Name: liquid speed from reservoir outlets
Uploaded: 2026-01-30T03:08:28.000Z
Duration: 1 min 14 s
Channel: JoVE

I getti liberi dimostrano il comportamento del fluido descritto dall'equazione di Bernoulli, poiché il fluido esce da un ugello e fluisce liberamente nell'aria.
La velocità del flusso all'ugello è determinata dall'altezza della colonna di fluido sopra di esso, che converte l'energia potenziale in energia cinetica.
La pressione di uscita del getto corrisponde alla pressione atmosferica e la velocità aumenta man mano che il fluido scorre da un grande serbatoio.
A causa dell'inerzia del fluido, il getto si restringe appena fuori dall'ugello, formando l'area della sezione trasversale più piccola. Questo fenomeno è noto come vena contratta.
Il rapporto tra l'area del getto alla vena contratta e l'area dell'ugello fornisce il coefficiente di contrazione.
Varie forme di ugelli, come i design a lama di coltello, ben arrotondati, a spigolo vivo e rientranti, influiscono sul modello di flusso e sul coefficiente di contrazione.
Nella progettazione di sistemi come sfioratori e sbarramenti, l'effetto vena contracta viene considerato per una misurazione accurata del flusso.
I getti liberi sono fondamentali nelle applicazioni di ingegneria civile per controllare il flusso dei fluidi e ridurre al minimo l'impatto strutturale.

getto libero

I getti liberi descrivono il flusso di liquido che fuoriesce da un serbatoio, attraverso un'apertura nell'atmosfera senza resistenza. La velocità (V) del getto di liquido è calcolata utilizzando il principio di Bernoulli ed espressa come:

<img alt="Equation 1" src="/files/ftp_upload/18037/18037_Equation_1.svg" style="text-align: center; height: 15px;">

Dove h è l'altezza del liquido sopra l'apertura. Questa relazione presuppone che la pressione atmosferica sia applicata sulla superficie del serbatoio e all'uscita del getto. L'altezza della colonna di fluido, regola la velocità del fluido all'ugello in un serbatoio, dove l'energia potenziale del fluido, si converte in energia cinetica durante il flusso.

Il fenomeno della vena contracta, si verifica quando il liquido esce attraverso un orifizio con bordi affilati, facendo sì che il diametro del getto d_j, sia inferiore al diametro dell'ugello d_o. Ciò si verifica perché le linee di flusso del fluido non possono seguire i bordi netti, creando una regione di flusso contratta. Il coefficiente di contrazione, è il rapporto tra l'area della sezione trasversale del getto nella vena contracta e l'area della sezione trasversale dell'ugello, e quantifica il grado di contrazione del getto. Questo parametro è influenzato dalla geometria dell'ugello, con vari design, come ugelli a lama, a lama affilata, ben arrotondati e rientranti che producono distinti schemi di flusso e caratteristiche di contrazione. Per un ugello ben arrotondato, C_c = 1,0, mentre gli orifizi affilati o a lama riducono C_c a circa 0,61. Gli ugelli rientranti presentano valori ancora più bassi.

Queste caratteristiche di flusso ed effetti di contrazione, sono fondamentali nelle applicazioni ingegneristiche che coinvolgono lo scarico di liquidi, dai serbatoi agli ugelli industriali.

Getto Libero

I getti liberi dimostrano il comportamento del fluido descritto dall'equazione di Bernoulli, poiché il fluido esce da un ugello e fluisce liberamente nell'aria.
La velocità del flusso ...

Education

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JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Fluid Dynamics

Dinamica dei fluidi

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

Free Jet

liquid speed from reservoir outlets

Free jets show how liquid moves after leaving a reservoir through an opening and flowing into the air without resistance. The jet speed is found with Bernoulli’s principle, and it depends on the height of liquid above the opening. This relationship assumes atmospheric pressure at both the reservoir surface and the jet exit.

The liquid column’s height controls the speed at the nozzle because the fluid’s potential energy changes into kinetic energy during flow. As the liquid leaves the reservoir, its motion reflects this energy conversion. This is why a deeper liquid level can produce a faster jet.

A sharp-edged orifice can also cause vena contracta, which is the narrowed region where the jet becomes smaller than the nozzle opening. This happens because the streamlines cannot follow the abrupt edge smoothly. The contraction coefficient measures this narrowing by comparing the jet area at vena contracta with the nozzle area.

Nozzle shape changes the flow pattern and the amount of contraction. Knife-edge, sharp-edge, well-rounded, and re-entrant nozzles each produce different results. For a well-rounded nozzle, the contraction coefficient is 1.0, while sharp or knife-edged openings reduce it to about 0.61, and re-entrant nozzles produce even lower values. These effects matter in engineering systems that discharge liquid from reservoirs and industrial nozzles.

Liquid Speed from Reservoir Outlets

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free jet

Free jets show how liquid moves after leaving a reservoir through an opening and flowing into the air without resistance. The jet speed is found with Bernoulli’s principle, and it depends on the height of liquid above the opening. This relationship assumes atmospheric pressure at both the reservoir surface and the jet exit. The liquid column’s height controls the speed at the nozzle because the fluid’s potential energy changes into kinetic energy during flow. As the liquid leaves the...

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key terms and concepts

Learn how liquid speed from a reservoir depends on height, Bernoulli’s principle, and nozzle shape, including vena contracta and contraction coefficient.

Liquid Speed from Reservoir Outlets | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Liquid Speed from Reservoir Outlets

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