måndag 13 augusti 2012

Teaching Teachers to Not Understand Flight

Jefferson Lab educates teachers about How Airplanes Fly in a video-lecture by Scott Eberhardt, Associate Fellow of AIAA, introduced as follows
  • Did you ever wonder how a Boeing 747, weighing 910,000 lbs at takeoff can possibly get off the ground? 
  • What makes a wing efficient? 
  • These questions can be answered when lift is developed in terms of Newton's laws. 
  • A Newtonian description of lift gives an intuitive feel for how airplanes fly, without the need for complicated analysis or approximations. 
  • Through the application of Newton's three laws, we will develop the role of the angle of attack, the power curve and an understanding of wing efficiency. 
  • You will gain insight into conclusions of classical aerodynamics without the need for analysis.
  • The next time you are on an airplane, you will understand how and why the wing is able to carry such a large load.
Eberhardt tells the teachers/students (with my comments in parenthesis): 
  • I am using a Newtonian description of flight? (What else?)
  • There are things you learned that might be wrong. (What about the present message?)
  • There are different explanations of flight:
  • 1. Mathematical, taught to aeronautical engineers.
  • 2. Popular, taught at flight schools, NASA, in many cases fine but wrong.
  • 3. Physical, presented by myself in this lecture. (Why different explanations if there is one correct?)
  • Lift is a reaction force, single most important thing to remember from this lecture. (Triviality.)
  • The wing pulls air down: downwash. 
  • Why does the air follow the top surface of the wing?
  • What if it didn't? Vaccum!
  • Can't have vacuum. Air is pulled down to fill the vacuum. (Separation? Stall?)
  • Take a cup, stick it under the faucet, se how it sticks to the surface. (So-called Coanda effect?)
This description is as empty as saying that lift comes from lower pressure on top without explaining why the pressure is lower. Here lift is supposed to come from pushing air down, without explaining why air is pushed down except by a vacuous statement about Natures Abhorrence of Vacuum.

If this is the highest scientific insight of a Fellow of AIAA, no wonder that AIAA cannot understand the correct explanation of generation we present in the New Theory of Flight, and thus rejects it.

Compare with my 2009 Interview with Eberhardt. Notice that Eberhardt does not in the above lecture repeat the 2009 message that the air follows the top surface by "stickiness" from viscosity, also referred to
in the 2001 Discover article The Physics of ... Airplanes:
  • Eberhardt stresses that there is no new physics in the book. To understand lift you need only Newton's three laws and something called the Coanda effect. The Coanda effect is just the tendency of air or any even slightly viscous fluid to stick to a surface it is flowing over, and thus to follow the surface as it bends. As air follows the upper surface of a wing, it gets bent downward— because the surface is curved but also because the leading edge is tilted up (especially when ascending) at what is called the angle of attack. The air that is bent downward pulls on the air above it, distending it and creating a low-pressure zone. 
I questioned the "stickiness by viscosity" in the interview, and so Eberhardt maybe picked up something...

Inga kommentarer:

Skicka en kommentar