9/29/2009

Bernoulli Breezeball

videoAs you can see in the video, the orange balls are being held up only by air blown out of the tubes on the Bernoulli Breezeball exhibit. By adjusting the direction of the tubes you can pass the balls from one airstream to another and eventually into the hoops at the ends of the table.

How does it work:
Moving air has less pressure (pushing power) than still air. Objects may look as if they are sucked into a stream of moving air but are actually being pushed into the stream by the stronger pressure of the air around the stream. When a ball is placed into an airstream, the air flowing upward hits the bottom of the ball and slows down, generating a region of higher pressure. This high-pressure region of air under the ball holds it up. If you try to pull the ball slowly out of the airstream, the air arcs around the ball and its pressure is decreased. The normal pressure on the other side of the ball pushes it back into the airstream.

Daniel Bernoulli:
The Bernoulli Breezeball exhibit is named for Daniel Bernoulli (1700-1782) who was a member of a Swiss family that boasted several famous mathematicians. Bernoulli applied mathematics to the fields of fluid mechanics and also pioneered mathematics work in probability and statistics. He taught at the University of St. Petersburg and later at the University of Basel where he successively chaired the departments of medicine, metaphysics and natural philosophy. Daniel Bernoulli is best known for 1738 publication Hydrodynamica and for Bernoulli's principle which describes the relationship of the speed of a fluid and its pressure.

Bernoulli's principle and aerodynamics:
Bernoulli's principle can be applied to aerodynamics. Using Bernoulli's principle you can calculate the lift force on an airfoil. Airplane wings utilize an airfoil shape that is curved on the top and flat on the bottom. In motion, air flows faster over the curved surface on the top of an airfoil than under the flat bottom. The faster moving air decreases in pressure so less pressure is being applied to the top of an airplane wing than to the bottom. This difference in pressure creates an upwards lift force. If the speed of the air over and under the wing is known, Bernoulli's equations can be used to calculate the lift force upon the airfoil.

Read more about Bernoulli's Principle applied to aerodynamics at the US Centennial of Flight Commission website.

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