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

점도는 유체 층이 서로를 지나갈 때 내부 마찰로 인해 유체가 흐름에 저항하는 방법을 측정합니다.
예를 들어, 꿀은 점도가 높기 때문에 천천히 흐르는 반면 물은 점도가 낮기 때문에 쉽게 흐릅니다.
점도에는 동적 및 운동학의 두 가지 주요 유형이 있습니다. 동적 점도는 한 유체 층을 다른 유체 층 위로 이동시키는 데 필요한 힘을 측정합니다.
예를 들어, 젓을 때 꿀은 물보다 숟가락에 더 저항합니다. Kinematic Viscosity는 유체의 동적 점도와 밀도의 비율로, 유체가 중력 하에서 어떻게 퍼지는지를 설명합니다.
물과 공기와 같은 가장 일반적인 유체는 가해진 힘에 관계없이 일정한 점도를 갖습니다.
그러나 케첩과 같은 일부 유체는 가해지는 힘에 따라 점도가 변합니다.케첩은 병을 흔들 때 더 쉽게 흐릅니다.
온도는 점도에 큰 영향을 미치며, 오일이 원활하게 흘러야 하는 파이프라인을 설계하는 데 매우 중요합니다.
대조적으로, 사우나의 따뜻한 공기는 온도가 높을수록 가스의 점도가 어떻게 증가하는지 보여줍니다.

유체의 점도

점도는 유체가 흐름과 변형에 대한 저항을 측정합니다. 이는 서로 상대적으로 움직이는 유체 층 사이의 내부 마찰로 인해 발생합니다. 그리스 문자 mu(μ)로 표시되는 동적 점도는 한 유체 층을 다른 유체 층 위로 옮기는 데 필요한 힘을 정량화합니다. 물과 공기와 같은 뉴턴 유체의 경우 전단 응력과 전단 변형률 사이의 관계는 선형이므로 점도는 적용된 응력에 관계없이 일정하게 유지됩니다. 케첩, 치약, 유사와 같은 비뉴턴 유체는 전단 속도에 따라 점도가 변합니다.

온도는 점도에 상당한 영향을 미칩니다. 온도가 높을수록 분자 간 힘이 약해져 유체가 더 쉽게 흐르기 때문에 액체의 점도가 감소합니다. 예를 들어, 차가울 때보다 더 쉽게 부어지는 가열된 시럽이 있습니다. 반대로 온도가 높을수록 분자 활동과 층 간의 운동량 교환이 증가함에 따라 가스의 점도가 증가합니다. 이는 사우나에서 따뜻한 공기가 더 두껍게 느껴지는 것과 유사합니다.

유체 거동을 정확하게 예측하려면 이러한 온도 효과를 고려해야 하며, 이는 파이프라인 및 자동차 엔진과 같은 시스템을 설계하는 데 중요합니다. 파이프라인에서는 오일이 원활하게 흐르고, 자동차 엔진에서는 올바른 오일 점도가 적절한 윤활 및 효율성을 보장합니다. 이러한 이해는 엔지니어가 다양한 온도에서 시스템을 보다 효과적으로 설계하고 운영하는 데 도움이 됩니다.

점도는 유체 층이 서로를 지나갈 때 내부 마찰로 인해 유체가 흐름에 저항하는 방법을 측정합니다.
예를 들어, 꿀은 천천히 흐른다 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Fluid Properties

유체 특성

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

characteristics of fluids

Fluid Behavior in Liquids and Gases

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

density-specific-weight-specific-gravity-and-compressibility-of-fluid

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

Why Water Drops and Needles Float

Surface tension helps explain why water forms drops, supports small objects, and moves in thin tubes. It is a property of fluids at the boundary between a liquid and a gas, or between two immiscible liquids. At the surface, molecules are pulled inward by neighboring molecules. That inward pull makes the surface act a little like a stretched elastic membrane. Inside a fluid, molecules are attracted in all directions. Surface molecules do not have the same balance of forces. They feel a net...

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

design-example-deciding-thickness-of-lubricating-fluid-in-a-shaft

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 offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

How Temperature Changes Fluid Viscosity

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