vena contracta

physics

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Last updated

July 14, 2026

Quick Summary

The vena contracta refers to the contracted part of a fluid jet that has the minimum cross-section. This phenomenon occurs when a fluid discharges from an orifice, causing the streamlines to converge and then diverge, resulting in a narrowing of the jet just outside the opening.1

In fluid mechanics, this concept is related to Bernoulli's law, which describes the relationship between pressure, velocity, and height in a moving fluid. When a fluid flows through a constriction, its velocity increases, and its pressure decreases. The vena contracta is the point where this velocity is highest and pressure is lowest within the jet.2

The coefficient of contraction is a physics term that quantifies this effect. It is defined as the ratio of the cross-sectional area of the vena contracta to the area of the discharge aperture. This coefficient helps in understanding and calculating fluid flow rates.3

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fluid mechanics
Bernoulli’s law
…cross section known as the vena contracta. They do so because the streamlines are converging on the hole inside the vessel and are obliged to continue converging for a short while outside. It was Torricelli who first suggested that, if the pressure excess inside the vessel is generated by a…
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…cross section known as the vena contracta. They do so because the streamlines are converging on the hole inside the vessel and are obliged to continue converging for a short while outside. It was Torricelli who first suggested that, if the pressure excess inside the vessel is generated by a…
Read More