流 体 力 学 FLUID MECHANICS,双 语 课 程,Teacher: 雷 斌 Cellphone: 15697181070 E-mail: leibinwust.edu.cn,武汉科技大学-机械自动化学院-流体传动及控制研究所,2019/1/17,A Easy Problem: Could we live without water or air?,2019/1/17,Fluid everywhere,2019/1/17,Whats fluid mechanics?,It is the branch of applied mechanics concerned with the statics and dynamics of fluids. The analysis of the behavior of fluids is based on the fundamental laws of mechanics which relate continuity of mass and energy with force and momentum. Fluid mechanics vs. Solid mechanics: 1. The nature is much different to that of a solid, 2. In fluids we usually deal with continuous streams of fluid. In solids we only consider individual elements.,2019/1/17,Applications of Fluid Mechanics,App-1 : infusion apparatus 静脉输液器,2019/1/17,App-2 : toilet bowl 抽水马桶,2019/1/17,App-3 :hydraulic system 液压系统,2019/1/17,Wind energy,Tidal energy,App-4 : Renewable energy 可再生能源,2019/1/17,App-5 :,2019/1/17,Course Notes,Period: 28 （Lecture：24 Practice：4） Test: Exam 70%,Experiment 15%,Others 15% Book:FLUID MECHANICS, 金晓宏 等主编, 中国电力出版社, 2011 液压传动实验指导书,金晓宏 等主编, 中国电力出版社, 2009,2019/1/17,Content and period,Chapter 1. FLUID PROPERTIES 第一章 流体性质,2019/1/17,Outline,1.1 Definition of a fluid 1.2 Units and Conversion 1.3 Fluid Properties + 1.4 Perfect Gas # Homework,+: Detailed #: Brief,2019/1/17,1.1 流体定义,1.1 Definition of a fluid,2019/1/17,Whats fluid?,chocolate,water,cloud,oil,2019/1/17,In physics, a fluid is a substance that continually deforms under an applied shear stress, no matter how small it is.,流体是一种一受到切力作用（不论多么小）就会连续变形的物体。,Definition of a fluid,2019/1/17,Fluid classification: Liquid or Gas. The intermolecular ,int(:)mlekjul attraction of fluid is very small and its molecular motion is very intense, so the arrangement of its molecules is very loose.,Character of fluid: can not maintain certain shape and has the fluidity(流动性).,Classification & Character,2019/1/17,Solid & Fluid,Solid: withstanding the pressure, tension and shear force. Fluid: can only resist the pressure, can not resist any small tension and shear force.,Fluid can not maintain its certain shape, and will deform continuously.,2019/1/17,Liquid: The distance between molecules of liquid is almost equal to the effective diameter （有效直径）of molecule. Liquid is often called incompressible fluid（不可压缩流体）.,Gas: The distance between the molecules is very large(3107), the order of magnitude of its molecules effective diameter is 108 centimeter. Gas is often called compressible fluid（可压缩流体）.,10-8: 10 to the power minus 8,Liquid & Gas,2019/1/17,Attention: When the compressibility is not referred, the laws in fluid mechanics are suitable to liquid as well as gas. When the compressibility is involved, the problem of gas and liquid must be dealt with individually.,2019/1/17,Continuum Hypothesis haipisis (连续性假设 ),In fluid mechanics, the physical quantities of macrofluid (宏观流体) (such as pressure, velocity and density) is the statistical average of the action and the behavior of most fluid molecules. In 1753, the continuous media was first proposed as macrofluid model by Euler（欧拉）：,The real fluid is considered as no-gap continuous media, called the basic assumption of continuity of fluid, or the continuum hypothesis of fluid.,2019/1/17,1.2 Units and Conversion,1.2 单位及换算,2019/1/17,International System of Units (SI, 国际单位制) newton (N) kilogram (kg) meter (m) second (s),The U.S. customary system of units, an Inch units pound (lb) - force slug(斯勒格，质量单位) - mass foot (ft) - length second (s) - time,(1.1),(1.2),1.2.1 System of Units,2019/1/17,Centimeter-gram-second system ( universal CGS unit 通用物理单位制，厘米-克-秒制),dyne(达因) - force gram (g) - mass centimeter (cm) - length second (s) - time,(1.3),2019/1/17,Table 1.1 SI unit, U.S. customary system unit, and conversion,1.2.2 Unit Conversion,2019/1/17,Abbreviations of SI units are written in lowercase letters (小写字母) for terms like hours (h), meters (m), and seconds (s). When a unit is named after a person, the abbreviation is capitalized(大写的）; examples are watt (W), pascal (Pa), and newton (N).,Table 1.2 Selected prefixes for powers of 10 in SI units,1.2.3 Abbreviations,bri:viein of SI units,2019/1/17,1.3 Fluid Properties,1.3 流体性质（重点）,2019/1/17,Mass force acting on the center of mass in a substance is proportional to the mass. m=V,(1) Mass forces,(a) The fluid is under the action of gravity （重力）G,(1.4),1.3.1 Forces on the Fluid,Figure 1.1 Free body in the fluid,2019/1/17,(b) The inertia force （惯性力）I is:,(1.5),Figure 1.2 A container filled with liquid in a linear motion,2019/1/17,(c) The centrifugal acceleration for point A of mass m is 2r and its centrifugal force (离心力) R is,(1.6),Figure 1.3 A rotating container,2019/1/17,The total mass force and resultant acceleration are expressed by W and q， respectively.,(1.7),(1.8),(1.9),the components（分量） of force,2019/1/17,If the mass force is only gravity an