Name: tracking fluid through space or mass
Uploaded: 2025-02-13T15:43:18.000Z
Duration: 1 min 16 s
Channel: JoVE

제어 볼륨은 질량, 에너지 또는 운동량과 관련된 상호 작용이 분석되는 공간에서 정의된 영역입니다.
파이프를 통해 흐르는 물을 생각해 보십시오. 제어 체적은 파이프의 한 부분이고 제어 표면은 이 섹션의 경계가 됩니다.
물이 이 제어 부피로 들어오고 나갈 때 질량, 운동량 및 에너지에 대한 보존 법칙을 사용하여 개별 물 입자를 추적하지 않고 흐름을 연구합니다.
유체가 이를 통과하는 동안 제어 볼륨은 고정된 상태로 유지되어 복잡성을 줄입니다.
대조적으로, 시스템은 시간이 지남에 따라 따라오는 특정 유체 질량을 나타냅니다. 고정된 양의 물을 담고 있는 물탱크를 생각해 보십시오.
탱크 내부의 물은 시스템을 나타냅니다. 물이 배수되거나 채워지면 동일한 물 시스템을 추적하여 시간 경과에 따른 동작과 변화에 초점을 맞춥니다.
시스템 표현을 사용하면 탱크의 상태가 변경되는 경우에도 이 고정된 물 질량을 분석할 수 있습니다.
시스템이 특정 유체 질량을 따르는 동안 제어 볼륨 접근 방식은 고정된 상태로 유지되고 공간의 특정 영역에 초점을 맞춥니다.

제어 볼륨 및 시스템 표현

질량, 에너지 및 운동량 전달을 분석하는 데는 제어 볼륨 접근 방식과 시스템 접근 방식이라는 두 가지 주요 프레임워크가 사용됩니다. 이러한 프레임워크는 공간의 특정 영역(제어 볼륨 접근 방식)에 초점을 맞추는지 또는 정의된 유체 질량(시스템 접근 방식)에 초점을 맞추는지에 따라 다른 관점을 제공합니다.

제어 볼륨 접근 방식은 유체가 흐르는 공간의 고정 영역을 고려합니다. 이 영역은 제어 표면으로 경계가 지정됩니다. 예를 들어, 파이프를 흐르는 물의 경우 제어 볼륨은 파이프의 고정된 섹션이고 제어 표면은 이 섹션의 경계가 됩니다. 이 프레임워크는 제어 볼륨 전체에 걸쳐 질량, 에너지 및 운동량에 대한 보존 법칙을 적용하여 유체 흐름 분석을 간소화합니다. 주요 장점은 개별 유체 입자를 추적할 필요 없이 유체의 거시적 특성에 초점을 맞춘다는 것입니다. 물이 제어 볼륨에 들어오고 나갈 때 흐름 특성의 변화가 제어 표면의 경계에서 평가되므로 정상 또는 비정상 흐름 조건을 연구하는 데 강력한 도구가 됩니다.

반면, 시스템 접근법은 시간에 따라 추적되는 고정된 유체 질량과 관련이 있습니다. 이에 대한 실제적인 예는 탱크 안의 물입니다. 탱크 안의 물은 시스템을 나타내며, 물이 빠지거나 채워질 때 동일한 질량의 물이 분석됩니다. 시스템의 동작은 외부 힘과 에너지 전달이 유체 상태를 변화시킬 때 연구됩니다. 이 접근법은 폐쇄 시스템 열 전달이나 상 변화 시나리오와 같이 정확한 질량과 에너지 또는 운동량 함량이 중요한 열역학적 프로세스를 분석할 때 특히 유용합니다.

제어 볼륨이 공간에 고정되어 표면을 통한 양의 교환에 초점을 맞추는 반면, 시스템 접근법은 특정 유체 질량의 진화를 추적합니다. 이러한 방법론은 상호 보완적이며 유체 역학 및 열역학 분석에 유연성을 제공합니다.

제어 볼륨은 질량, 에너지 또는 운동량과 관련된 상호 작용이 분석되는 공간에서 정의된 영역입니다.
파이프를 통해 흐르는 물을 생각해 보십시오. ...

control-volume-and-system-representations

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Fluid Kinematics

유체 운동학

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 example. In that case, the control volume is a fixed section of the pipe.

This method makes it easier to apply conservation laws for mass, energy, and momentum. It does not require tracking each fluid particle. Instead, it studies how fluid enters and exits the control surface. This makes it useful for both steady flow and unsteady flow.

The system approach uses a different viewpoint. It tracks a specific mass of fluid as conditions change. Water in a tank is a good example. As the tank drains or fills, the same mass of water is treated as the system.

This approach is especially useful in thermodynamics. It helps when the exact mass and its energy or momentum content matter, such as in closed-system heat transfer or phase change. The system changes because external forces and energy transfers act on it.

Together, the control volume and system approaches give students flexible ways to study fluid dynamics and thermodynamics. One focuses on what crosses a boundary in space. The other focuses on how one mass of fluid changes over time.

Tracking Fluid Through Space or Mass

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

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...

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

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

Learn how the control volume and system approaches analyze mass, energy, and momentum in fluids, using examples like water in a pipe or tank.

Tracking Fluid Through Space or Mass | 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.

Tracking Fluid Through Space or Mass

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