Hey, so I asked Steve Pomroy... and he offered a fantastic explanation.
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Hey Mario.
If you recall, I talked previously about the importance of distinguishing between the *reason* the air travels faster over the top of the wing, and the *result* of the air traveling faster. Frank's misunderstanding is the result of people not making this distinction. He referenced the "equal transit time" principle, which is indeed garbage. But this is distinct from Bernoulli.REASON: The air travels faster over the top of the wing because of continuity (or circulation if you prefer).
RESULT: Once the increase in speed is a given, Bernoulli dictates a drop in pressure.
The effects of continuity (or circulation) can be both calculated and measured -- and indeed the calculations match the measurements. Ditto for Bernoulli.
Also, Bernoulli's equation can be formally derived from Newton's 2nd Law. It's not possible for one of them to be right while the other is wrong. I won't torture you with the details (calculus), but here's the general process:
1) Select a small element of fluid (air) travelling along a defined streamline.
2) Apply a force balance (Newton's 2nd Law, F=ma) to the fluid element.
3) Integrate (add up) the pressure and velocity changes along the streamline.
4) Result: Bernoulli's Equation (Ps + Pd = C).
For more details:
- http://www.flightwriter.com/2010/12/straw-man-of-equal-transit-time-lift.html
- http://www.flightwriter.com/2010/12/wherefore-art-thou-lift-lift-part-2.html
- http://www.flightwriter.com/2010/12/going-in-circles-lift-part-3.html
Cheers,
Steve Pomroy
President: SkyWriters Publishing
http://www.SkyWriters.aero
http://www.FlightWriter.com
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Happy Flying! Mario.