1-2-1 流体流动

He studied the change in a flow along a pipe when it goes from laminar flow to turbulent flow. In 1886 he formulated a theory of lubrication. Three years later he produced an important theoretical model for turbulent flow and it has become the standard mathematical framework used in the study of turbulence. His studies of condensation and heat transfer between solids and fluids brought radical revision in boiler and condenser , while his work on turbine pumps permitted their rapid development. A paper published in 1883 entitled "An experimental investigation of the circumstances which determine whether the motion of water in parallel channels shall be direct or sinuous and of the law of resistance in parallel channels" introduced what is now known as the 'Reynolds number', a variable commonly used in modeling fluid flow. Reynolds became a Fellow of the Royal Society in 1877 and, 11 years later, won their Royal Medal. In 1884 he was awarded an honorary degree by the University of Glasgow. By the beginning of the 1900s Reynolds health began to fail and he retired in 1905. Not only did he deteriorate physically but also mentally, which was sad to see in so brilliant a man who was hardly 60 years old. ... Despite his intense interest in education, he was not a great lecturer. His lectures were difficult to follow, and he frequently wandered among topics with little or no connection. Lamb, who knew Reynolds well both as a man and as a fellow worker in fluid dynamics, wrote:- The character of Reynolds was like his writings, strongly individual. He was conscious of the value of his work, but was content to leave it to the mature judgment of the scientific world. For advertisement he had no taste, and undue pretension on the part of others only elicited a tolerant smile. To his pupils he
第一章 流体流动
课程要求：
算。
正确理解流体流动过程中的基本原理及流体在管内的流动规律； 重点掌握流体静力学基本方程式、连续性方程式和柏努利方程式及其应用； 正确理解流体的流动类型和流动阻力的概念； 熟练掌握流体流动阻力的计算、简单管路的设计型计算和操作型计算； 了解测速管、文丘里流量计、孔板流量计和转子流量计的工作原理和基本计
Reynolds held this post until he retired in 1905. His early work was on magnetism and electricity but he soon concentrated on hydraulics and hydrodynamics. He also worked on electromagnetic properties of the sun and of comets, and considered tidal motions in rivers. After 1873 Reynolds concentrated mainly on fluid dynamics and it was in this area that his contributions were of world leading importance.
2.常见流体的粘度
表 1.3.1常见流体的粘度
单位：厘泊(cP)
3.粘度的测量方法
奥斯特瓦德粘度计法 落球粘度计法 纺槌粘度计法 同心圆粘度计法
流体
0℃
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20℃
40℃
60℃
80℃
苯 四氯化碳
酒精 乙醚 水银 水
空气
0.912 1.329 1.773 0.284 1.685 1.792 0.0166
0.652 0.969 1.200 0.233 1.554 1.002 0.0178
was most generous in the opportunities for valuable work which he put in their way, and in the share of cooperaDtior.nL. u S.S. ®
一、层流与扰流的定义
1.层流(laminar flow)：当流体流动时，各质点间互相平行，不相干扰者。
2.湍流(turbulent flow)：流体除了向前流动外，并碎成许多漩涡，而与侧边的流体混合者。 3.过渡流(transition flow)：是从层流过渡至扰流的中间状态，流体行为不稳定，时而层流时而扰流。
二、雷诺数
1.雷诺数(Reynold number)，是判断流体流动形态的指针。
2.雷诺数的定义为
0.503 0.739 0.834 0.197 1.450 0.656 0.0183
0.392 0.585 0.592 0.140 1.367 0.469 0.0192
0.329 0.468
0.118 1.298 0.357 0.0201
Dr. Lu S.S. ®
Jean-Louise Marie Poiseuille (1797-1869)
之，气体因粘度小，较易形成扰流流动。 (3)粘度的单位： CGS制：泊或厘泊，泊(poise，简写 P)，厘泊(centi-Poise，简写cP) SI 制：Pa．s 换算 1P=1g/(cm．s)=100cP。 1Pa．s =10P=1,000 cP。 (4)最常用的单位是泊或厘泊 (5)常温下水的粘度约1cP(1mPa‧s)，空气的粘度约0.02cP。 (6)温度对粘度的影响：液体粘度随温度升高而减少；但气体粘度则随温度升高而增大。
As his father had before him, Reynolds was elected to a scholarship at Queens' College. He again took up a post with an engineering firm, this time the civil engineers John Lawson of London, spending a year as a practicing civil engineer. In 1868 Reynolds became the first professor of engineering in Manchester (and the second in England).
22.4.1797-26.12.1869
Dr. Lu S.S. ®
Osborne Reynolds (1842-1912)
Osborne was born in Belfast where his father was Principal of the Collegiate School there but began his schooling at Dedham when his father was headmaster of the school in that Essex town. After that he received private tutoring to complete his secondary education. He did not go straight to university after his secondary education, however, but rather he took an apprenticeship with the engineering firm of Edward Hayes in 1861. Reynolds, after gaining experience in the engineering firm, studied mathematics at Cambridge, graduating in 1867. As an undergraduate Reynolds had attended some of the same classes as Rayleigh who was one year ahead of him.
D：管内直径，[m]
：平均速度，[m/s]
ρ：密度，[kg/m3]
μ：黏度，[kg/m‧s，或Pa‧s]
3.雷诺数为一无因次群
4.圆管内的雷诺数
French physician who developed an improved method for measuring blood pressure. He also studied the flow of liquid through tubes, and found that rate of flow depended on the diameter and length of the tube and pressure difference between the end. He formulated an equation known as Poiseuille's law describing the relationship. The unit of viscosity (resistance to flow) is named the poise in his honor.
主要内容：
• 流体流动及其静力学原理 • 流体流动中的守恒定律：柏努利方程 • 阻力损失及其计算 • 管路计算
• 流速和流量的测量 • 非牛顿流体流动
Dr. Lu S.S. ®
粘度
1.粘度的意义 (1) 粘度(viscosity)：是流体分子间引力大小的指针。 (2) 粘度甚大的流体，如甘油、洗发精等，分子间引力大，流动缓慢，易以层流流动；反