## tisdag 25 augusti 2009

### New Flight Theory is Taking Off

Our new theory of flight is starting to get appreciated: Diego Gugliotta, professional teacher of aerodynamics to pilot students, expresses
• I had a look to your Mathematical Theory of Flight, which indeed is very interesting. In my leisure time I'm a glider pilot and I also teach pilot students in aerodynamic. Professionally I'm an engineer educated at Aalborg University (thermodynamics, and a M.Sc. in system engineering).
• After reading your paper I really don't know what to do with my teaching. It is my impression that it is very difficult to know what to rely on when explaining why gliders fly at all , and it's obvious that lesson number one shall be by definition "why does it fly". The last two years I adopted the Newton-Bernoulli approach, combined with Kutta-Zhukovsky's circulation theory, without really knowing how to explain such a circulation. I also experienced, like you also mentioned in your paper, that not even NASA explained the theory of lift.
• Your theory gives sense, and I'm looking to adopt it as the right theory of lift in my teaching, but now to the 1 million question: How do I explain a 17 year old glider pilot student with only basic school education the theory of lift? any good idea?
The reaction of Diego Gugliotta supports our experience that not even NASA can explain why it is possible to fly, as illustrated on my blogs listed under theory of flight including interviews with NASA Glenn Research Center and my flight expert collegues at KTH.

An answer to the question by Diego can be:
• Redirection of the incoming flow down will give a reaction up = lift. The flow gets redirected if it does not separate on the top of the wing before the trailing edge. Separation is only possible at a stagnation point. Since the flow is only slightly viscous and thus slides along the wing surface with small friction, stagnation cannot occur before the trailing edge. Hence there is lift. OK? Note that it is crucial that the flow has small viscosity: You cannot glide in syrup.
• As a further comment you may note that I don't believe aerodynamics are anything for pilots. I believe I should adopt to explain how, and not why:-HOW: It's a fact that there is a differential pressure between the upper and the lower part of a wing. It's a fact, and it's very easy to demonstrate even in a classroom, that differential pressure times area ends up with a force.
• -WHY: It's a fact as well, that Bernoulli holds, and that Newton's 3rd law also holds. However, at least for me, circulation is not a fact, and there is where all my "whys" ends up in nonsense. It doesn't necessarily mean that it doesn't hold. It's just not me the one to disclose this eventual fact, as it requires time, dedication and research; exactly the three parameters you and Johan utilize in your work. You tried to disclose the circulation fact,but in your well documented paper, you ended up rejecting this theory. Yourwork gives sense, and I hope to see soon the reaction of other researchersworking in this field, so they can explain to some one that indeed can work out Euler's equations, the theory of lift. Thank you for your work.
Thanks Diego. I think our new theory can be presented to pilots and can also be understood and appreciated by pilots, because it is a correct understandable theory, and nothing is more practically useful than a correct understandable theory. Right?