## måndag 27 juli 2009

### Fear of Flying?

Are you afraid of flying? If so, you should not read the following, except the very last paragraph. If you are not afraid of flying, and want to know the whole thruth, you should read the following and see if there is any need to change your mind.

Summing up my blog-poll with aerodynamics experts on why it is possible to fly and sail, or how a wing generates lift at small drag, I find that no convincing theory is presented. Either the expert flatly refuses to say anything whatsoever about the basic question of the expert's area of expertize, which is common but a bit disappointing as an expression of expertize, or the expert including NASA presents nonsense-theory such as
• lift comes from the pressure distribution around the wing
• lift comes from downwash
• lift comes from Newton's law
• lift comes form Bernuoilli's law
or refers to a "mathematical" circulation theory stating that
• lift comes from large scale circulation around the wing
• lift comes from wing-tip vortices
• lift comes from a Prandtl lifting line including a starting vortex.
The circulation theory for lift of a wing was suggested by Kutta-Zhukovsky in the beginning of the 20th century as an analog to an earlier circulation theory for the Magnus effect causing a top-spin tennis ball to curve down.

However, according to state-of-the-art fluid dynamics, the Magnus effect results from unsymmetric separation and not from large scale circulation. Likewise, circulation is not the origin of lift of a wing. The failing belief in circulation theory is expressed by the fact that in state-of-the-art it is described as a "mathematical" theory, which means that it is an un-physical theory, which does not correctly describe physics; it is only a "mathematical trick" without physical meaning, see The Spell of Kutta-Zhukovsky's Circulation Theory.

The net result is that according to experts there is no physical theory of flying. Surprised? How do you feel now? No fear of flying even if experts don't know what keeps an airplane in the air?

Should I then cancel my next flight, you ask? No, you don't have to. Take a look at Why It Is Possible to Fly and you will discover an understandable new correct physical theory of lift and drag of a wing. You can take it as medication against fear of flying!