Bernoulli’s Principle in Flight

Venturis are used in the fuel system of some small piston engines in aircraft. Air flows into the engine through a venturi tube. The air speeds up as it squeezes through the narrowest part of the tube. According to Bernoulli’s

О This diagram shows Bernoulli’s Principle as it applies in a venturi tube (top) and to an airfoil in flight (bottom).

DANIEL BERNOULLI (1700-1782)

Daniel Bernoulli was born in Groningen, a city in the Netherlands in Europe. The Bernoulli family produced a number of outstanding mathematicians, but Daniel is the most famous. After gaining a doctorate in medicine, he became a professor of mathematics at St. Petersburg in Russia in 1725. In 1733, Bernoulli moved to Basel, Switzerland, where his family came from originally. He worked first as a professor of anatomy and botany and then of natural philosophy at the University of Basel. Bernoulli’s great work, a book called Hydrodynamica, was published in 1738.

О Daniel Bernoulli’s Hydrodynamica included a description of Bernoulli’s Principle.

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Principle, the air pressure where the tube narrows falls. The fuel pipe is connected to the venturi at this point. The low air pressure inside the venturi sucks a spray of fuel droplets into the engine along with the air. The part of the engine that does this is called the carburetor.

Bernoulli’s Principle is often used to explain how an aircraft wing produces lift. The air that flows over the curved top of the wing speeds up, and the air pressure there falls. Below the wing, the air pressure increases. Low pressure above the wing and high pressure below it are often said to create the upward force of lift.

In fact, lift is more complex than this. The difference in air pressure does not explain all the lift produced by the wing. The curved shape of a wing and its angle, or tilt, deflects air downward. According to Newton’s third law of motion, to every action there is an equal and opposite reaction. So, deflecting air downward also produces the upward force of lift.

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SEE ALSO:

• Laws of Motion • Lift and Drag

• Newton, Isaac • Pressure • Wing

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