Re: [Phys-l] Bernoulli's Principle

[John Denker <jsd@av8n.com>]

On 12/21/2007 03:00 PM, Robert Cohen wrote in part:

> Suppose you hold a wood board out the car window while driving down the
> road.  If the board is oriented with its plane oriented vertically,

There's a classroom version of this, namely making parachutes
out of paper plates.

By measuring the terminal velocity (and the mass of the system)
you can fairly accurately obtain the coefficient of drag.

If you then want to take it to the next level, you can make
a multi-parachute stack:
  http://www.av8n.com/physics/img48/multi-parachute.png

I predict you will discover that the total drag does not scale
simply in proportion to the number of plates, especially when
the spacing (h) is small.

========

I say again that modeling the drag of a bluff body is much more
complicated than modeling the lift of a wing.  If you're pressed
for time, do wings first, and make sure you get as far as lift
being proportional to circulation before you go off on any tangents.