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Venturi effect
 
 
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The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. The fluid velocity
Velocity

In physics, velocity is defined as the Derivative of Position vector. It is a vector physical quantity; both speed and direction are required to define it....
 must increase through the constriction to satisfy the equation of continuity
Derivation of the Navier–Stokes equations

The intent of this article is to highlight the important points of the derivation of the Navier?Stokes equations as well as the application and formulation for different families of fluids....
, while its pressure must decrease due to conservation of energy
Conservation of energy

The law of conservation of energy states that the total amount of energy in an isolated system remains constant. A consequence of this law is that energy cannot be created or destroyed....
: the gain in kinetic energy
Kinetic energy

The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the mechanical work needed to accelerate a body of a given mass from rest to its current velocity....
 is balanced by a drop in pressure or a pressure gradient force
Pressure gradient force

The pressure gradient force is not actually a 'force' but the acceleration of air due to pressure difference . It 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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Venturifixed2
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. The fluid velocity
Velocity

In physics, velocity is defined as the Derivative of Position vector. It is a vector physical quantity; both speed and direction are required to define it....
 must increase through the constriction to satisfy the equation of continuity
Derivation of the Navier–Stokes equations

The intent of this article is to highlight the important points of the derivation of the Navier?Stokes equations as well as the application and formulation for different families of fluids....
, while its pressure must decrease due to conservation of energy
Conservation of energy

The law of conservation of energy states that the total amount of energy in an isolated system remains constant. A consequence of this law is that energy cannot be created or destroyed....
: the gain in kinetic energy
Kinetic energy

The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the mechanical work needed to accelerate a body of a given mass from rest to its current velocity....
 is balanced by a drop in pressure or a pressure gradient force
Pressure gradient force

The pressure gradient force is not actually a 'force' but the acceleration of air due to pressure difference . It is usually responsible for accelerating a parcel of air from a high atmospheric pressure region to a low pressure region, resulting in wind....
. An equation for the drop in pressure due to venturi effect may be derived from a combination of Bernoulli's principle
Bernoulli's principle

In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy....
 and the equation of continuity.

The limiting case of the Venturi effect is when a fluid reaches the state of choked flow
Choked flow

Choked flow of a fluid is a Fluid dynamics condition caused by the Venturi effect. When a flowing fluid at a certain pressure and temperature flows through a restriction into a lower pressure environment, under the conservation of mass the fluid velocity must increase for initially subsonic upstream conditions as it flows through the smaller...
, where the fluid velocity approaches the local speed of sound. In choked flow the mass flow rate will not increase with a further decrease in the downstream pressure environment.

However, mass flow rate for a compressible fluid can increase with increased upstream pressure, which will increase the density of the fluid through the constriction (though the velocity will remain constant). This is the principle of operation of a convergent-divergent nozzle
De Laval nozzle

A de Laval nozzle is a tube that is pinched in the middle, making an hourglass-shape. It is used as a means of accelerating the flow of a gas passing through it to a supersonic speed....
.

Referring to the diagram to the right, using Bernoulli's equation in the special case of incompressible flows (such as the flow of water or low speed flow of gas), the theoretical pressure drop at the constriction would be given by .

The Venturi effect is named after Giovanni Battista Venturi
Giovanni Battista Venturi

Giovanni Battista Venturi was an Italian people physicist. He was the discoverer and eponym of Venturi effect. He was also the eponym of the Aspirator and Venturi effect tube....
, (1746–1822), an Italian
Italian people

The Italian people are a Southern European ethnic group located primarily in Italy and, by virtue of a wide-ranging Italian diaspora, throughout Western Europe, the Americas and Australia....
 physicist
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
.

Experimental apparatus

Green Hope High School (physics Laboratory Venturi Tube) 2006
*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 be used to measure the volumetric flow rate
Volumetric flow rate

The volumetric flow rate in fluid dynamics and hydrometry, is the volume of fluid which passes through a given surface per unit time Volumetric flow rate should not be confused with volumetric flux, as defined by Darcy's law and represented by the symbol q, with units of m3/, that is, m s-1....
.


Since


Then


A venturi can also be used to mix a liquid with a gas. If a pump forces the liquid 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), the gas will be sucked in through the small hole because of changes in pressure. At the end of the system, a mixture of liquid and gas will appear. See aspirator
Aspirator

An aspirator, also called an eductor-jet pump or filter pump, is a device that produces vacuum by means of the Venturi effect. In an aspirator, fluid flows through a tube which then narrows....
 and pressure head
Pressure head

Pressure head is a term used in fluid mechanics to represent the internal energy of a fluid due to the pressure exerted on its container. It may also be called static pressure head or simply static head ....
 for a discussion of this type of siphon
Siphon

A siphon is a continuous tube that allows liquid to drain from a reservoir through an intermediate point that is higher, or lower, than the reservoir, the flow being driven only by the difference in hydrostatic pressure without any need for pumping....
.


  • Orifice plate
Venturi tubes are more expensive to construct than a simple orifice plate
Orifice plate

An orifice plate is a device used to measure the rate of fluid flow. It uses the same principle as a Venturi effect nozzle, namely Bernoulli's principle which says that there is a relationship between the pressure of the fluid and the velocity of the fluid....
 which uses the same principle as a tubular scheme, but the orifice plate causes significantly more permanent energy loss.


Aortic insufficiency
Aortic insufficiency

Aortic insufficiency , also known as aortic regurgitation , 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....
 is a chronic heart condition
Heart condition

Heart conditions can be either Acute or chronic , and either congenital or acquired.Heart Condition is a 1990 drama, comedy, action film with Denzel Washington and Bob Hoskins....
 that occurs when the aortic valve
Aortic valve

The aortic valve is one of the heart valve of the heart. It lies between the left ventricle and the aorta....
's initial large stroke volume is released and the Venturi effect draws the walls together, which obstructs blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
 flow, which leads to a Pulsus Bisferiens
Pulsus bisferiens

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....
.

Practical uses

The Venturi effect may be observed or used in the following:
  • The capillaries of the human circulatory system
    Circulatory system

    The circulatory system is an organ that moves nutrients, gases, and wastes to and from cells to help fight diseases and help stabilize body temperature and pH to maintain homeostasis....
    , where it indicates aortic regurgitation
    Aortic insufficiency

    Aortic insufficiency , also known as aortic regurgitation , 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....
  • Large cities where wind is forced between buildings
  • Inspirators
    Inspirator

    An inspirator is a device, similar to a Venturi effect and an orifice plate, which mixes a fuel gas with atmospheric air in a precise ratio to regulate burn characteristics....
     that mix air and flammable gas in grill
    Grill (cooking)

    There are multiple varieties of grills, with most falling into one of two categories: gas-fueled and charcoal. There is a great debate over the merits of charcoal or gas for use as the cooking method between grillers....
    s, gas stove
    Gas stove

    In cooking, a gas stove is a cooker which uses natural gas as a fuel source.The first gas stoves were developed as early as the 1820s, but these remained isolated experiments....
    s, Bunsen burner
    Bunsen burner

    A Bunsen burner is a common piece of laboratory equipment that produces a single open gas flame, which is used for heating, sterilization, and combustion....
    s and airbrush
    Airbrush

    An airbrush is a small, Pneumatics tool that sprays various media including ink and dye, but most often paint by a process of nebulization. Spray guns developed from the airbrush and are still considered a type of airbrush....
    es
  • Water aspirators that produce a partial vacuum using the kinetic energy from the faucet water pressure
  • Steam siphons 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
  • Carburetor
    Carburetor

    A carburetor or carburettor , is a device that blends Earth's atmosphere and fuel for an internal combustion engine. It was invented by Karl Benz before 1885 and patented in 1886....
    s that use the effect to suck gasoline
    Gasoline

    File:GasCan.jpgGasoline or petrol is a petroleum-derived liquid mixture, primarily used as fuel in internal combustion engines.It consists mostly of aliphatic hydrocarbons, enhanced with iso-octane or the aromatic hydrocarbons toluene and benzene to increase its octane rating....
     into an engine's intake air stream
  • Protein skimmer
    Protein skimmer

    A protein skimmer or foam fractionator is a device used mostly in Marine aquarium to remove organic compounds from the water before they break down into nitrogenous waste....
    s (filtration devices for saltwater aquaria
    Aquarium

    An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. fishkeeping use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants....
    )
  • In automated pool cleaner
    Automated pool cleaner

    An Automated Pool Cleaner is an vacuum cleaner intended to collect debris and sediment from swimming pools with minimum human intervention. Pools using such a cleaner on a routine basis are not only visually cleaner but also using less chemicals which means lower operating costs....
    s that use pressure-side water flow to collect sediment and debris
  • The barrel of the modern-day clarinet
    Clarinet

    The 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....
    , 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 scrubber
    Venturi scrubber

    A venturi scrubber is designed to effectively use the energy from the inlet gas stream to atomize the liquid being used to scrub the gas stream....
    s used to clean flue gas
    Flue gas

    Flue gas is gas that exits to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator....
     emissions
  • Injectors (also called ejectors) used to add chlorine gas to water treatment chlorination systems
  • Sand blasters used to draw fine sand in and mix it with air
  • Emptying bilge
    Bilge

    The bilge is the lowest compartment on a ship where the two sides meet. The word was first coined in 1523.The word is sometimes also used to describe the water that collects in this compartment....
     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
    Diving regulator

    A diving regulator is a pressure regulator used in a scuba set that supplies the diver with breathing gas at ambient pressure from one or more diving cylinders....
     to assist the flow of air once it starts flowing
  • Modern vaporizer
    Vaporizer

    A vaporizer is a device used to sublimate the active ingredients of plant material, commonly cannabis , tobacco, or any of many other therapeutic or medicinal herbs or blends ....
    s to optimize efficiency
  • In Venturi mask
    Venturi mask

    The venturi mask, also known as an air-entrainment mask, is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy....
    s used in medical oxygen therapy
    Oxygen therapy

    Oxygen therapy is the administration of oxygen as a therapeutic modality. Oxygen therapy benefits the patient by increasing the supply of oxygen to the lungs and thereby increasing the availability of oxygen to the body tissues....
  • In recoilless rifle
    Recoilless rifle

    A recoilless gun or recoilless rifle is a lightweight form of weapon that allows the firing of a heavier projectile than would be practical with a recoiling weapon....
    s to decrease the recoil of firing
  • Ventilators


A simple way to demonstrate the Venturi effect is to squeeze and release a flexible hose in which fluid is flowing: 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.

See also


  • Bernoulli's principle
    Bernoulli's principle

    In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy....
  • Bunsen burner
    Bunsen burner

    A Bunsen burner is a common piece of laboratory equipment that produces a single open gas flame, which is used for heating, sterilization, and combustion....
  • Choked flow
    Choked flow

    Choked flow of a fluid is a Fluid dynamics condition caused by the Venturi effect. When a flowing fluid at a certain pressure and temperature flows through a restriction into a lower pressure environment, under the conservation of mass the fluid velocity must increase for initially subsonic upstream conditions as it flows through the smaller...
  • Orifice plate
    Orifice plate

    An orifice plate is a device used to measure the rate of fluid flow. It uses the same principle as a Venturi effect nozzle, namely Bernoulli's principle which says that there is a relationship between the pressure of the fluid and the velocity of the fluid....
  • Pitot tube
    Pitot tube

    A Pitot tube is a pressure measurement instrument used to measure fluid flow velocity. The Pitot tube was invented by France engineer Henri Pitot in the early 1700s, and was modified to its modern form in the mid 1800s by French scientist Henry Darcy....
  • Venturi injector