Venturi tube (redirected from Venturi effect)

venturi tube

Short pipe with a constricted inner surface, used to measure fluid flows and as a pump. The effects of constricted channels on fluid flow were first investigated by Giovanni Battista Venturi (1746–1822), but it was Clemens Herschel (1842–1930) who devised the instrument in 1888. Fluid passing through the tube speeds up as it enters the tube's narrow throat, and the pressure drops. There are countless applications for the principle, including the carburetor, in which air flows through a venturi channel at whose throat gasoline vapour enters through an opening, drawn in by the low pressure. The pressure differential can also be used to measure fluid flow (see flow meter).

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Venturi tube

A device that consists of a gradually decreasing nozzle through which the fluid in a pipe is accelerated, followed by a gradually increasing diffuser section that allows the fluid to nearly regain its original pressure head (see illustration). It can be used to measure the flow rate in the pipe, or it can be used to pump a secondary fluid by aspirating it at the nozzle exit. The ability of the venturi tube to regain much of the original pressure head makes it especially useful in measuring the flow rate in systems which have a low pressure differential or pressure head that drives the fluid through the pipe or where the cost of pumping the fluid is an important factor. Conserving the pressure head decreases the amount of energy required to pump the fluid through the pipe.

Proportions of a Herschel-type venturi tube for standard fluid-flow measurement

A gradual expansion of flow downstream of a nozzle eliminates flow separation, allowing recovery of most of the original pressure head. In the case where the main flow separates from the wall, a large percentage of the fluid energy is lost in the eddies caused by the separation.

The flow through the device obeys Bernoulli's equation, and the formula for calculating the flow is similar to the equation for orifices. The venturi meter belongs to the class of differential pressure-sensing devices that are used to indicate flow. See Bernoulli's theorem

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Venturi tube

A device that consists of a gradually decreasing nozzle through which the fluid in a pipe is accelerated, followed by a gradually increasing diffuser section that allows the fluid to nearly regain its original pressure head (see illustration). It can be used to measure the flow rate in the pipe, or it can be used to pump a secondary fluid by aspirating it at the nozzle exit. The ability of the venturi tube to regain much of the original pressure head makes it especially useful in measuring the flow rate in systems which have a low pressure differential or pressure head that drives the fluid through the pipe or where the cost of pumping the fluid is an important factor. Conserving the pressure head decreases the amount of energy required to pump the fluid through the pipe.

A gradual expansion of flow downstream of a nozzle eliminates flow separation, allowing recovery of most of the original pressure head. In the case where the main flow separates from the wall, a large percentage of the fluid energy is lost in the eddies caused by the separation.

The flow through the device obeys Bernoulli's equation, and the formula for calculating the flow is similar to the equation for orifices. The venturi meter belongs to the class of differential pressure-sensing devices that are used to indicate flow. See Flow measurement, Metering orifice