måndag 13 augusti 2012

Non-Physical Principles of Winged Flight

Gale M. Craig informs us in Physical Principles of Winged Flight that:
  • Popular explanations of how wings work are often erroneous and scientifically unsound. Wrong explanations may be given by well-meaning teachers and others, but false teaching may sometimes be just for convenience. 
  • Many years ago, a famous aerodynamicist, Dr. Theodore Von Karman, instructed his assistant: When you are talking to technically illiterate people you must resort to the plausible falsehood instead of the difficult truth. 
  • Falsehood, whether intentional or not, is still being taught. 
  • Curvature of flow and resulting pressure gradients is the source of lift for heavier than air aerodynamic flight. Description of lift as due to pressure gradients in curvature of above-wing and below-wing flows was given by Otto Lilienthal in his 1889 book titled Birdflight as the Basis of Aviation. 
  • Unfortunately that has been neglected for well over a century in favor of pseudoscientific descriptions. 
  • The recirculation around an airfoil or wing is termed circulation, and is, in classical theory, the cause of faster above-wing flow as compared to below-wing flow. As described by Lanchester (1868-1945) in his 1907 book, Aerodynamics, circulation is essential to lift. 
  • The concept of superimposed circulation may seem a bit abstract but circulation is a real rotational movement that travels through the air with the wings of an airplane in flight. 
This is the classical Kutta-Zhukovsky circulation theory which Craig recounts in Stop Abusing Bernoulli - How Airplanes Really Fly sold by
  • Fallacies of popular aerodynamic teachings based on misapplication of Bernoulli's law are revealed, and more appropriate description of wing operation is presented in terms of Newton's laws.
Falsehood, whether intentional or not, is still being taught, also by Craig, as revealed on The Secret of Flight.

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