by James Bowles

Created on: June 12, 2009

I. INTRODUCTION:

If some families were to be stranded on a desolate Pacific isle and wanted to survive and foster the beginnings of a civilization, the best hope would be if they had with them the works of Sir Isaac Newton (the laws of motion, c1687), the works of Faraday (electricity flows from a moving magnetic field, c1821) and the works of Bernoulli (how everything works, c1738)

If we had to choose one - it would be Bernoulli. Bernoulli explains why the front door closes to a Summer breeze, and how the carburetor works on a 55 Chevy. It explains how to design a sailboat to sail into the wind. It explains airfoils, and the propeller on your favorite outboard (and the one used on a Cessna). It explains the vapors seen streaming from the wingtips. It explains the aspirator used by asthma patients; and when the Wright brothers made the first flight from Kitty Hawk, North Carolina, c1903, Orville and Wilbur manned the tiller, while Bernoulli gave the wings lift and the propeller thrust to take the craft 120 feet down field (note 1, 4 and 5).

Bernoulli also explains buoyancy, and in effect, provides the mathematics for Archimedes principle, c200's B.C., (note 2).

And if we were needing to make a waste water purification pond to service this isle civilization, we would enlist Bernoulli to manage the flow between aeration ponds.

But before we go on, we should correct two errors in the title. Bernoulli is not a theory - it is cold hard fact. Neither was it expressed as a theory or hypothesis. Bernoulli's principle was written in the form of an energy equation with essentially four terms: (pressure) + (velocity) + (height potential) + (frictional and turbulence losses)

II. THE EFFECT OF PRESSURE IN BERNOULLI'S PRINCIPLE

Without a doubt - pressure is central to all functional devices that employ Bernoulli's principle (see following discussion).

III. BERNOULLI'S PRINCIPLE:

Bernoulli's principle was stated in equation form as follows:

The energy at any point within an open or closed flowing system = (the contributions from pressure) + (the contributions from velocity) + (potential contributions from height) + (loses from friction and turbulence)

The equation can be written in any manner of styles, but the following style is perhaps more intuitive (note 3). The units are in feet.

1.) e (energy at any point) = (p/gamma) + (v2/2g) + h + f

where: p = pressure, gamma (the Greek letter) = density of the fluid (pounds/cubic foot); v = average velocity;

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