Name: fluid head profiles in pipes and channels
Uploaded: 2025-02-13T15:43:14.000Z
Duration: 1 min 27 s
Channel: JoVE

Em um fluido que flui através de um tubo, a linha de energia representa a energia total do fluido, combinando cargas de pressão, velocidade e elevação.
Em contraste, a linha de gradiente hidráulico mostra apenas a soma das cargas de pressão e elevação, excluindo a velocidade.
Essas linhas representam visualmente a distribuição de energia e pressão em um sistema de fluxo de fluido.
A diferença entre essas linhas é a carga de velocidade; a linha de energia é sempre maior que a linha de gradiente hidráulico durante o fluxo.
Em um fluido estacionário, as linhas de gradiente hidráulico e de energia coincidem.
A pressão positiva ocorre quando a linha de gradiente hidráulico está acima do tubo; a pressão negativa acontece quando está abaixo, potencialmente causando problemas como cavitação.
Manter o gradiente hidráulico acima da elevação do tubo evita problemas como entrada de ar e falha estrutural da tubulação.
Em sistemas de sifão, a compreensão dessas linhas garante pressão adequada para sustentar o fluxo ininterrupto.
O monitoramento dessas linhas ajuda a detectar vazamentos ou bloqueios e projetar sistemas para evitar golpe de aríete ou refluxo.
Instrumentos como tubos de Pitot e piezômetros medem essas linhas, auxiliando no projeto e análise de sistemas hidráulicos na engenharia civil.

linha de energia e linha de gradiente hidráulico

Energy Line and Hydraulic Gradient Line

Com base na equação de Bernoulli, a linha de energia (EL) e a linha de grau hidráulico (HGL) fornecem representações gráficas da distribuição de energia em um sistema de fluxo de fluido. Para fluxos estáveis, incompressíveis e invíscidos, a equação de Bernoulli é expressa como:

<img alt="Equation 1" src="/files/ftp_upload/18039/18039_Equation_1.svg" style="text-align: center; height: 34px;">

Aqui, H é a altura manométrica total, p/γ​ é a altura manométrica de pressão, V^2/2g​ é a altura manométrica de velocidade e z é a altura manométrica de elevação.

A linha de energia (EL) representa a altura manométrica total disponível no fluxo. Ela está localizada acima do datum e inclui todos os três componentes de energia. Em condições ideais, ela permanece horizontal, pois a energia total não varia ao longo de uma linha de corrente. A elevação da EL pode ser medida usando um tubo de Pitot, que captura a pressão de estagnação e fornece o valor total de energia.

A linha de grau hidráulico (HGL) descreve a altura manométrica piezométrica (p/γ+ z), que exclui a altura manométrica de velocidade. Ele fica abaixo do EL por uma distância vertical, que é igual à altura de velocidade (V^2/2g​). O HGL representa variações de pressão no sistema. Em tubulações pressurizadas, ele fica acima do tubo, enquanto no fluxo de canal aberto, ele coincide com a superfície da água.

Se a velocidade do fluido ou o diâmetro do tubo mudar, a elevação do HGL se ajusta de acordo. A altura de pressão é zero na saída do tubo, fazendo o HGL coincidir com a altura de elevação. Para um fluxo estável e invíscido de um tanque, o EL e o HGL são horizontais, refletindo a altura constante e a pressão atmosférica de saída.

As aplicações práticas geralmente incorporam efeitos viscosos e perdas, que distorcem o EL e o HGL. Esses conceitos são cruciais para analisar distribuições de pressão e energia em sistemas de fluidos.

Linha de energia e linha de gradiente hidráulico

Em um fluido que flui através de um tubo, a linha de energia representa a energia total do fluido, combinando cargas de pressão, velocidade e elevação.
Em...

Education

JoVE Core

Civil Engineering

Engenharia Civil

Unit 1

Unidade 1

Fluid Dynamics

Dinâmica de Fluidos

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

fluid head profiles in pipes and channels

Fluid head profiles in pipes and channels show how pressure, speed, and height change in a flowing fluid. These profiles come from Bernoulli's equation for steady, incompressible, inviscid flow. In that equation, total head includes pressure head, velocity head, and elevation head.

The energy line (EL) shows the total head available in the flow. It sits above the datum and includes all three energy parts. Under ideal conditions, the EL stays horizontal because the total energy does not change along a streamline. A Pitot tube can be used to measure the EL by capturing stagnation pressure and giving the total energy value.

The hydraulic grade line (HGL) shows the piezometric head, which is the pressure head plus the elevation head. It does not include the velocity head. The HGL lies below the EL by a vertical distance equal to the velocity head, V²/2g. It helps show pressure changes in the system.

In a pressurized pipeline, the HGL is usually above the pipe. In open-channel flow, it matches the water surface. If fluid velocity changes or the pipe diameter changes, the HGL position changes too. At a pipe outlet, pressure head is zero, so the HGL meets the elevation head.

For steady, inviscid flow from a tank, both the EL and HGL are horizontal. This reflects constant head and atmospheric pressure at the outlet. In real systems, viscous effects and losses can bend these lines. These ideas are important for reading pressure and energy in fluid systems.

Fluid Head Profiles in Pipes and Channels

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Pressure and Speed in Bernoulli's Equation

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Pitot-Static Measurement in Bernoulli Flow

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Fluid Flow and Area Changes

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energy line and hydraulic gradient line

Fluid head profiles in pipes and channels show how pressure, speed, and height change in a flowing fluid. These profiles come from Bernoulli's equation for steady, incompressible, inviscid flow. In that equation, total head includes pressure head, velocity head, and elevation head. The energy line (EL) shows the total head available in the flow. It sits above the datum and includes all three energy parts. Under ideal conditions, the EL stays horizontal because the total energy does not change...

design example: designing water slide

Water Slide Speed and Bernoulli's Principle

Water slide speed is controlled by Bernoulli's principle and the height of the slide. Engineers use these ideas to keep the ride exciting while making sure the water stays safe for riders. As water moves downhill, gravity makes it speed up. The water at the bottom depends on the height it starts from. A taller slide gives the water more potential energy at the top. That energy changes into kinetic energy as the water descends, so the flow becomes faster. Bernoulli's principle helps describe...

key terms and concepts

Learn how the energy line and hydraulic grade line show total head, pressure changes, and velocity effects in pipes, tanks, and open channels.

Fluid Head Profiles in Pipes and Channels | 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

Fluid Head Profiles in Pipes and Channels

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