Intelligent Compressed Air: Bernoulli’s Principle


Daniel Bernoulli was a Swiss mathematician and physicist born in 1700. He is most known for the Bernoulli principle, published in his book Hydrodynamica in 1739. The Bernoulli’s principle states that an increase in speed of a fluid will result in a decrease in pressure. As a fluid moves from a wider pipe to a narrow one, the fluid begins to move faster. The given volume of the fluid moving from one point to another over a set amount of time will not change. In order for the same amount of fluid to pass through a smaller orifice, it must speed up. This is displayed quite well in the flow of a river. At wide, open spaces the river flows slowly. In areas that become narrow, for example by a canyon wall, the speed of the river’s flow increases dramatically.

The Bernoulli principle also provides an explanation for the lift that is created on an airplane wing. When air encounters an obstacle (in this case an airplane wing), its path will narrow as it flows around the object. As this stream of air speeds up, some of the energy from the random motion of the air molecules must be converted into energy of the stream’s forward flow. Pressure is created by the random motion of these air molecules. Transferring this energy into the stream flow then results in a drop in the air pressure. An airplane wing is shaped so that the air must move faster over it than under it. This causes the slower moving air underneath to exert more pressure on the wing than the air moving across the top. This is referred to as lift and is what allows an airplane to fly.

Temperatures are beginning to creep back up here in Cincinnati and just last week pitchers and catchers for the Cincinnati Reds reported for Spring Training. They’ll also be watching Bernoulli’s principle in action. The oft-dreaded (for batters, anyway) 12-6 curveball occurs due to the way the pitcher forces the ball to spin. Due to way he grips the ball across the laces and imparts this spinning motion, more air pressure forms on the top of the ball. This causes the bottom of the ball to accelerate downwards, resulting in the phenomenon that drives many baseball players crazy as they swing and miss due to a miscalculation of the ball’s position.


Some of EXAIR’s products also utilize the Bernoulli Principle. As the high-velocity air exits the nozzle of a Super Air Knife, a low pressure area is created that draws in surrounding ambient air at a rate of 40:1. The same also occurs with the Super Air Amplifiers, Adjustable Air Amplifiers, and Air Nozzles. If you’d like to discuss the application of any of our Intelligent Compressed Air Products, give an Application Engineer a call today.

Tyler Daniel
Application Engineer
Twitter: @EXAIR_TD


River image courtesy of Sasori33 via Creative Commons License
Reds image courtesy of Lisa via Creative Commons License

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