Name: bernoulli's principle in fluid devices
Uploaded: 2023-05-16T08:18:41.000Z
Duration: 1 min 17 s
Channel: JoVE

Il principio di Bernoulli ha diverse applicazioni pratiche, come i bruciatori Bunsen, le bottiglie di profumo e gli ugelli per manichette antincendio.
Un tubo Venturi è una di queste applicazioni, utilizzato per misurare la velocità di un fluido che scorre in un tubo.
È costituito da una parte convergente, la gola, e da una parte divergente.
Due sottili tubi verticali sono collegati a un tubo Venturi, uno prima della parte convergente e uno nella regione della gola.
Il suo funzionamento si basa sull'equazione di continuità e sul principio di Bernoulli.
Secondo l'equazione di continuità, se l'area della sezione trasversale del tubo diminuisce, la velocità del flusso deve aumentare.
Secondo il principio di Bernoulli, l'aumento della velocità del flusso è accompagnato da una diminuzione della pressione.
Quindi, la pressione vicino all'ingresso è alta e la pressione al centro della regione della gola è bassa. La differenza di altezza del livello del fluido nei tubi verticali è la misura della differenza di pressione.
Se le aree della sezione trasversale sono note, si possono risolvere queste equazioni per ottenere la velocità del fluido che scorre attraverso il tubo.

<ol>
	<li>OpenStax. (2019). Fisica universitaria Vol. 1. [Versione web]. Estratto dalla sezione 14.6, pp-719-720. <a href="https://openstax.org/books/university-physics-volume-1/pages/14-6-bernoullis-equation">https://openstax.org/books/university-physics-volume-1/pages/14-6-bernoullis-equation</a></li>
</ol>

principio di bernoulli: applicazioni

Ci sono molti dispositivi e situazioni in cui un fluido fluisce a una altezza costante e può quindi essere analizzato utilizzando il principio di Bernoulli. Questi dispositivi includono, ma non sono limitati a, dispositivi di traino e dispositivi di misurazione del flusso fluidico.

I dispositivi di traino utilizzano una velocità elevata del fluido per creare basse pressioni e, quindi, trainano un fluido nell'altro. Di seguito sono riportati alcuni esempi di questi dispositivi:

<ol>
	<li>Una lampada di Bunsen utilizza una bocchetta del gas regolabile per trainare l'aria per una corretta combustione.</li>
	<li>Un atomizzatore utilizza una pompa a compressione per creare un getto d'aria che traina gocce di profumo.</li>
	<li>Pistole a spruzzo di vernice e carburatori utilizzano tecniche molto simili per muovere i rispettivi liquidi.</li>
	<li>Un aspiratore comune utilizza un flusso ad alta velocità d'acqua per creare una regione a pressione inferiore. Gli aspiratori possono essere utilizzati come pompe di aspirazione in situazioni dentali e chirurgiche, per svuotare un seminterrato allagato, o per ridurre la pressione in un recipiente.</li>
	<li>Il camino di un scaldabagno è progettato per trainare l'aria nel tubo che passa attraverso il soffitto.</li>
</ol>

Alcuni dispositivi utilizzano il principio di Bernoulli per la misurazione della velocità del fluido. Esempi di questi dispositivi includono i tubi di Prandtl, anche conosciuti come tubi di Pitot, i tubi di Venturi, e un manometro collegato a due tubi che sono vicini tra loro e abbastanza piccoli da non disturbare il flusso.

Principio di Bernoulli: applicazioni

Esistono molti dispositivi e situazioni in cui il fluido scorre ad un'altezza costante e quindi può essere analizzato utilizzando il principio di Bernoulli. Questi dispositivi ...

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Education

Didattica

JoVE Core

Physics

Fisica

Unit 1

Unità 1

Fluid Mechanics

Meccanica dei Fluidi

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Bernoulli's Principle: Applications

bernoulli's principle in fluid devices

Bernoulli's principle helps explain how many fluid devices work when the fluid moves at a constant height. It is useful for devices that use fast flow to create low pressure and for devices that measure fluid speed.

Some devices use this pressure change to pull one fluid into another. These are called entrainment devices. A Bunsen burner uses an adjustable gas nozzle to entrain air for proper combustion. An atomizer uses a squeeze bulb to make a jet of air that pulls perfume drops into the flow. Paint sprayers and carburetors work in a very similar way to move their liquids.

Other examples include a common aspirator, which uses a high-speed stream of water to create a lower-pressure region. Aspirators can act as suction pumps in dental and surgical settings. They can also help drain a flooded basement or reduce the pressure in a vessel. A water heater chimney is also designed to entrain air into the pipe leading through the ceiling.

Bernoulli's principle is also used to measure fluid speed. Prandtl tubes, also called pitot tubes, Venturi tubes, and a manometer connected to two close tubes can all be used for this purpose. The tubes must be close together and small enough not to disturb the flow.

Bernoulli's Principle in Fluid Devices

characteristics of fluids

Fluid Behavior Under Force

Fluid behavior under force differs from the behavior of solids. When a force acts parallel to the top surface of a solid, the solid resists it because of internal friction between its layers. This is called shearing resistance. If the force is removed, the shearing forces help the solid return to its original shape. Other deformation forces can also change the shape of a solid for a short time, as long as the force stays below a threshold magnitude. Solids usually keep their shape, which makes...

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density

Density, Floating, and Specific Gravity

Density helps explain why objects sink or float in a fluid. It is also useful for identifying a substance and for learning about its phase and substructure. The SI unit of density is kg/m3, and the cgs unit is g/cm3. Liquids and solids usually have densities that are roughly comparable. That matches the fact that their atoms are in close contact. Gases have much lower densities than liquids and solids because their atoms are separated by large amounts of empty space. Density does not always...

pressure of fluids

Fluid Pressure in Everyday Life

Fluid pressure appears in many everyday situations, including blood pressure and weather systems. The same force can have a very different effect depending on the area it acts on. A force spread over 1 mm² creates 100 times more pressure than the same force spread over 1 cm². That is why a sharp needle can pierce skin with a small force, while the same force from a finger usually does not. Pressure is especially important when studying fluids. A fluid does not offer much resistance to a force...

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Atmospheric Pressure and Altitude

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pascal's law

Pascal’s Principle in Static Fluids

Pascal’s principle explains how pressure changes move through a fluid that is not flowing. A fluid at rest is in static equilibrium. If the fluid is water, it is in hydrostatic equilibrium. In this state, the net force on any part of the fluid must be zero, or the fluid will begin to flow. Blaise Pascal described this idea in 1653 in Treatise on the Equilibrium of Liquids. He showed that when pressure changes in an enclosed fluid, that change is transmitted without loss through the fluid and...

application of pascal's law

Hydraulic Force Transfer with Pascal's Law

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archimedes' principle

Buoyant Force from Fluid Pressure

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accelerating fluids

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excess pressure inside a drop and a bubble

excess-pressure-inside-a-drop-and-a-bubble

Surface Tension in Drops and Bubbles

Surface tension sets the pressure difference in small drops and bubbles. For a tiny liquid drop, gravity can be neglected, so the drop is treated as spherical. It can also be viewed as two equal hemispherical drops joined together by surface tension. The forces on the drop come from three sources. The liquid inside pushes outward, the air outside pushes inward, and surface tension acts along the diameter between the two hemispheres. Since surface tension is force per unit length, it creates a...

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buoyancy

Buoyant Force in Sinking and Floating

Buoyant force explains why objects float, sink, or stay suspended in a fluid. A fluid can be a liquid or a gas, and every object placed in it experiences this upward force. A metal ball sinks, while a rubber ball floats. A submarine also changes its buoyancy to move up or down. The force comes from pressure changes in the fluid. Fluid pressure increases with depth because the weight of the fluid above also increases. That means the bottom of an object feels more pressure than the top. This...

contact angle

Wetting and Surface Curvature

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rise of liquid in a capillary tube

Capillary Action in Thin Tubes

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laminar and turbulent flow

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bernoulli's equation

Fluid Pressure and Speed in Motion

Bernoulli's equation connects fluid pressure with fluid speed. It helps explain why moving fluids can create pressure changes in everyday situations. One example is when two trains pass each other quickly and seem to pull inward. The same effect can happen when two cars pass each other at high speed. As the air between the trains or cars speeds up, its pressure drops. The air on the outside stays at atmospheric pressure. That pressure difference creates a net inward force on the vehicles.

bernoulli's principle

Fluid Pressure and Speed Changes

Bernoulli's equation links fluid pressure and fluid speed in a static, incompressible fluid. For horizontal flow, where gravitational energy density stays constant, the equation is especially useful. In that setting, the result is known as Bernoulli's principle. Bernoulli's principle says that fluid pressure drops when speed increases, and pressure rises when speed decreases. This pressure-speed relationship helps explain how moving fluids behave in simple flow situations. It also provides a...

bernoulli's principle: applications

Bernoulli's principle helps explain how many fluid devices work when the fluid moves at a constant height. It is useful for devices that use fast flow to create low pressure and for devices that measure fluid speed. Some devices use this pressure change to pull one fluid into another. These are called entrainment devices. A Bunsen burner uses an adjustable gas nozzle to entrain air for proper combustion. An atomizer uses a squeeze bulb to make a jet of air that pulls perfume drops into the...

energy conservation and bernoulli's equation

energy-conservation-and-bernoulli-s-equation

Bernoulli’s Equation in Streamlined Flow

Bernoulli’s equation describes energy in a moving fluid. It comes from the conservation of energy principle, or the work-energy theorem, applied to an incompressible, inviscid fluid in laminar, steady, irrotational flow. The equation says that pressure energy, potential energy, and kinetic energy per unit volume stay constant along a streamline. Each term has the units of energy per unit volume. The kinetic energy per unit volume is called kinetic energy density, and the potential energy per...

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viscosity

Viscosity and How Fluids Flow

Viscosity describes how easily a fluid flows. Water moves quickly, while honey and maple syrup flow slowly and stick to a surface. That difference comes from fluid friction between liquid layers and between a fluid and the material around it. In this example, water has a lower viscosity than honey and maple syrup. Viscosity is measured in newton-second per meter squared (N·s/m2) or pascal-second (Pa·s). It also changes with temperature and can differ from one fluid to another by several orders...

poiseuille's law and reynolds number

Fluid Resistance, Viscosity, and Flow Regime

Fluid resistance, viscosity, and flow regime shape how liquid moves through a horizontal tube. Fluid flows from high pressure to low pressure. The flow rate, Q, is the ratio of the pressure difference to the resistance in the tube. A larger pressure difference gives a higher flow rate. Poiseuille's law describes laminar flow of an incompressible fluid in a tube. In this relation, the factors that affect flow rate except pressure are grouped into resistance. Resistance depends on the tube size...

stokes' law

Terminal Velocity in a Viscous Fluid

Viscous forces act like friction in a liquid. They resist the relative motion of molecules and pull back on a solid body moving through the fluid. The size of this force depends on the body’s shape and size, its speed, and the liquid’s viscosity, density, and temperature. For a spherical solid object, the force in a fluid is described by Stokes’ law. This law applies only at low Reynolds number, when the flow is laminar and not turbulent. Experiments show that the force is proportional to the...

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key terms and concepts

See how Bernoulli's principle explains entrainment devices and fluid speed tools like Bunsen burners, aspirators, pitot tubes, and Venturi tubes.

Bernoulli's Principle in Fluid Devices | JoVE K12

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Bernoulli's Principle in Fluid Devices

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