Ok, I stand corrected. Harry William Beaty wrote:
> On Wed, 7 Dec 2005, Harry Veeder wrote: >> >> William Beaty wrote: >>> But I already know the answer. It's simple: Pressure differentials >>> explain 100% of the lifting force, while flow-deflection (the acceleration >>> of fluid masses) also explains 100% of the lifting force. These are >>> simply two independant ways of attacking the problem. There is no >>> competition between a "Bernoulli" viewpoint and a "Newton" viewpoint. >>> This is just another way of saying that the Bernoulli equation ends up >>> obeying Newton's laws. Or in other words, if the water is deflected, >>> there MUST be a pressure differential which causes a lifting force... and >>> if there is a lifting force, then the water MUST be deflected. >> >> I don't think the two explanations are equivalent. >> During level flight the Bernoulli explanation DOES NOT predict that >> the fluid leaving the wing tip will be directed downwards. > > On the contrary, in 3D flight the Bernoulli explanation *requires* that > fluid leaving the wing tip be deflected downwards. That's the reason for > sharp trailing edges, the reason that cambered airfoils give lift at zero > attack, and it's the whole point of the "Kutta Condition." > > But there's also a wrong explanation that wormed its way into many books, > and explanation which depicts the air flowing horizontally off the > trailing edge of an untilted wing. The diagram is wrong, and real wings > only do such a thing when adjusted to give zero lifting force. The > diagrams showing undeflected air are certainly not the "Bernoulli > explanation." The wrong explanation has become known as the "Popular > explanation" or the "equal transit-time fallacy" in order to distinguish > it from the "Bernoulli explanation." > > In other words... since an airfoil always deflects air downwards from its > trailing edge in order to generate a lifting force, then all correct > explanations of airfoil function will include the downward deflection of > air as part of the explanation. > > > (((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))) > William J. Beaty SCIENCE HOBBYIST website > billb at amasci com http://amasci.com > EE/programmer/sci-exhibits amateur science, hobby projects, sci fair > Seattle, WA 206-789-0775 unusual phenomena, tesla coils, weird sci >
