by Dave Jackson

Created on: April 30, 2008   Last Updated: May 05, 2008

If only Daniel Bernoulli and Sir Isaac Newton were alive today. They would have been truly amazed to see an Airbus A380 rise off the runway and climb six miles into the sky. Great scientists as they were, a discussion about who's ideas best explain the spectacle would surely have taken place. What an interesting discussion it would have been. Both men made enormous contributions to science, far beyond aviation. This article will speak for Mr. Bernoulli.

When Daniel Bernoulli died in 1782, heavier than air flight was science fiction. Many prominent scientists of the day claimed it would be a millennium before man would fly, if ever. The most serious research was aimed towards balloon technology. The first wind tunnel was constructed in 1871. Only thirty-two short years later the Wright brothers built an airplane in their bicycle shop and took to the air.

Bernoulli's Principle proved that physics, at least in theory, allowed heavier than air flight. Previous designs based on flapping bird wings provided a dead end for aviation. The concept of a low pressure zone above a fixed wing put thinking on the right track. Applying this principle to the propulsion dilemma, the propeller, guaranteed eventual success. It's widely understood that Bernoulli studied aerodynamics and developed his Principle of Lift to that end. Of course the field did not yet exist. But since the Bernoulli Principle can be applied to any fluid, it has relevance in many fields.

Bernoulli was working on his concept of conservation of energy when he discovered the inverse relationship between pressure and density. When the value of one increases, the other is required to decrease. Applying this relationship to fluids, he proved that a fast moving fluid must have a lower pressure than a slow moving fluid. This was a simple but profound realization and is the part of his principle that we use to describe lift. As air molecules pass over a wing they accelerate, spreading out more thinly. With fewer molecules the pressure becomes lower, just as the inverse relationship predicts.

He published his findings in "Hydrodynamica" in 1738. His father actually tried to steal the work, changing the title slightly. Needless to say, they did not enjoy a good relationship.

Giovanni Venturi's venturi tube was used to demonstrate Bernoulli's Principle. In aviation, a wing is often referred to as a "half venturi". This entire concept is hotly debated in some circles.

A century passed before Ludwig Prandtl continued development

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