曾空 第五章管中流动 §5 5-1引言 管中不可压缩流体的运动规律,其中有许多基本概念对 于绕流或明渠流动也是适用的,管中流动所涉及的问题包括 流动状态、速度分布、起始段、流量和压强的计算、能量损 失等等
6 第五章 管中流动 §5-1 引言 管中不可压缩流体的运动规律，其中有许多基本概念对 于绕流或明渠流动也是适用的，管中流动所涉及的问题包括 流动状态、速度分布、起始段、流量和压强的计算、能量损 失等等
Flowing in pipe 85-2 Reynolds Experiment Reynolds number delegates inertia force and viscosity force. Reynolds number is different the ratio of the two kinds of forces are different too Therefore two kinds of flow states the interior structure and motion character of them are completely different, are produced The experimental apparatus are shown in Figure 5-1 which are composed mainly by the constant water level container A and glass pipe B. The entry part of glass pipe is connected by slippy bell mouth and the flux in pipe is adjusted by valve C. In the small container d there is colored liquid whose density is close to water. The colored liquid flows into glass pipe B via the tubule e to demonstrate the water state hi# AE B 且2 (a) (b)(c) Figure 5-1 Reynolds 7 experimental apparatus
7 §5-2 Reynolds Experiment Reynolds number delegates inertia force and viscosity force . Reynolds number is different, the ratio of the two kinds of forces are different too. Therefore , two kinds of flow states, the interior structure and motion character of them are completely different , are produced . The experimental apparatus are shown in Figure 5—1 which are composed mainly by the constant water level container A and glass pipe B. The entry part of glass pipe is connected by slippy bell mouth and the flux in pipe is adjusted by valve C. In the small container D there is colored liquid whose density is close to water. The colored liquid flows into glass pipe B via the tubule E to demonstrate the water state. ( a ) ( b ) ( c ) A D E 1 B 2 C hf Figure 5—1 Reynolds experimental apparatus
着空 §5-2雷诺实验 雷诺数代表惯性力和粘性力。雷诺数不同,这两种力的 比值也不同,由此产生内部结构和运动性质完全不同的两种 流动状态 雷诺实验的装置如图5—1所示,主要由恒水位水箱A和玻璃 管B等组成。玻璃管入口部分用光湑喇叭口连接,管中的流量用 阀门C调节,小容器D内盛有与水的密度相近的有色液体,经细 管E流入玻璃管B,用以演示水流状态。 h, AE B 2 (b) 图5—1雷诺实验装置 8
8 §5-2 雷诺实验 雷诺数代表惯性力和粘性力。雷诺数不同，这两种力的 比值也不同，由此产生内部结构和运动性质完全不同的两种 流动状态。 雷诺实验的装置如图5—1所示，主要由恒水位水箱A和玻璃 管B等组成。玻璃管入口部分用光滑喇叭口连接，管中的流量用 阀门C调节，小容器D内盛有与水的密度相近的有色液体，经细 管E流入玻璃管B，用以演示水流状态。 ( a ) ( b ) ( c ) A D E 1 B 2 C hf 图 5—1 雷 诺 实 验 装 置
Flowing in pipe Phenomenon a. As velocity of fluid in pipe b is less the colored water in pipe presents a thin and welldefined straight stream tube, as shown in Figure 5-1 (a), declares that the flow is stable. This kind of flow state is called laminar flow b. As valve C enlarges gradually the velocity of flow in pipe Wing , as shown in Figure 5-1 (b) c Continue to augment the velocity of flow, the colored water mixes with the clean water around it quickly as shown in Figure 5-1 C ndication The motion trace of fluid particle is extremely irregular and the fluids mixed each other exquisitely. This kind of motion state is called turbulent flow
9 Phenomenon： Indication： a. As velocity of fluid in pipe B is less the colored water in pipe presents a thin and welldefined straight stream tube , as shown in Figure 5—1（a）, declares that the flow is stable. This kind of flow state is called laminar flow. b. As valve C enlarges gradually the velocity of flow in pipe reaches a certain critical value , the colored water begins to swing ,as shown in Figure 5—1（b）. c. Continue to augment the velocity of flow , the colored water mixes with the clean water around it quickly ,as shown in Figure 5—1 （c）. The motion trace of fluid particle is extremely irregular and the fluids mixed each other exquisitely . This kind of motion state is called turbulent flow
着空 现象 a.当管B内流速较小时,管内颜色水呈一细股界限分明的直 线流束,如图5—1(a),表明流动稳定,这种流动状态称为层 流。 b当阀门C逐渐开大使管中流速达到某一临界值时,颜色水 开始出现摆动,如图5—1(b) c继续增大流速,颜色水迅速与周围清水相搀混,如图5—1 (c)所示。 表明: 流体质点的运动轨迹是极不规则的,流体互相剧烈搀混,这 种运动状态称为紊流或湍流。 10
10 现象： 表明： a.当管B内流速较小时，管内颜色水呈一细股界限分明的直 线流束，如图5—1（a），表明流动稳定，这种流动状态称为层 流。 b.当阀门C逐渐开大使管中流速达到某一临界值时，颜色水 开始出现摆动，如图5—1（b）。 c.继续增大流速，颜色水迅速与周围清水相搀混，如图5—1 （c）所示。 流体质点的运动轨迹是极不规则的，流体互相剧烈搀混，这 种运动状态称为紊流或湍流