Venturi effect

The upstream static pressure (1) is higher than in the constriction (2), and the fluid speed at "1" is lower than at "2", because the cross-sectional area at "1" is greater than at "2".

A flow of air through a Venturi meter, showing the columns connected in a manometer and partially filled with water. The meter is "read" as a differential pressure head in cm or inches of water.

Idealized flow in a Venturi tube

The Venturi effect is the reduction in fluid pressure that results when a moving fluid speeds up as it is funneled from one section of a pipe to another, smaller section. As the fluid flows into a smaller area, the fluid's velocity increases, while the static pressure decreases. The Venturi effect is an example of Bernoulli's principle.

The Venturi effect is named after its discoverer, the Italian Physicist Giovanni Battista Venturi, and was first published in 1797.

The effect has various applications in engineering, architecture, and everyday objects such as atomizer nozzles and wine aerators. The reduction in pressure inside the constriction can be used both for measuring the fluid flow and for moving other fluids (e.g. in a vacuum ejector).