Name: how temperature changes fluid viscosity
Uploaded: 2025-02-13T15:43:08.000Z
Duration: 1 min 19 s
Channel: JoVE

A viscosidade mede como um fluido resiste ao fluxo devido ao atrito interno quando as camadas do fluido se movem umas sobre as outras.
Por exemplo, o mel flui lentamente porque tem alta viscosidade, enquanto a água flui facilmente com baixa viscosidade.
Existem dois tipos principais de viscosidade: dinâmica e cinemática. A viscosidade dinâmica mede a força necessária para mover uma camada de fluido sobre outra.
Por exemplo, quando mexido, o mel resiste mais à colher do que a água. A viscosidade cinemática é a razão entre a viscosidade dinâmica de um fluido e sua densidade, descrevendo como o fluido se espalha sob a gravidade.
Os fluidos mais comuns, como água e ar, têm uma viscosidade constante, independentemente da força aplicada.
No entanto, alguns fluidos, como o ketchup, mudam sua viscosidade dependendo da força aplicada; o ketchup flui mais facilmente quando a garrafa é agitada.
A temperatura afeta significativamente a viscosidade, crucial no projeto de dutos, onde o óleo deve fluir suavemente.
Em contraste, o ar quente em uma sauna demonstra como temperaturas mais altas aumentam a viscosidade dos gases.

viscosidade do fluido

A viscosidade mede a resistência que um fluido oferece ao fluxo e à deformação. Ela resulta do atrito interno entre camadas de fluido que se movem em relação umas às outras. A viscosidade dinâmica, denotada pela letra grega mu (μ), quantifica a força necessária para mover uma camada de fluido sobre outra. Para fluidos newtonianos como a água e ar, a relação entre a tensão de cisalhamento e a taxa de tensão de cisalhamento é linear, o que significa que sua viscosidade permanece constante independentemente da tensão aplicada. Fluidos não newtonianos, como ketchup, pasta de dente e areia movediça, apresentam uma viscosidade que muda com taxas de cisalhamento variáveis.

A temperatura afeta significativamente a viscosidade. Temperaturas mais altas diminuem a viscosidade para líquidos porque as forças intermoleculares enfraquecem, permitindo que o fluido flua mais facilmente. Um exemplo é o xarope aquecido, que derrama mais facilmente do que quando está frio. Por outro lado, temperaturas mais altas aumentam a viscosidade em gases, à medida que a atividade molecular e a troca de momento entre as camadas aumentam, semelhante a como o ar quente parece mais espesso em uma sauna.

Prever com precisão o comportamento do fluido requer considerar esses efeitos de temperatura, o que é crucial no projeto de sistemas como tubulações e motores de carro. Em tubulações, o óleo deve fluir suavemente, enquanto em motores de carro, a viscosidade correta do óleo garante lubrificação e eficiência adequadas. Esse entendimento ajuda os engenheiros a projetar e operar sistemas de forma mais eficaz sob temperaturas variáveis.

Viscosidade do Fluido

A viscosidade mede como um fluido resiste ao fluxo devido ao atrito interno quando as camadas do fluido se movem umas sobre as outras.
Por exemplo, o mel flui lentamente ...

Education

JoVE Core

Civil Engineering

Engenharia Civil

Unit 1

Unidade 1

Fluid Properties

Propriedades dos Fluidos

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

Viscosity of Fluid

how temperature changes fluid viscosity

Viscosity describes how much a fluid resists flow and deformation. It comes from internal friction between fluid layers that move past each other. Dynamic viscosity, shown by the Greek letter mu (μ), measures the force needed to move one layer over another.

Newtonian fluids, such as water and air, have a linear relationship between shearing stress and the rate of shearing strain. Their viscosity stays constant, even when the applied stress changes. Non-Newtonian fluids, like ketchup, toothpaste, and quicksand, do not behave this way. Their viscosity changes as the shear rate changes.

Temperature also has a strong effect on viscosity. For liquids, higher temperature lowers viscosity because intermolecular forces weaken and the fluid flows more easily. Heated syrup is a simple example. It pours more readily when warm than when it is cold.

For gases, the pattern is different. Higher temperature increases viscosity because molecular activity and momentum exchange between layers rise. Warm air can feel thicker, like the air in a sauna. Engineers need to account for these temperature effects when predicting fluid behavior.

This is important in systems such as pipelines and car engines. Oil in a pipeline must move smoothly. In a car engine, the right oil viscosity helps with lubrication and efficiency. Understanding viscosity helps engineers design and operate these systems under changing temperatures.

How Temperature Changes Fluid Viscosity

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Fluids include liquids and gases, and they behave differently from solids because of how their molecules are arranged. In solids, molecules are tightly packed and held by strong intermolecular forces. That structure helps solids keep their shape and resist deformation. Fluids have molecules that are farther apart and held by weaker forces. Because of this, they can flow and change shape easily. A fluid is any substance that deforms continuously when shearing stress is applied. Shearing stress...

density, specific weight, specific gravity and compressibility of fluid

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Fluid Properties: Density, Weight and Compression

Density, specific weight, specific gravity, and compressibility are key fluid properties. Density is the mass per unit volume of a fluid. It helps describe how much mass a fluid system contains and affects buoyancy, pressure, flow behavior, viscosity, thermal conductivity, and sound propagation. In pipeline design, knowing density helps engineers make sure the pipe can support the fluid’s mass. Specific weight is the weight per unit volume. It is found by multiplying density by gravitational...

viscosity of fluid

Viscosity describes how much a fluid resists flow and deformation. It comes from internal friction between fluid layers that move past each other. Dynamic viscosity, shown by the Greek letter mu (μ), measures the force needed to move one layer over another. Newtonian fluids, such as water and air, have a linear relationship between shearing stress and the rate of shearing strain. Their viscosity stays constant, even when the applied stress changes. Non-Newtonian fluids, like ketchup,...

types of fluids

Newtonian vs Non-Newtonian Fluid Behavior

Fluids can be grouped by how they respond to shear stress. Shear stress is a force that acts across a material, and shear strain rate describes how quickly it changes shape or flows. In this lesson, fluids are divided into Newtonian and non-Newtonian types. Newtonian fluids follow Newton’s law of viscosity. Their shear stress changes in a linear way as the shear rate changes. That means their viscosity stays constant, so their flow is predictable and easier to analyze. Water, air, oil, and...

newtonian fluid: problem solving

Newtonian Fluid Viscosity and Shear Stress

Newtonian fluids have a constant viscosity, so their shear stress and shear strain rate stay directly proportional. This creates a linear, predictable link between force and flow. Water, air, and light oils are common examples of Newtonian fluids. A simple way to study this behavior is to place the fluid between two parallel plates. One plate stays still, and the other moves at a constant velocity. The fluid forms a velocity gradient, which is the change in speed across the distance between...

vapor pressure of fluid

Vapor Pressure and Boiling Behavior

Vapor pressure and boiling behavior are closely linked in fluids. Vapor pressure is the pressure a vapor exerts when it is in thermodynamic equilibrium with its liquid at a given temperature. It shows how strongly molecules tend to leave the liquid surface and move into the vapor phase. A closed container helps show how vapor pressure forms. If a liquid sits in a sealed space with a small air gap, and that space is evacuated, vapor molecules escape from the liquid into the empty space. The...

surface tension of fluid

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capillarity in fluid

Capillary Action in Narrow Spaces

Capillary action is the movement of liquid through narrow spaces without any outside force. It depends on surface tension and adhesion between the liquid and nearby solid surfaces. This effect is common in narrow tubes, porous materials, and fine particles. Surface tension comes from cohesive forces between liquid molecules at the liquid-air boundary. These forces create a thin skin that resists outside pressure. When a capillary tube is placed in a liquid, the liquid level changes because of...

design example: deciding thickness of lubricating fluid in a shaft

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Lubricant Film Thickness for Shaft Bearings

Lubricant film thickness for shaft bearings is calculated to keep a rotating shaft from touching its bearing housing. A controlled layer of lubricant reduces friction, wear, and energy loss. It also helps the machine run smoothly by preventing metal-to-metal contact. The calculation starts with the shaft’s tangential velocity. First, the rotational speed is converted to angular velocity. Then that value is multiplied by the shaft radius. The result is the shaft’s linear speed at its surface...

key terms and concepts

Learn how viscosity changes with temperature in liquids and gases, and why Newtonian and non-Newtonian fluids matter in pipelines and car engines.

How Temperature Changes Fluid Viscosity | 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

How Temperature Changes Fluid Viscosity

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