We then have to ask how a flat wing like that of a paper airplane, with no curves anywhere, can generate lift. Note that the flat wing has been drawn at a tilt, this tilt is called "angle of attack" and is necessary for the flat wing to generate lift. The topic of angle of attack will be returned to presently.
later
It is easy, based on the Coanda effect, to visualize why angle of attack (the fore-and-aft tilt of the wing, as illustrated earlier) is crucially important to a symmetrical airfoil, why planes can fly inverted, why flat and thin wings work, and why Experiment 1 with its convex and concave strips of paper works as it does.
and then in the footnotes
7 - In the 1930's the Romanian aerodynamicist Henri-Marie Coanda(1885-1972) observed that a stream of air (or other fluid) emerging from a nozzle tends to follow a nearby curved or flat surface, if the curvature of the surface or angle the surface makes with the stream is not too sharp.
The essential action of the wing is to divert a stream of air downwards, generating lift and drag in the process. The Coanda effect describes how fluids 'stick' close to surfaces they flow over. The magnitude of this effect is driven by the radius of curvature, angle of incidence etc.
What isn't really covered that well is that the Coanda effect is not essential for a wing to work. Simply having a wing at an angle of attack will divert air downwards and cause lift. The Coanda effect can be used to generate greater amounts of lift [1]
> the Coanda effect is not essential for a wing to work
Indeed. The easiest way to see that is to take a piece of paper about the size of a wallet size check and drop it while giving it a little bit of spin around the long axis. The paper will fly, and the reason it flies is exactly the same as the reason a non-spinning wing flies. See:
We then have to ask how a flat wing like that of a paper airplane, with no curves anywhere, can generate lift. Note that the flat wing has been drawn at a tilt, this tilt is called "angle of attack" and is necessary for the flat wing to generate lift. The topic of angle of attack will be returned to presently.
later
It is easy, based on the Coanda effect, to visualize why angle of attack (the fore-and-aft tilt of the wing, as illustrated earlier) is crucially important to a symmetrical airfoil, why planes can fly inverted, why flat and thin wings work, and why Experiment 1 with its convex and concave strips of paper works as it does.
and then in the footnotes
7 - In the 1930's the Romanian aerodynamicist Henri-Marie Coanda(1885-1972) observed that a stream of air (or other fluid) emerging from a nozzle tends to follow a nearby curved or flat surface, if the curvature of the surface or angle the surface makes with the stream is not too sharp.
The essential action of the wing is to divert a stream of air downwards, generating lift and drag in the process. The Coanda effect describes how fluids 'stick' close to surfaces they flow over. The magnitude of this effect is driven by the radius of curvature, angle of incidence etc.
What isn't really covered that well is that the Coanda effect is not essential for a wing to work. Simply having a wing at an angle of attack will divert air downwards and cause lift. The Coanda effect can be used to generate greater amounts of lift [1]
[1] https://en.wikipedia.org/wiki/Coand%C4%83_effect