Chapter 1 Basic Concepts
　　第1章 基本概念
　　1.1 Introduction
　　Precise definitions of the basic concepts form the foundation for the proper development of a subject. Fluid mechanics has a unique vocabulary associated with it， like any other science. In this chapter， some important basic concepts associated with fluid mechanics are discussed. The unit systems and the law of dimensional homogeneity that will be used are also reviewed. Careful study of these concepts will be of great value for understanding the topics covered in the following chapters.
　　1.2 Some Basic Facts About Fluid Mechanics
　　Fluid mechanics may be defined as the subject dealing with the investigation of the motion and equilibrium of fluids. It is one of the oldest branches of physics and foundation for the understanding of many essential aspects of applied sciences and engineering. It is a subject of enormous interest in numerous fields such as biology， biomedicine， geophysics， meteorology， physical chemistry， plasma physics， and almost all branches of engineering.
　　Nearly two hundred years ago， man thought of laying down scientific rules to govern the motion of fluids. The rules were used mainly on the flow of water and air to understand them so that people can protect themselves from their fury during natural calamities such as cyclone and floods and utilize their power to develop fields like civil engineering and naval architecture. In spite of the common origin， two distinct schools of thought gradually developed. On one hand， through the concept of “ideal fluid”， mathematical physicists developed the theoretical science， known as classical hydrodynamics. On the other hand， realizing that idealized theories were of no practical application without empirical correction factors， engineers developed the applied science from experimental studies， known as hydraulics， for the specific fields of irrigation， water supply， river flow control， hydraulic power， and so on. Further， the development of aerospace， chemical， and mechanical engineering during the past few decades， and the exploration of space from 1960s have increased the interest in the study of fluid mechanics. Thus， it now ranks as one of the most-important basic subjects in engineering science.
　　1.1 引言
　　对基本概念的准确定义是一个学科正确发展的基础。和其他学科一样，流体力学也有一个与之相关的专业术语表。本章讨论与流体力学有关的一些重要基本概念，并对书中所涉及的单位制及量纲一致性原理进行综述。认真学习这些基本概念对后续章节内容的理解至关重要。
　　1.2 流体力学概况
　　流体力学可以被定义为一门研究流体运动和平衡规律的学科。流体力学是物理学古老的分支之一，也是理解应用科学和工程学许多基本原理的基础。在生物学、生物医学、地球物理学、气象学、物理化学、等离子体物理学等众多领域，以及几乎所有的工程学分支领域，流体力学都是非常受关注的学科。
　　大约两百年前，人们想到建立科学的定律来掌握流体的运动。这些定律主要用来理解水和空气的流动规律，从而使人类能够保护自己免受飓风和洪水等自然灾害的侵袭，并利用这些自然动力来发展土木工程和海事工程。尽管起源相同，但两个截然不同的流体力学学派逐渐发展了起来。一方面，数学物理学家们通过“理想流体”这一概念发展了流体力学理论科学，即经典流体力学。另一方面，工程师认识到不经过经验修正，理想化的理论就不实用，于是通过实验研究发展出用于灌溉、给水、河流控制、水力等专业领域的流体力学应用科学，即水力学。此外，航空航天、化学工程和机械工程在过去几十年的发展，以及20世纪60年代以来人类对外太空的探索，都进一步激发了人们对流体力学的研究热情。因此，流体力学已经成为工程科学中重要的基础学科之一。
　　The science of fluid mechanics has been extended into fields like regimes of hypervelocity flight and flow of electrical conducting fluids. This has introduced new fields of interest such as hypersonic flow and magneto-fluid dynamics. In this connection， it has become essential to combine the knowledge of thermodynamics， heat transfer， mass transfer， electromagnetic theory and fluid mechanics， for the complete understanding of the physical phenomenon involved in any flow process.
　　Fluid mechanics is one of the rapidly growing basic sciences， whose principles find application even in daily life. For instance， the flight of birds in air and the motion of fish in water are governed by the fluid mechanics rules. The design of various types of aircraft and ships is based on the fluid mechanics principles. Even natural phenomena like tornadoes and hurricanes can also be explained by the science of fluid mechanics. In fact， the science of fluid mechanics dealing with such natural phenomena has been developed to such an extent that they can be predicted well in advance. Since the earth is surrounded by an environment of air and water to a very large extent， almost everything that is happening on the earth and its atmosphere are some way or the other associated with the science of fluid mechanics.
　　流体力学已经拓展到超高速飞行和导电流体流动等范畴，并衍生出新的研究领域，例如高超声速流动和磁流体动力学。在这种拓展和演变背景下，将热力学、传热学、传质学、电磁理论与流体力学知识相结合，已经成为全面理解任何一个流动过程物理现象必不可少的手段。
　　流体力学是快速发展的基础科学之一，其原理甚至可应用于日常生活中。例如，空中鸟儿的飞翔和水中鱼儿的游动都符合流体力学规律。各种飞机和船舶的设计也要遵循流体力学原理。甚至像飓风和台风这样的自然现象也能用流体力学来解释。事实上，与这些自然现象相关的流体力学学科已经发展到能够很好地预测这些自然现象的程度。由于地球的绝大部分是被空气和水所包围的，因此地球上及大气中发生的一切几乎都或多或少和流体力学相关。
　　The science of fluid motion is referred to as the mechanics of fluids， an allied subject of the mechanics of solids and engineering materials， and built on the same fundamental laws of motion. Therefore， unlike empirical hydraulics， it is based on the physical principles， and has close correlation with experimental studies which both compliment and substantiate the fundamental analysis， unlike the classical hydrodynamics which

CONTENTS
Preface
Chapter 1 Basic Concepts 1
1.1 Introduction 1
1.2 Some Basic Facts About Fluid Mechanics 1
1.3 Fluids and the Continuum 5
1.4 The Perfect Gas Equation of State 7
1.5 Regimes of Fluid Mechanics 9
1.5.1 Ideal Fluid Flow 9
1.5.2 Viscous Incompressible Flow 10
1.5.3 Gas Dynamics 10
1.5.4 Rarefied Gas Dynamics 11
1.5.5 Flow of Multicomponent Mixtures 13
1.5.6 Non-Newtonian Fluid Flow 13
1.6 Dimension and Units 13
1.7 Law of Dimensional Homogeneity 14
1.8 Summary 17
1.9 Exercises 17
Chapter 2 Properties of Fluids 19
2.1 Introduction 19
2.2 Basic Properties of Fluids 19
2.2.1 Pressure of Fluids 20
2.2.2 Temperature 21
2.2.3 Density 22
2.2.4 Viscosity 23
2.2.5 Compressibility 28
2.3 Thermodynamic Properties of Fluids 29
2.3.1 Specific Heat 29
2.3.2 The Ratio of Specific Heats 30
2.3.3 Thermal Conductivity of Air 31
2.4 Surface Tension 32
2.5 Summary 34
2.6 Exercises 34
Chapter 3 Fluid Statics 36
3.1 Introduction 36
3.2 Scalar， Vector and Tensor Quantities 36
3.3 Body and Surface Forces 37
3.4 Forces in Stationary Fluids 38
3.5 Pressure Force on a Fluid Element 39
3.6 Basic Equations of Fluid Statics 40
3.6.1 Hydrostatic Pressure Distribution 41
3.6.2 Measurement of Pressures 43
3.6.3 Units and Scales of Pressure Measurement 46
3.7 The Atmosphere 46
3.7.1 The International Standard Atmosphere 47
3.7.2 Calculations on the Stratosphere 47
3.7.3 Calculations on the Troposphere 49
3.8 Hydrostatic Force on Submerged Surfaces 54
3.9 Buoyancy 56
3.10 Summary 57
3.11 Exercises 58
References 62
Chapter 4 Kinematics and Dynamics of Fluid Flow 63
4.1 Introduction 63
4.2 Description of Fluid Flow 63
4.2.1 Lagrangian and Eulerian Methods 63
4.2.2 Local and Material Rates of Change 64
4.2.3 Graphical Description of Fluid Motion 66
4.3 Basic and Subsidiary Laws 68
4.3.1 System and Control Volume 68
4.3.2 Integral and Differential Analysis 69
4.4 Basic Equation 69
4.4.1 Continuity Equation 70
4.4.2 Momentum Equation 70
4.4.3 Equation of State 72
4.4.4 Boundary Layer Equation 73
4.5 Rotational and Irrotational Motion 75
4.5.1 Circulation and Vorticity 75
4.5.2 Stream Function 76
4.5.3 Relationship Between Stream Function and Velocity Potential 77
4.6 Potential Flow 78
4.6.1 Two-Dimensional Source and Sink 81
4.6.2 Simple Vortex 82
4.6.3 Source-Sink Pair 84
4.6.4 Doublet 84
4.7 Flow Past a Half-Body—Combination of Simple Flows 88
4.8 Summary 97
4.9 Exercises 97
Chapter 5 Several Problems of Fluid Dynamics 114
5.1 Introduction 114
5.2 Viscous Flows 114
5.3 Drag of Bodies 117
5.3.1 Pressure Drag 118
5.3.2 Skin Friction Drag 124
5.3.3 Comparison of Drag of Various Bodies 125
5.4 Turbulence 128
5.5 Flow Through Pipes 136
5.6 Flow Past a Circular Cylinder Without Circulation 142
5.7 Flow Past a Circular Cylinder With Circulation 146
5.8 Summary 151
5.9 Exercises 151
References 162
Chapter 6 Boundary Layer 163
6.1 Introduction 163
6.2 Boundary Layer Development 164
6.3 Boundary Layer Thickness 167
6.3.1 Displacement Thickness 168
6.3.2 Momentum Thickness 170
6.3.3 Kinetic Energy Thickness 171
6.3.4 Non-Dimensional Velocity Profile 172
6.3.5 Types of Boundary Layer 173
6.4 Boundary Layer Flow 175
6.5 Boundary Layer Solutions 179
6.6 Momentum-Integral Estimates 179
6.6.1 Conservation of Linear Momentum 179
6.6.2 Karman’s Analysis of Flat Plate Boundary Layer 181
6.7 Boundary Layer Equations in Dimensionless Form 182
6.8 Flat Plate Boundary Layer 189
6.8.1 Laminar Flow Boundary Layer 190
6.8.2 Boundary Layer Thickness for Flat Plate 192
6.9 Turbulent Boundary Layer for Incompressible Flow Along a Flat Plate 201
6.10 Flows With Pressure Gradient 205
6.11 Laminar Integral Theory 206
6.12 Summary 214
6.13 Exercises 214
References 217
目录
前言
第1章 基本概念 1
1.1 引言 1
1.2 流体力学概况 1
1.3 流体和连续介质 5
1.4 完全气体状态方程 7
1.5 流体力学范畴 9
1.5.1 理想流体流动 9
1.5.2 黏性不可压缩流动 10
1.5.3 气体动力学 10
1.5.4 稀薄气体动力学 11
1.5.5 多元混合流动 13
1.5.6 非牛顿流体流动 13
1.6 量纲和单位制 13
1.7 量纲一致性原理 14
1.8 小结 17
1.9 习题 17
第2章 流体的性质 19
2.1 引言 19
2.2 流体的基本性质 19
2.2.1 流体压力 20
2.2.2 温度 21
2.2.3 密度 22
2.2.4 黏性 23
2.2.5 可压缩性 28
2.3 流体的热力学性质 29
2.3.1 比热 29
2.3.2 比热比 30
2.3.3 空气的导热性 31
2.4 表面张力 32
2.5 小结 34
2.6 习题 34
第3章 流体静力学 36
3.1 引言 36
3.2 标量、矢量和张量 36
3.3 体积力和表面力 37
3.4 静止流体中的力 38
3.5 流体微元上的压力合力 39
3.6 流体静力学基本方程 40
3.6.1 流体静压分布 41
3.6.2 压力测量 43
3.6.3 压力测量单位和尺度 46
3.7 大气 46
3.7.1 国际标准大气 47
3.7.2 平流层计算 47
3.7.3 对流层计算 49
3.8 浸没表面上的静压力 54
3.9 浮力 56
3.10 小结 57
3.11 习题 58
参考文献 62
第4章 流体运动学和动力学 63
4.1 引言 63
4.2 流体流动的描述 63
4.2.1 拉格朗日法和欧拉法 63
4.2.2 当地导数和随体（物质）导数 64
4.2.3 流体运动的图形化描述 66
4.3 基本定律和