references: content-type: text/plain; charset=us-ascii organization: NASA Langley Research Center, Hampton, VA USA x-url: news:DMt21G.Fos@eskimo.com mime-version: 1.0 newsgroups: rec.models.rc.air x-mailer: Mozilla 1.1 (X11; U; SunOS 4.1.3 sun4) billbeskimo.com (William Beaty) wrote: > >It is perfectly acceptable to totally ignore Bernoulli's law and instead >explain aerodynamic lifting force in terms of Newton's 3rd Law: a wing >applies downward force to the air, the air reacts to the wing, the air is >deflected downwards, and the wing experiences lift. Why must the upper >wing surface be curved differently than the lower? To guarantee >attachment of the airflow via Coanda effect, to prevent stall in other >words. No? > Many people have the mistaken belief that all lift is created by deflecting air downward to generate downwash. Downwash is a by-product of lift created by the tip vortices on a wing rather than the generator of lift. Airfoils, which we all know lift rather well, generate NO net downwash whatsoever. Just as much air is turned upward in front of an airfoil as downward behind an airfoil. It is in fact the pressure differences caused by circulation which generate lift on both airfoils and wings. And for those who refuse to believe that lift can exist without imparting a downward momentum to the air, look at the case of an airship. In that case, lift is created by the bouyant force which results from the difference in pressure between the bottom and top of the airship. No air is deflected, but because you have higher pressure near the bottom and lower pressure near the top, you get lift. This is not to say that imparting momentum to a body of air WON'T generate a force. Of course it will. But this isn't primarily responsible for the generator of lift on wings and airfoils. -------------------------------------------------------------------- Jay D. Hardin (jhardin@avd00.larc.nasa.gov) Lockheed Martin NASA Langley Research Center -------------------------------------------------------------------- _________________________________________________________________ [ Home ] - [ Search ] - [ Contacts ] - [ Help ] _________________________________________________________________