Re: Physics of Flight; circulation and vortices

[John Denker <jsd@MONMOUTH.COM>]

At 12:16 AM 8/14/99 -0700, William Beaty wrote:
> Perhaps it is because of my weak ability to grasp physics concepts, but
> the idea of "circulation" did not help me to understand aircraft until I
> was well past the college level.

Or maybe you weren't taught the concept properly.

Our goal should be to teach better than we were taught.

> I see circulation as a topic more appropriate for post-highschool.

Naaaah.

> To
> fill the intervening years, we can employ the action/reaction paradigm.

Action/reaction is good, but does not by itself explain how wings work,
because it begs the question of how much air is yanked down, and why.

> Even that would be a demanding task for many highschool students, to say
> nothing of 3rd-graders!

1) Try the fluttering-card demo, as presented in
  http://www.monmouth.com/~jsd/how/htm/airfoils.html#fig_flutter
and the surrounding discussion.

Third-graders are quite capable of launching the cards themselves, and
enjoy doing it, and will never forget which direction of circulation is
required.

2) Since most people have never seen a vortex, it may help to demonstrate
one.  Get a big tub of water (the bigger the better) and stir it like
crazy.  A paddle on an electric drill may come in handy.  Chuck up a big
flat auger, and then clamp a flat piece of wood to it to make a bigger
(more effective) paddle.  Try not to drop the drill into the water, and if
you do drop it in, unplug it before fishing it out, and don't re-use it
until it's good and dry.