- #1
stevepm
- 3
- 0
Hello, I have recently joined with hope that I can find a straight forward answer to a question that has bugged me for so long. Why do air foils REALLY produce lift? I have heard and read of the most common explanation involving the bernoulli effect, but when I dug deeper I read that the bernoulli effect does not generate nearly enough lift for an airplane to fly, and that it partially relies on the theory of equal transit times. I also read that the bernoulli effect neglects density or pressure changes expressed in the ideal gas law. Every article or excerpt I read said that the upper body of air as no reason to reach the tail of the wing at the same time as the lower body, and after watching wind tunnel tests, I found this to be true, in fact, the upper body passed its lower counterpart. Now, even though the bernoulli effect does speed up the body of air above the wing slightly, the pressure difference is simply not enough, this is where I ran into a simpler explanation involving the redirection of air, Newtons Third Law, and the Coanda effect. That explanation said that with the redirection of air following the top of the foil by the Coanda effect, combined with the redirection of air off the bottom of the wing, then that would create downwash and take advantage of Newtons third law. THEN I read of the Kutto-Joukowski Theorem, which seemed to use downwash as a source of lift but then it began to mention Bernoulli, but if there are such large holes in the Bernoulli principle, then why is it still used? I apologize for such a lengthy question, but there are simply so many different answers which point to different reasons for support. So, is lift on an airfoil a combination of these theories/laws, is it one of them, or is there something I have not yet stumbled upon?