How Airplanes Fly: A Physical Description of Lift (1999)
allstar.fiu.edu
allstar.fiu.edu
Specifically in ch 3 he talks about airfoils, airflow, and circulation:
It should be pointed out that your link contradicts the op in places, in particular Denkar says that the role of the Coanda effect in producing lift is a "fairytale" where the op calls it out to explain the lift on the upper airfoil surface (and I have seen this elsewhere as well.)
I hadn't known until recently just how religiously contentious this topic could get.
Maybe it's robust _because_ it was built in 1999, where nobody felt an obligation to add fancy scripts to a text document ;-)
(The current trend of font size inflation is incredibly frustrating because it makes it impossible to configure a browser such that old and new sites are both readable; I have to blame it partly on designers with large screens not setting their DPI appropriately and partly on web browsers not adjusting their default stylesheets for modern screen sizes)
It's incomprehensible to the layman because there is an extreme economy of transmitted data. To decode it you have to know a fairly large vocabulary of domain specific symbols and do some computations to retrieve the correct wind speed and direction, which are encoded.
This is so you can always get your weather, one byte at a time if needed.
KDEN 101353Z 33009KT 10SM FEW080 FEW180 FEW220 04/M09 A2985 RMK AO2 SLP079 T00441089
Also I don't buy that viscosity argument - viscosity diverts air not down - but vertically. The move down is simple dynamics:
.\
the dot is th air particle - the \ is the wing - when the wing moves the dot is forced down under the wing. The particle moves - and so it gets momentum down. The particle touching the wing is moved by the wing (the wing pushes it down - and the particle pushes it up according to the third law - generating the lift), the other particles are pushed by the particles toughing the lift.
This creates a low pressure area behind the wing. But, that low pressure is still pushing down. It just pushes less than the normal air pressure under a wing.
You can see this by dropping a single sheet of paper vs a stack of paper. In your model the low pressure above the wing pulls the paper up slowing it's decent. But, if you drop a stack of loose printer paper the top piece falls as fast as the bottom and is not pulled from the stack.
http://www.physics.rutgers.edu/ugrad/387/388s06/UHV_LEED/UHV...
https://en.wikipedia.org/wiki/Superfluid_helium-4
Viscosity is weird.
(I got a little bit lost in the discussion of upwash. It seemed to me that the idea was upwash was less efficient at moving air than downwash, and therefore more air was moved down.)
Drop a piece of paper and it drifts slowly. Drop a book and it falls fast. In your model the paper is supported by the air below and pulled up by the void behind it.
However, if you put a piece of paper behind a book it sticks to it and is not pulled up. Thus, all lift comes from the bottom. Edit: You can do the same thing with a piece of paper on top of a wing.
PS: The same is true if you pick up a piece of paper with a vacuum. Even if it seems like the suction is providing lift all the force is from outside air.
NASA explains why the "skipping stone" theory of lift is incorrect well [1]. In summary, the upper surface does generate lift.
Do you think individual air molecules are going to magically hold the top of the wing and pull?
Now, you can use an inaccurate model of what's going on. And mathematically it looks like the top of a wing provides lift. But, physically that's not what is happening.
PS: This is only an issue, because we think an aircraft as zero forces acting on it when it's sitting still on a runway. Instead of being under ~2100 pounds of force per square foot on all sides from air.
If you use a suction cup to lift a piece of horizontal glass, well, I think most reasonable people would say it contributes a force. Maybe you'd say no it doesn't, you don't actually lift it, you just provide a lower pressure at the top allowing the bottom air pressure to push it up... Well duh, of course.
PS: Can you point to where you think I changed definitions? I may have been less than clear.
If an aircraft that weighs 1000 kg flies level, then the lift has to be 9800 newtons.
That means the lift is the sum of the effect from both the bottom overpressure and the top underpressure.
You can check it from any dictionary.
If you owe 2000$ and have 2200$ your net worth is positive 200$. But, people don't talk about debt as adding to your net worth even if it's part of the equation debt is reducing the result not increasing it.
PS: I agree you don't need to model the 2.1 tons per square foot of force in most situations. But, just because you ignore something does not mean it goes away.
https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/lift...
Most non-aerobatic wings are asymmetrical because it produces lift at zero angle of attack, and also because it results in a lower stall speed.
Well, apparently that is it! That also explains why planes don't slam into the ground when flying upside down.
Body, gas including, temperature equals energy, total energy is the sum of kinetic and potential energy and potential energy is what bumps into other objects and pushes that away. The faster the gas flows, the more kinetic energy there is, the less potential is left, thus the object is pushed with lower force. If an object shaped such that gas around opposing faces flows in different speeds moves through the gas, opposing faces are pushed with different force and you get lift. The higher the speed, the more total energy is converted to kinetic energy, the less potential energy is left, the higher the force differential. Thus, the faster the object goes, the more lift it generates. That explains minimal take-off speed of an airplane.
This is by no means scientifically rock solid, but gives really good layman explanation.