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8. Pressure Field when Fluid is at Rest

This chapter covers the analysis of pressure fields in fluids at rest, examining the relationship between pressure, body forces like gravity, and the effects of hydrostatic equilibrium. It discusses the distinctions between gauge pressure and absolute pressure while introducing concepts such as hydrostatic pressure distribution and capillarity effects. The foundations laid here are crucial for understanding fluid behavior in both static and dynamic conditions.

Sections

Pressure Field when Fluid is at Rest

This section discusses the characteristics and derivation of the pressure field in a fluid at rest, highlighting key concepts such as pressure gradients and gauge pressure.

8. Section Overview

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8.1.1 Introduction to Control Volume

This section covers the concept of control volumes in fluid mechanics, focusing on pressure distribution and the principles that govern fluid behavior at rest.

8.1.2 Forces Acting on the Control Volume

This section discusses the forces acting on a fluid control volume at rest, emphasizing pressure distribution and the effects of body forces such as gravity.

8.1.3 Pressure Field as a Function of Coordinates

This section discusses the determination of the pressure field in a stationary fluid, emphasizing the relationship between fluid pressure and coordinates in a control volume.

8.1.4 Approximation of Pressure using Taylor Series

This section discusses the approximation of pressure fields in fluids at rest using Taylor series, highlighting the effects of gravity and pressure distribution in fluid mechanics.

8.1.5 Force Components due to Pressure

This section discusses the components of forces acting on a fluid at rest, focusing on pressure distribution defined by the gradient of pressure in three-dimensional coordinates.

8.1.6 Hydrostatic Equations

This section discusses the hydrostatic equations relevant to understanding pressure fields in fluids at rest, integrating concepts like gravity, pressure distribution, and measurement techniques.

Gauge Pressure and Vacuum Pressure

This section discusses the concepts of gauge pressure and vacuum pressure, including their definitions and the significance of measurement standards in fluid mechanics.

8.2 Section Overview

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8.2.1 Definitions and Measurement

This section explores the definitions and measurement methods related to fluid pressure, including the concepts of hydrostatic pressure and gauge pressure.

8.2.2 Atmospheric Pressure as a Datum

This section explores the concept of pressure in fluid at rest, the significance of atmospheric pressure as a datum, and calculations of gauge and vacuum pressures.

Pressure Distribution Equations

This section discusses the derivation and significance of pressure distribution equations in fluid mechanics, particularly in hydrostatic conditions.

8.3 Section Overview

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8.3.1 Alignment of Gravity with Coordinate Axes

This section discusses how pressure fields behave in fluids at rest, focusing on the alignment of gravity with coordinate axes and the implications for pressure distribution.

8.3.2 Pressure Variation in a Horizontal Plane

This section discusses the pressure distribution in a fluid at rest, focusing on how pressure varies in the z-direction while remaining constant in the x and y directions.

8.3.3 Integration of Pressure Functions

This section discusses how to derive the pressure distribution in a fluid at rest using control volumes and the concept of pressure functions based on Cartesian coordinates.

Virtual Fluid Balls Concept

This section discusses how pressure in a fluid at rest can be analyzed using control volumes, examining the pressure field as a function of spatial variables (x, y, z), and introducing concepts like gauge pressure and vacuum pressure.

8.4 Section Overview

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8.4.1 Pressure Calculation via Weight of Fluid Balls

This section explains how to calculate pressure in a liquid at rest by relating it to the weight of fluid columns and introduces fundamental principles such as gauge and absolute pressure.

Capillary Effect

The capillary effect describes how liquids rise or fall in small tubes due to surface tension and gravity, impacting pressure distribution.

8.8.5 Section Overview

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8.5.1 Forces in Capillary Action

This section discusses the dynamics of pressure in fluids at rest, focusing on the implications of pressure fields in capillary action.

8.5.2 Control Volume in Capillary Problems

This section examines the principles of pressure distribution in fluids at rest within control volumes, specifically addressing the roles of shear stress, body forces, and the significance of gauge and vacuum pressure in various fluid dynamics scenarios.

Mercury Barometer

This section discusses the principles of pressure measurement using a mercury barometer, including the concepts of gauge pressure, vacuum pressure, and the significance of pressure distribution in static fluids.

8.6 Section Overview

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8.6.1 Measurement of Atmospheric Pressure

This section discusses the measurement of atmospheric pressure, focusing on its functional definitions, variations during fluid rest, and applications in gauge and absolute pressure measurements.

Conclusion

This section summarizes key concepts related to pressure in fluid mechanics, including pressure fields, hydrostatic equations, and pressure measurement methods.

8.7 Section Overview

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8.7.1 Summary of Key Concepts

This section discusses how to derive the pressure field in fluids at rest, applying Pascal's law, including concepts of gauge and vacuum pressure.

Learning Objectives

  • Pressure in fluids acts normal to the surface in a fluid at rest.

  • Hydrostatic pressure changes linearly with depth in a fluid column.

  • Capillary action results from the balance between surface tension and weight of the fluid.

Key Concepts

Pressure Field

A spatial distribution of pressure values within a fluid determined by various forces acting on the fluid.

Hydrostatic Pressure

The pressure exerted by a fluid due to its weight when the fluid is at rest, varying linearly with depth.

Gauge Pressure

Pressure measured relative to local atmospheric pressure; positive when above atmospheric pressure and negative (vacuum) when below.

Capillarity

The ability of a liquid to flow in narrow spaces without external forces, influenced by surface tension and adhesion to surfaces.

Control Volume

A specified region within space through which fluid flows for analyzing fluid motion, forces, and pressure distributions.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting

1 more question available

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