Venturi effect
The drop in static pressure observed when a fluid flows through a constricted section of pipe.
Definition
When a fluid flows through a pipe that narrows and then widens, the continuity equation forces the velocity up in the narrow section: A₁v₁ = A₂v₂. Bernoulli's principle then says that the static pressure must drop there to conserve energy: p + ½ρv² = const. The combined result — faster flow, lower pressure at the throat — is the Venturi effect, first measured by Giovanni Battista Venturi in 1797.
The effect is used in flow meters (the Venturi meter directly reads flow rate from the pressure drop), in carburetors (the throat draws in fuel), in aspirators, in Bunsen burners, and in the narrowed throat of a jet engine's turbine stage.
History
Discovered and quantified by Giovanni Battista Venturi in his 1797 memoir on the lateral communication of motion in fluids.