[Post] [Email Reply] _________________________________________________________________ Re: Controversial From: ah596@FreeNet.Carleton.CA (Max Feil) Date: 1996/01/24 MessageID: DLo9Av.14H@freenet.carleton.ca#4/4 Segment 4 of 4 (Get Previous Article Segment) (Get All 4 Article Segments) _________________________________________________________________ Note that explanations of lift based on Bernoulli (speed vs. pressure) and those based on Newton's Laws (action-reaction from air redirected down) are really much the same. The Bernoulli equation is just the integral form of the momentum equation (F=mA). Therefore it is not correct to say, as many do, that "not all of lift is explained by Bernoulli's principle". Newton's laws and Bernoulli's principle are physical laws that coexist quite nicely, each describing aspects of what is happening as air flows past a wing. Bernoulli's principle can be used to explain 100% of lift, as long as incorrect reasons for speed changes are not stated first! Finally, it is worth mentioning that the way the top of a wing produces lift is the same as the way the bottom of a wing produces lift. Many other explanations separate the two into "Bernoulli/venturi" lift for the top and "air deflection" lift for the bottom, whereas in reality the air simply curves along either surface in a very similar manner. Bernoulli's principle applies fully in both cases. The air going over the top will speed up as it enters the lower pressure region, and the air going under the wing will slow down as it enters the higher pressure region. The top of the wing ends up being the better lift producer, usually producing about twice as much lift as the bottom of the wing. There, that's it. For more detailed information and some discussions on the ideas I have presented above, consult the Sci.aeronautics archives on this subject, some of which are available from me. In my next article I plan to talk about what goes into determining the correct center of gravity for an airplane, which may help you figure out where to place the CG on that radical new and odd-looking design you're working on! Cheers! Max -- Max Feil ah596@freenet.carleton.ca Ottawa, Canada. _________________________________________________________________ [ HOME ] - [ HELP ] - [ CONTACTS ] - [ SEARCH ]