Venturi Effect

Information about Venturi Effect

For other uses, see Venturi (disambiguation).

A Venturi meter is shown in a diagram, the pressure in "1" conditions is higher than "2", and the relationship between the fluid speed in "2" and "1" respectively, is the same as for pressure.

The Venturi effect is an example of Bernoulli's principle, in the case of incompressible fluid flow through a tube or pipe with a constriction in it. The fluid velocity must increase through the constriction to satisfy the equation of continuity, while its pressure must decrease due to conservation of energy: the gain in kinetic energy is supplied by a drop in pressure or a pressure gradient force. The effect is named after Giovanni Battista Venturi, (1746–1822), an Italian physicist.

The limiting case of the Venturi effect is choked flow, in which a constriction in a pipe or channel limits the total flow rate through the channel, because the pressure cannot drop below zero in the constriction. Choked flow is used to control the delivery rate of water and other fluids through spigots and other valves.

Referring to the diagram to the right, using Bernoulli's equation in the special case of incompressible fluids (such as the approximation of a water jet), the theoretical pressure drop at the constriction would be given by (ρ/2)(v₂² - v₁²).

Experimental apparatus

This is a Venturi tube demonstration apparatus built out of PVC pipe and operated with a vacuum pump.

Venturi Tubes

The simplest apparatus, as shown in the photograph and diagram, is a tubular setup known as a Venturi tube or simply a venturi. Fluid flows through a length of pipe of varying diameter. To avoid undue drag, a venturi tube typically has an entry cone of 30 degrees and an exit cone of 5 degrees.

A venturi can also be used to mix a fluid with air. If a pump forces the fluid through a tube connected to a system consisting of a venturi to increase the water speed (the diameter decreases), a short piece of tube with a small hole in it, and last a venturi that decreases speed (so the pipe gets wider again), air will be sucked in through the small hole because of changes in pressure. At the end of the system, a mixture of fluid and air will appear.

Orifice plate

Venturi tubes are more expensive to construct than a simple orifice plate which uses the same principle as a tubular scheme, but the orifice plate causes significantly more permanent energy loss and is less accurate.

In Chronic Aortic Regurgitation, after the initial large stroke volume is released, the Venturi effect draws walls together, transiently obstructing flow causing a Pulsus Bisferiens.

Practical uses

The Venturi effect is visible in:

the capillaries of the human circulatory system, where it indicates aortic regurgitation
large cities where wind is forced between buildings.
inspirators that mix air and flammable gas in barbecues, gas stoves, Bunsen burners and Airbrushes.
water aspirators that produce a partial vacuum using the kinetic energy from the faucet water pressure
Steam siphon using the kinetic energy from the steam pressure to create a partial vacuum
atomizers that disperse perfume or spray paint (i.e. from a spray gun)
foam firefighting nozzles and extinguishers
carburetors that use the effect to suck gasoline into an engine's intake air stream.
Protein skimmers, a filtration device for saltwater aquaria.
In automated pool cleaners that use pressure-side water flow to collect sediment and debris.
The modern day barrel of the clarinet, which uses a reverse taper to speed the air down the tube, enabling better tone, response and intonation.
Compressed air operated industrial vacuum cleaners
Venturi scrubbers used to clean flue gas emissions
Injectors (or sometimes called ejectors) used to add chlorine gas in water treatment chlorination systems
Sand blasters use the effect to draw fine sand in and mix it with air
Emptying bilge water from a moving boat through a small waste gate in the hull. The air pressure inside the moving boat is greater than the water sliding by beneath.
A SCUBA diving regulator may use the effect to assist the flow of air once it starts flowing.

A simple way to demonstrate the Venturi effect is to squeeze and release a flexible hose that is normal shape: the partial vacuum produced in the constriction is sufficient to keep the hose collapsed.

Venturi tubes are also used to measure the speed of a fluid, by measuring pressure changes at different segments of the device. Placing a liquid in a U-shaped tube and connecting the ends of the tubes to both ends of a venturi is all that is needed. When the fluid flows though the venturi the pressure in the two ends of the tube will differ, forcing the liquid to the "low pressure" side. The amount of that move can be calibrated to the speed of the fluid flow.

People

Giovanni Battista Venturi, (b 1746) physicist.
Ken Venturi, (b 1931) professional golfer.
Rick Venturi, American football coach.
Robert Venturi, (b 1925) architect.

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Bernoulli's equation redirects here; see Bernoulli differential equation for an unrelated topic in ordinary differential equations.

Bernoulli's Principle
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velocity is defined as the rate of change of position. It is a vector physical quantity, both speed and direction are required to define it. In the SI (metric) system, it is measured in meters per second (m/s). The scalar absolute value (magnitude) of velocity is speed.
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conservation of energy states that the total amount of energy in any closed system remains constant but can be recreated, although it may change forms, e.g. friction turns kinetic energy into thermal energy.
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kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity.
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The pressure gradient force is the force that is usually responsible for accelerating a parcel of air from a high atmospheric pressure region to a low pressure region, resulting in wind.
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Giovanni Battista Venturi (1746 - 1822) was an Italian physicist. He was the discoverer and eponym of Venturi effect. He was also the eponym of the Venturi pump and Venturi tube.

Born in Bibbiano, he was a contemporary of Leonhard Euler and Daniel Bernoulli.
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120 - 140 million (est.)
Regions with significant populations Italy 56 million (95% population of Italy)

Brazil ^[1]
Argentina
United States ^[2]
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Physics is the science of matter^[1] and its motion^[2]^[3], as well as space and time^[4]^[5] —the science that deals with concepts such as force, energy, mass, and charge.
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Choked flow of a fluid is a fluid dynamic condition caused by the Venturi effect. When a flowing fluid at a certain pressure and temperature flows through a restriction (such as the hole in an orifice plate or a valve in a pipe) into a lower pressure environment, under the
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Water is a common chemical substance that is essential to all known forms of life.^[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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tap is a valve for controlling the release of a liquid or gas. In the British Isles and normally in the Commonwealth the word is used for any everyday type of valve, particularly the fittings that control water supply to bathtubs and sinks. In the U.S.
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An orifice plate is a device used to measure the rate of fluid flow. It uses the same principle as a Venturi nozzle, namely Bernoulli's principle which says that there is a relationship between the pressure of the fluid and the velocity of the fluid.
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In medicine, pulsus bisferiens, also bisferious pulse or biphasic pulse, is a sign where, on palpation of the pulse, a double peak per cardiac cycle can be appreciated. Bisferious means striking twice.
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capillary is used to describe any very narrow tube or channel through which a fluid can pass. See capillary action for details.

Capillaries are the smallest of a body's blood vessels, measuring 5-10 μm, which connect arterioles and venules, and are
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Circulatory System is a psychedelic rock musical ensemble formed by musician/painter Will Cullen Hart, and featuring Hannah Jones, Derek Almstead, Peter Erchick, John Fernandes, and Heather McIntosh.
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MeSH D001022 Aortic insufficiency (AI), also known as aortic regurgitation (AR), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle.
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An inspirator is a device, similar to a venturi tube and an orifice plate, which mixes a fuel gas with atmospheric air in a precise ratio to regulate burn characteristics. Only the pressure of the fuel gas is used to draw in and mix the air.
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Barbecue or barbeque ^[1] (abbreviated BBQ or Bar-B-Que or diminuted, chiefly in Australia, New Zealand and the United Kingdom to barbie, and braai
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gas stove is a cooker which uses natural gas as a fuel source.

The first gas stoves were developed already in the 1820s, but these remained isolated experiments. (James Sharp patented a gas stove in Northampton, England in 1826 and opened a gas stove factory in 1836.
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Bunsen burner is a common piece of laboratory equipment used for heating, sterilization, and combustion.

History

A common misconception is that the Bunsen burner was invented by German chemist Robert Wilhelm Bunsen and Christian Schonbein.
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An airbrush is a small, air-operated tool that sprays various media including ink and dye, but most often paint by a process of atomization. Spray guns developed from the airbrush and are still considered a type of airbrush.
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aspirator, also called an ejector or filter pump, is a device that produces vacuum by means of the Venturi effect. In an aspirator, fluid (liquid or gaseous) flows through a tube which then narrows.
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Atomization (British English: atomisation) is conversion of bulk liquid into a spray or mist (i.e. collection of drops), often by passing the liquid through a nozzle.
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carburetor (North American spelling) / carburettor (international spelling), colloquially called a carb (in North America and the United Kingdom) or carby (chiefly in Australia), is a device that blends air and fuel for an internal combustion engine.
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Gasoline or petrol is a petroleum-derived liquid mixture consisting mostly of aliphatic hydrocarbons and enhanced with aromatic hydrocarbons toluene, benzene or iso-octane to increase octane ratings, primarily used as fuel in internal combustion engines.
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A protein skimmer or foam fractionator is a device used mostly in saltwater aquaria to remove organic compounds from the water before they break down into nitrogenous waste.
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aquarium (plural aquariums or aquaria) is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Aquaria are primarily used for fishkeeping, although invertebrates, amphibians, marine mammals, and aquatic plants
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automated pool cleaner is a robotic vacuum cleaner intended to collect debris and sediment from swimming pools. Most models use a random motion pattern to ensure that the entire floor surface is eventually covered.
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clarinet is a musical instrument in the woodwind family. The name derives from adding the suffix -et meaning little to the Italian word clarino meaning a particular type of trumpet, as the first clarinets had a strident tone similar to that of a trumpet.
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