User:Milton Beychok/Sandbox
A Venturi tube (or simply a venturi) is a section of piping consisting of an inlet converging conical section leading to a small diameter cylindrical section called the throat, followed by a diverging conical section leading to a cylindrical exit (see the adjacent drawing).
The volumetric flow rate, Q (m3/s), of a fluid flowing through the venturi at any given point is the product of the cross-sectional area, A (m2) at that point multiplied by the fluid's linear velocity, v (m/s), at that point. Since the volumetric flow rate is the same at any point within the venturi, the linear velocity of the fluid traveling through the smaller diameter throat of the venturi must increase which results in a decrease of pressure due to the conservation of energy.
The gain in kinetic energy resulting from the increased linear velocity in the throat is offset (i.e., balanced) by the decrease of pressure in the throat. The reduction in pressure which occurs when the fluid flows through the throat is called the Venturi effect and is named after the Italian physicist Giovanni Battista Venturi (1746 - 1822) who first observed the effect.
Thus, referring to the adjacent drawing, the pressure p2 and the cross-sectional area A2 in the throat are smaller than the pressure p1 and the cross-sectional area A1 in the cylindrical inlet section. The linear velocity v2 in the throat is higher than the linear velocity v1 in the inlet section.