Venturi effect

The Venturi effect is a pressure decrease that occurs as a fluid accelerates through a constricted passage. It follows from conservation of mass and energy in flowing fluids.

Bernoulli's principle: A relation among pressure, speed, and height in steady, incompressible, nonviscous fluid flow. It predicts the pressure drop accompanying increased speed through a constriction.
Venturi meter: A flowmeter that estimates a fluid's flow rate from the pressure difference across a constriction. It uses the effect to measure flow without a moving sensing element.
Conservation of mass: The principle that mass is neither created nor destroyed in a closed system. Steady flow through a passage applies this principle to fluid throughput.
Torricelli's law: A relation giving the ideal exit speed of liquid draining from a tank under gravity. It links speed to a pressure or height difference without a constricted passage.
Continuity equation: A conservation law requiring steady flow through a passage to carry the same mass per unit time across each section. It explains why fluid speeds up where the passage narrows.
Carburetor: A device that mixes fuel with air for an internal-combustion engine. Air accelerating through its throat lowers pressure and draws in fuel.
Conservation of energy: The principle that energy changes form but is not created or destroyed. The pressure-speed tradeoff is an energy balance in the ideal-flow model.
Coandă effect: The tendency of a fluid jet to remain attached to a nearby curved surface. It concerns jet attachment, not the pressure-speed relation in a throat.
Static pressure: The pressure exerted by a fluid at rest relative to its local motion. The Venturi effect concerns a decrease in this pressure as flow accelerates.
Aspirator: A device that uses a fast-moving fluid jet to draw in and mix with another fluid. Its suction can arise from low pressure near the accelerating jet.

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