Re: [Phys-l] Bernoulli's Principle

[Joseph Bellina <jbellina@saintmarys.edu>]

I don't know if this a related issue, but in the early 20th century,  
at the National Physical Laboratory in Teddington England there was a  
Scaling committee, with included the premier mathematicians and  
physicists of the day, and chair, as I recall by Lord Rayleigh.   
Scaling issue at hand was how to take wind tunnel data from models  
and scale it up so the results applied to real aeroplanes which at  
the time were fond of falling down and killing the pilot.  It was not  
an easy task.

joe

Joseph J. Bellina, Jr. Ph.D.
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556

On Dec 21, 2007, at 7:07 PM, John Denker wrote:

> 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.
>
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