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

Os jatos livres demonstram o comportamento do fluido descrito pela equação de Bernoulli, à medida que o fluido sai de um bico e flui livremente para o ar.
A velocidade do fluxo no bico é determinada pela altura da coluna de fluido acima dele, que converte energia potencial em energia cinética.
A pressão de saída do jato corresponde à pressão atmosférica e a velocidade aumenta à medida que o fluido flui de um grande reservatório.
Devido à inércia do fluido, o jato se estreita fora do bico, formando a menor área da seção transversal. Esse fenômeno é conhecido como veia contraída.
A razão entre a área do jato na veia contracta e a área do bico fornece o coeficiente de contração.
Vários formatos de bicos, como designs de ponta de faca, bem arredondados, afiados e reentrantes, afetam o padrão de fluxo e o coeficiente de contração.
Ao projetar sistemas como vertedouros e açudes, o efeito veia contracta é considerado para uma medição precisa da vazão.
Os jatos livres são cruciais em aplicações de engenharia civil para controlar o fluxo de fluidos e minimizar o impacto estrutural.

jato livre

Jatos livres descrevem o fluxo de líquido saindo de um reservatório por meio de uma abertura para a atmosfera sem resistência. A velocidade (V) do jato de líquido é derivada usando o princípio de Bernoulli e expressa como:

<img alt="Equation 1" src="/files/ftp_upload/18037/18037_Equation_1.svg" style="text-align: center; height: 15px;">

Onde h é a altura do líquido acima da abertura. Essa relação assume pressão atmosférica na superfície do reservatório e na saída do jato. A altura da coluna de fluido governa a velocidade do fluido no bocal em um reservatório, onde a energia potencial do fluido se converte em energia cinética durante o fluxo.

O fenômeno da vena contracta ocorre quando o líquido sai por meio de um orifício de borda afiada, fazendo com que o diâmetro do jato d_j seja menor do que o diâmetro d_o bocal. Isso ocorre porque as linhas de fluxo do fluido não podem seguir as bordas abruptas, criando uma região de fluxo contraída. O coeficiente de contração é a razão entre a área da seção transversal do jato na vena contracta e a área da seção transversal do bocal, quantificando o grau de contração do jato. Este parâmetro é influenciado pela geometria do bico, com vários designs, como bicos de lâmina afiada, de lâmina afiada, bem arredondados e reentrantes, produzindo padrões de fluxo e características de contração distintos. Para um bico bem arredondado, C_c = 1,0, enquanto orifícios afiados ou de lâmina afiada reduzem C_c para aproximadamente 0,61. Bicos reentrantes exibem valores ainda mais baixos.

Essas características de fluxo e efeitos de contração são essenciais em aplicações de engenharia envolvendo descarga de líquidos, de reservatórios a bicos industriais.

Jato Livre

Os jatos livres demonstram o comportamento do fluido descrito pela equação de Bernoulli, à medida que o fluido sai de um bico e flui livremente para o ar.
A velocidade do fluxo ...

Education

JoVE Core

Civil Engineering

Engenharia Civil

Unit 1

Unidade 1

Fluid Dynamics

Dinâmica de Fluidos

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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...

continuity equation

Fluid Flow and Area Changes

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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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