is just the biggest voice drowning out dissent. Pluto is not a planet therefore our solar system isn't in mass balance, therefore there must be a mysterious 9th superplanet that we can't find with the same telescopes that can now trace to the beginning of time. Every hypothesis is either laughed at or fully believed until it becomes a proof.
Can you expand on your penultimate sentence in your final paragraph, please?
 




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