Name: flow patterns by direction and time
Uploaded: 2025-02-13T15:43:18.000Z
Duration: 1 min 23 s
Channel: JoVE

フローは、ディメンションに基づいて分類できます。1次元の流れでは、速度や圧力などの特性は、まっすぐなパイプを通って移動する水に見られるように、一方向に沿って変化します。
2次元の流れには、開いた水路を流れる水など、長さと深さの両方に変化が伴います。
3次元の流れはより複雑で、建物を循環する風のように、3つの方向すべてに変化があります。
流れは、その速度と流体粒子の移動方法にも基づいて分類されます。最も一般的なタイプは、定常流れと非定常流れです。
都市水道システムのパイプラインを通過する水などの定常的な流れは、時間の経過とともに任意の時点で一定のままの流体特性を持っています。
雨水流出時の速度や流量の変化など、非定常的な流れは、時間の経過とともに流体特性に変化をもたらします。
もう一つの重要な違いは、層流と乱流です。層流は、水が低速で小さく滑らかなパイプを通って移動するような、滑らかで整然とした動きを特徴としています。
対照的に、乱流は、洪水時に河川や暗渠でよく見られる、混沌とした不規則な流体運動を伴います。

流れの種類の紹介

流体の流れは次元と動作によって分類されます。1 次元の流れは最も単純な形式で、速度や圧力などの特性は 1 つの軸に沿ってのみ変化します。直管を通る水の流れは、他の方向の変化が最小限であるため、この流れの種類の例です。1 次元解析は、パイプの長さに沿った変化のみに焦点を当てることで、このような流れの理解を簡素化するのに役立ちます。

 2 次元の流れでは、橋のデッキのような平らな表面を移動する空気のように、長さと高さの両方が変化します。変化は 2 方向に発生するため、1 次元の流れよりも計算が複雑になります。最も複雑な 3 次元の流れでは、長さ、高さ、深さの 3 つの空間次元すべてに変化が伴います。建物の周りを循環する風は、このタイプの流れを示しており、流体の特性が複数の方向で異なります。

 流れは、流体の特性が時間の経過とともにどのように変化するかによっても分類されます。定常流は、速度や圧力などの特性が時間の経過と共にどの時点でも一定のままである状況を表します。自治体の給水システムのパイプラインは、典型的な例です。対照的に、雨水流出などの非定常流は、時間の経過とともに流体特性が変化します。非定常流を分析するには、速度と圧力の時間依存の変化に注意する必要があります。

 層流と乱流の区別も重要です。層流は、流体層が最小限の混合で平行に移動する、滑らかで整然とした流体の動きが特徴です。土壌層を浸透する地下水は、多くの場合、層流を示します。ただし、乱流は、洪水時の川でよく見られる、混沌とした不規則な動きを伴います。流体粒子は複雑に相互作用し、渦巻きを作り出します。そのため、このような流れの分析は非常に複雑になります。

フローは、ディメンションに基づいて分類できます。1次元の流れでは、速度や圧力などの特性は一方向に沿って変化します。

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Fluid Kinematics

流体運動学

KEY TERMS AND CONCEPTS

主要用語と概念

Introduction to Types of Flows

flow patterns by direction and time

Fluid flow can be grouped by direction and by how it changes over time. The simplest case is one-dimensional flow. In this type, properties such as velocity and pressure change along only one axis. Water moving through a straight pipe is a common example, because changes in other directions are very small.

Two-dimensional flow changes in two directions. It varies in both length and height, so the analysis is more complex than one-dimensional flow. Air moving over a flat surface, such as a bridge deck, shows this pattern.

Three-dimensional flow is the most complex type. It involves changes in length, height, and depth. Wind moving around buildings is an example, since fluid properties can differ in multiple directions.

Flows are also classified by whether they stay the same over time. In steady flow, velocity and pressure remain constant at a point as time passes. A pipeline in a municipal water supply system is a typical example. Unsteady flow is different because fluid properties change over time. Stormwater runoff is one example, and it requires attention to time-dependent changes in velocity and pressure.

Another important split is between laminar and turbulent flow. Laminar flow is smooth and orderly, with fluid layers moving in parallel and very little mixing. Groundwater seeping through soil layers often follows this pattern. Turbulent flow is chaotic and irregular. It often appears in rivers during floods, where swirling eddies and vortices make the motion much harder to analyze.

Flow Patterns by Direction and Time

eulerian and lagrangian flow descriptions

eulerian-and-lagrangian-flow-descriptions

Tracking Fluid Motion in Space and Time

Fluid flow can be described with the Eulerian and Lagrangian methods. These two approaches give different views of the same moving fluid. They are useful in science and engineering because the best method depends on the problem being studied. The Eulerian method looks at fixed points in space. At each location, it measures fluid properties such as velocity, pressure, and temperature as the fluid moves past. This stationary view is useful when studying how a fluid interacts with a solid object.

introduction to types of flows

Fluid flow can be grouped by direction and by how it changes over time. The simplest case is one-dimensional flow. In this type, properties such as velocity and pressure change along only one axis. Water moving through a straight pipe is a common example, because changes in other directions are very small. Two-dimensional flow changes in two directions. It varies in both length and height, so the analysis is more complex than one-dimensional flow. Air moving over a flat surface, such as a...

streamlines, streaklines, and pathlines

Tracing Fluid Motion: Three Flow Paths

Streamlines, streaklines, and pathlines are three ways to describe fluid motion. Each one shows flow from a different angle. Together, they help students compare how a fluid moves in steady and unsteady flow. A streamline is a line that stays tangent to the fluid’s velocity vector at each point. That means the fluid velocity points along the streamline. Streamlines give an instant picture of the flow field, so they are useful for showing the overall direction of flow in a fluid system. In...

control volume and system representations

control-volume-and-system-representations

Tracking Fluid Through Space or Mass

Fluid analysis often uses two linked ideas: the control volume approach and the system approach. Both help describe mass, energy, and momentum transfer, but they focus on different things. One follows a region in space. The other follows a fixed mass of fluid over time. The control volume approach looks at a stationary area in space through which fluid moves. That area is bounded by a control surface, which is the outer edge of the region. A pipe with water flowing through it is a clear...

velocity and acceleration in steady and unsteady flow

velocity-and-acceleration-in-steady-and-unsteady-flow

How Flow Changes Affect Particle Motion

Velocity and acceleration help describe how a fluid particle moves in steady and unsteady flow. A fluid particle follows a pathline, and its velocity depends on both position and time. Acceleration is found by differentiating velocity with respect to time, so it shows how the particle’s motion changes. In a flow field, acceleration can be written using three perpendicular components. These components show how velocity changes over time in different spatial directions. This gives a general way...

reynolds transport theorem

Reynolds Transport and Control Volumes

Reynolds transport theorem links a fluid system to a control volume. It helps explain how the time rate of change of a property can be tracked in fluid dynamics. The theorem uses extensive properties, such as mass, velocity, acceleration, temperature, and momentum. These properties depend on the size of the system. Their intensive forms are the values per unit mass. The total amount of an extensive property in a system at any instant is the sum of the amounts carried by each tiny fluid...

design example: flow through a fire extinguisher

design-example-flow-through-a-fire-extinguisher

Fire Extinguisher Nozzle Flow and Pressure

A pressurized water fire extinguisher uses fluid dynamics to create a fast stream of water. The water is stored at a much higher pressure inside the extinguisher than the surrounding air. When the extinguisher is activated, that pressure difference forces water to flow out quickly. Bernoulli's equation helps predict the exit speed of the water. This equation links pressure and velocity. As pressure drops, velocity increases. In the extinguisher, the high internal pressure is converted into the...

key terms and concepts

Explore how fluid flow changes by direction and time, from one-dimensional and steady flow to turbulent motion in pipes, wind, and rivers.

Flow Patterns by Direction and Time | 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.

Flow Patterns by Direction and Time

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