As you might have inferred from some of the material I have posted over the years, I have been involved in model and, to a lesser extent, full-size aviation for many decades. There has been a long-standing discussion over how lift is produced by an airfoil. Most of us learned that the total lift is a combination of the downward force created by the air moving past and deflecting off the bottom of the wing (equal-and-opposite reaction), and the Bernoulli effect that creates an area of relatively low pressure on the top surface of the airfoil by virtue of the longer airflow path on the curved top surface. NASA, the ESA, and probably all other authoritative sources employ the multiple factor view when calculating lift and other aerodynamic forces.
I am always amazed when someone is willing to put his ignorance - or maybe it is pure arrogance - on display by proclaiming a viewpoint (usually an uneducated opinion) and then implying that anyone who does not sign on is inferior. Then, even when confronted with the truth, those people are often unrelenting.
In the August 2007 edition of the IEEE Spectrum magazine, a reader wrote in to criticize the author of an earlier article for invoking the Bernoulli mechanism of lift generation when, in the reader’s opinion, lift is generated primarily by the equal-and-opposite effect of deflected air. He uses an inverted airfoil as an example of how Bernoulli cannot work. A search of NASA’s website quickly turns up an explanation of how, in fact, it does predict lift for an inverted airfoil due to Bernoulli, provided that the angle of attack is great enough to offset the more curved bottom surface. A fully symmetrical airfoil needs only a small positive angle of attack (AoA) to generate a lot of lift (assuming the wing loading is not excessive). To assign the difference between zero lift at zero degrees AoA and that generated with a couple degrees of positive AoA (great enough to lift a 1,500 lb plane + pilot) primarily to an equal-and-opposite force reaction is nonsensical.
You can read my polite response to the reader as printed in the October 2007 edition. The editors cut out about half of what I wrote, but it gets the point across. I do wish that they had left the last sentence in its original form where I said that the NASA website is replete with examples of Bernoulli, including downloadable software and instruction kits for teachers at all educational levels.
See “Foiled Again” (title given by Spectrum) http://www.spectrum.ieee.org/oct07/5564
Here is the reader’s letter (“Newton, Not Bernoulli”) http://www.spectrum.ieee.org/aug07/5396
Unlike the reader’s claim, I attribute the authority of my position to NASA, not myself.
- Kirt Blattenberger
RF Cafe Progenitor & Webmaster