Bernoulli's principle

Bernoulli's principle states that in fluid flow, an increase in velocity occurs simultaneously with decrease in pressure. It is named for the Dutch/Swiss mathematician/scientist Daniel Bernoulli, though it was previously understood by Leonhard Euler and others. For a mathematical formulation, see Bernoulli's equation. In a fluid flow with no viscosity, and therefore one in which a pressure difference is the only accelerating force, it is equivalent to Newton's laws of motion.

Related Topics:
Fluid - Velocity - Pressure - Dutch - Swiss - Daniel Bernoulli - Leonhard Euler - Bernoulli's equation - Viscosity - Newton's laws of motion

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One way of understanding how an airfoil develops lift relies upon the pressure differential above and below a wing. The pressure can be calculated by finding the velocities around the wing and using Bernoulli's equation. However, this explanation often uses false information, such as the incorrect assumption that the two parcels of air which separate at the leading edge of a wing must meet again at the trailing edge.

Related Topics:
Airfoil - Lift - Bernoulli's equation

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Bernoulli's principle is responsible for the venturi effect that is used in carburetors and elsewhere. In a carburetor, air is passed through a Venturi tube to increase its speed and therefore decrease its pressure. The low pressure air is routed over a tube leading to a fuel tank. The low pressure sucks the fuel into the airflow so that the combined fuel and air can be sent to the engine. The pressure reduction is proportional to the rate of air flow, so that more fuel is sucked in as the air flow increases, and the fuel/air mixture keeps the same proportion over a wide range of speeds. The pressure reduction effect can be observed by blowing over a straw; the liquid level will rise as the flow over the top of the straw increases in speed.

Related Topics:
Venturi effect - Carburetor - Venturi tube

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Another important application is predicting and preventing cavitation. As an example, a ship's propeller rotating at high speed may cause the local water (or other liquid) pressure to decrease enough for the liquid to become a gas (boil at low temperature), producing bubbles. When these collapse, pitting occurs on the face of the propeller, and noise results. The latter may be detected by means of sonar.

Related Topics:
Cavitation - Propeller - Boil - Bubble - Pitting - Sonar

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