Name: fluid properties: density, weight and compression
Uploaded: 2025-02-13T15:43:08.000Z
Duration: 1 min 27 s
Channel: JoVE

流体の密度は、単位体積あたりの質量として定義され、浮力、圧力分布、流れの挙動などの主要な流体特性を決定します。
たとえば、パイプラインを設計する場合、流体密度を正確に測定することで、パイプラインが流体の質量を処理できるようになります。
流体の比重は、単位体積あたりの重量を表し、流体の密度に重力加速度を掛けて計算されます。
比重は、材料の重量と体積の比例関係を定義し、パイプライン壁に流体が加える圧力を推定するのに役立ちます。
 比重は、特定の温度での流体の密度と水の密度を比較する無次元の尺度です。
システムのさまざまな流体を比較する場合、比重は最適な性能と安全性を備えた流体を選択するのに役立ちます。
体積弾性率は圧縮率を定量化し、圧力変化を体積ひずみに関連付けます。
液体は圧縮率が低いため、圧力下での体積変化が最小限に抑えられます。対照的に、ガスは圧縮性が高く、圧力変動に伴って大きな体積変化を示します。
油圧システムでは、圧力下で流体がどれだけ圧縮されるかを知ることは、効率と安全性にとって非常に重要です。

流体の密度、比重、比重、圧縮率

密度、比重、比重、圧縮率は、流体の基本的な特性です。密度は単位体積あたりの質量であり、流体システムの質量を特徴づけます。密度は、浮力、圧力、流動力学、粘性、熱伝導率、音の伝播に影響します。たとえば、パイプラインの設計では、正確な密度測定により、パイプラインが流体の質量を処理できることが保証されます。

 比重は単位体積あたりの重量を表し、密度に重力加速度を掛けて計算されます。この特性は、重量が体積によってどのように変化するかを示し、流体がパイプラインの壁に及ぼす力を推定するのに役立ちます。これは、構造の完全性を維持するために不可欠です。

 比重は、特定の温度での流体の密度と水の密度を比較する無次元の尺度です。この比較は、材料の選択に役立ち、互換性と効率を保証します。たとえば、比重は、単位の制約なしにさまざまなオプションを比較することで、システムに最適な流体を選択するのに役立ちます。

 圧縮率は、圧力下での流体の体積の変化を表します。体積弾性率はこの特性を定量化し、圧力変化と体積変化を関連付けます。液体は圧縮性が低いため、圧力がかかっても体積変化は最小限です。対照的に、気体は圧縮性が高く、圧力の変化に応じて体積が大きく変化します。この特性は油圧システムでは極めて重要であり、圧力下で流体をどの程度圧縮できるかを理解することで効率と安全性を確保できます。

流体の密度は、単位体積あたりの質量として定義され、浮力、圧力分布、流れの挙動などの主要な流体特性を決定します。
対して。。。

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

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Fluid Properties

流体の特性

KEY TERMS AND CONCEPTS

主要用語と概念

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 acceleration. This property shows how a fluid’s weight changes with volume. It also helps estimate the force a fluid exerts on pipeline walls, which matters for structural integrity.

Specific gravity is a dimensionless comparison between a fluid’s density and the density of water at a given temperature. Because it has no units, it makes it easier to compare fluids and choose materials that work well together. It can help identify the best fluid for a system without needing to work through unit-based calculations.

Compressibility describes how a fluid’s volume changes when pressure changes. The bulk modulus measures this property by linking pressure change to volume change. Liquids have low compressibility, so their volume changes very little under pressure. Gases are much more compressible and can change volume a lot. This matters in hydraulic systems, where safe and efficient operation depends on understanding how much the fluid can compress.

Fluid Properties: Density, Weight and Compression

fluid-properties-density-weight-and-compression

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 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

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,...

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 density, specific weight, specific gravity, and compressibility describe fluid behavior, from pipeline forces to hydraulic system safety.

Fluid Properties: Density, Weight and Compression | 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 Properties: Density, Weight and Compression

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