电大流体力学期末重点复习试题资料参考选择判断问答.doc

一、选择
1、在明渠均匀流中取一六面体，其所受的外力：作用在该六面体上有（正压力、切向力、重力）
2、在水箱上接出一条等直径长细圆管，末端设有阀门以控制流量，若水箱内水面不随时间变化，当阀门开度一定时，管中水流为（恒定均匀流）
3、 对实际流体，总水头总是（沿程下降）
4、按短管进行水力计算的管路是（虹吸管）
5、跌水的形成条件是（从缓流过渡到急流）
1．在明渠均匀流中取一六面体，其所受的外力：作用在该六面体上有（正压力、切向力、重力 ）
2．在水箱上接出一条等直径长细圆管，末端设有阀门以控制流量，若水箱内水面不随时间变化，当阀门开度一定时，管中水流为（恒定均匀流 ）
3．对实际流体，总水头总是（沿程下降）
4.按短管进行水力计算的管路是（虹吸管 ）
5.跌水的形成条件是 （ 从缓流过渡到急流 ）
1．在静水中取一六面体，分析其所受的外力：作用在该六面体上的力有(正压力、重力)。
2．在水箱上接出一条逐渐收缩锥形管道，末端设有阀门已控制流量，当水箱内水面不变、阀门开度一定时，管中水流为(非恒定非均匀流)。
3．按短管进行水力计算的管路是(虹吸管)
4．外延管嘴的正常工作条件是(管长l=(3-4)d，作用水头小于9米水柱)。
5．两段长直的棱柱形渠道，通过的流量相同，(粗糙系数不同(n1>n2)，其他参数相同(i，b，m，Q)，则h01>h02)。
1．在静水中取一六面体，分析其所受的外力：作用在该六面体上的表面力有(正压力)
2．在水箱上接出一条逐渐收缩锥形管道，末端设有阀门以控制流量，当水箱内水面不变、阀门开度一定时，管中水流为(恒定非均匀流)
3．等直径圆管中层流的过流断面流速分布是( 呈抛物线分布 )
4．流体内部某点压强为2个工程大气压，用液柱高度为(20米水柱 )
5．总水头线与测压管水头线的基本规律之一，是：(总水头线总是在测压管水头线的上方)
1．流体运动的连续性方程是根据（质量守恒）原理导出的。
2．判断层流和紊流的临界雷诺数是(下临界雷诺数)
3．圆管的水力半径为
二、判断题
1.流体内部切应力的大小仅与流速梯度有关。 （ × ）
2.真空压强是指没有大气存在时的压强。 （ × ）
3.均匀流一定是恒定流。 （ √ ）
4.动能修订系数与断面流速分布有关 （ √ ）
5.壁面光滑的管道一定是水力光滑管 （ × ）
6.若两孔口形状、尺寸完全相同，作用水头相同，一个为自由出流，一个为淹没出流，二者的流量是相同的 （ √ ）
1.流体内部切应力的大小仅与流速梯度有关。 （ × ）
2.真空压强是指没有大气存在时的压强。 （ × ）
3.均匀流一定是恒定流。（ √ ）
4.动能修订系数与断面流速分布有关 （ √ ）
5.壁面光滑的管道一定是水力光滑管 （ × ）
6.若两孔口形状、尺寸完全相同，作用水头相同，一个为自由出流，一个为淹没出流，二者的流量是相同的 （ √ ）
1．非均匀流一定是非恒定流。 (×)
2．流体内部切应力的大小仅与流速梯度有关。 ( × )
3．壁面光滑的管道一定是水力光滑管。 (×）
4．流体中某点的静压强大小与受压面方位无关。 ( √ )
5．明渠水流，从急流过渡到缓流，发生跌水(水跌)。 ( ×)
6．明渠水流的测压管水头线不可能沿程上升。 ( × )
1．理想流体与实际流体的区别仅在于，理想流体具有不可压缩性。( × )
2．无论流体作何种运动，流体内任何一个水平面都是等压面。(× )
3．在恒定流情况下，流线与迹线重合。( √ )
4·对于渐变流，过流断面上动水压强分布符合静水压强分布规律( √ )
5．壁面粗糙的管道一定是水力粗糙管。( × )
6．在进行水力计算时，短管是指管道几何长度较短的管道。( × )
1．实际流体在等直径长管中流动时的总水头线是水平的直线。（× ）
2．流体内切应力方向与流体运动方向相同。（ 错误 ）
3．等压面与质量力垂直。（ 正确 ）
4．阻力平方区内阻力系数与雷诺数无关。（ 正确 ）
三、简答题（共5小题 ，每题10分，共50分）
1流体静压强的两个特征？（1）垂直指向受压面。（2）某点压强的大小与受压面的方位无关（某点压强的大小仅与该点的淹没深度有关）
2、根据尼古拉兹试验，说明紊流各区沿程阻力系数 与Re和K/d的关系？（1）水力光滑区：××＝f（Re）（2）过渡粗糙区： ＝f（Re,K/d）(3)粗糙区： ＝f（K/d0）
3、为什么对于孔口淹没出流无小孔口与大孔口的区别？在划分小孔口和答孔口时，若H/d>10,视为孔口各点的压强仅似相等，定义为小孔口，对于孔口淹没出流其作用水头H为上下游水面差，孔口各点的压强相等，故对于孔口淹没出流无小孔口与大孔口之分。
4、何种流动为恒定流？若流体中任一点的运动要素与时间无关，或者说：流体中任一点的运动要素不随时间变化。
5、圆管中层流与紊流，其断面流速分布有什么不同？圆管中层流断面流速分布为抛物线状，而圆管中紊流断面流速分布为对数曲线，紊流的断面流速分布均匀化了。
1流体静压强的两个特征？（1）垂直指向受压面。（2）某点压强的大小与受压面的方位无关（某点压强的大小仅与该点的淹没深度有关）
2.根据尼古拉兹试验，说明紊流各区沿程阻力系数 与Re和K/d的关系？答：（1）水力光滑区：××＝f（Re）（2）过渡粗糙区： ＝f（Re,K/d）(3)粗糙区： ＝f（K/d0
3.为什么对于孔口淹没出流无小孔口与大孔口的区别？答：在划分小孔口和答孔口时，若H/d>10,视为孔口各点的压强仅似相等，定义为小孔口，对于孔口淹没出流其作用水头H为上下游水面差，孔口各点的压强相等，故对于孔口淹没出流无小孔口与大孔口之分。
4.何种流动为恒定流？若流体中任一点的运动要素与时间无关，或者说：流体中任一点的运动要素不随时间变化。
5.圆管中层流与紊流，其断面流速分布有什么不同？
圆管中层流断面流速分布为抛物线状，而圆管中紊流断面流速分布为对数曲线，紊流的断面流速分布均匀化了。
1．动力粘滞系数∥和运动粘滞系数v布什么区别?两者都反映流体的粘滞性，为动力量，v为运动量，，量纲不同。
3．简述明渠恒定非均匀流的水力特征。
答：①过水断面面积A，水深h，沿程改变。即
②底坡线，水面线，总线头线三线不再平行，即。
1．等压面是水平面的条件有哪些?答：(1)必须是同一种流体。(2)必须是连续流体。 (3)必须是单一重力作用条件下。(4)必须为静止流体。 (5分)
2．管道内流态为紊流时，水力光滑与水力粗糙是如何定义的?答：固体边界表面存在当量粗糙度K，流体运动时在固体边界存在粘性底层艿； (1)当粘性底层艿远远大于当量粗糙度K(K-<0．4a)，粘性底层完全掩盖当量粗糙度K，称为水力光滑。 (3分)(2)当粘性底层不能掩盖当量粗糙度K时(K>6δ)，称为水力粗糙 (2分)
1． 流体力学中连续介质假定的含义是什么？。
答案：流体是一个紧挨着一个的连续的质点所组成的，没有任何空隙的连续体，即所谓的“连续介质”。同时认为，流体的物理力学性质，例如密度、速度、压强和能量等，为空间坐标和时间的连续函数。
2． 描述流体运动的两种方法是什么？简述其内容。
答案：（1）拉格朗日法：以流体质点为研究对象，研究质点空间位置随时间的变化过程。（2）欧拉法：以流体空间位置的质点为研究对象，研究在确定位置上，流体质点速度随时间的变化过程。
3．简述尼古拉兹实验中沿程阻力系数λ的变化规律。
答案：通过尼古拉兹实验发现：在层流中λ仅是雷诺数Re的函数并与Re成反比；在层流到紊流过渡区，λ仅是Re的函数；在紊流光滑区λ=f1（Re），过渡区λ=f2（Re， ），粗糙区λ=f3（ ），紊流粗糙区又称阻力平方区。
4.在渗流计算中达西定律与杜比公式有何区别？
答案：达西定律适用于任一点的渗流流速u=kJ，其适用于恒定均匀层流渗流；而杜比公式是适用于恒定非均匀渐变层流渗流，同一过水断面上各点的渗流流速都相等且等于v= kJ。

Visa-free policy brings Chengdu biz, tourism boost. Making national headlines several times, Chengdu's 72-hour visa-free policy has attracted wide attention from both Chinese and foreign experts and businessmen since it took effect on Sept 1 last year. The program permits citizens from 51 countries and regions including the United States, Australia, Canada and Japan who have valid visas and flight tickets to a third country to spend three days in the city. The capital of Sichuan province is the first city in the western region of China to offer foreign tourists a three-day visa and the fourth nationwide to adopt the policy following Shanghai, Beijing and Guangzhou. Li Zhiyong, deputy dean of the tourism institute at Sichuan University, said the move "contributes to a large increase in the number of overseas tourists and raises the city's level of internationalization". "The policy will also bring direct economic revenue," Li said. "Chengdu has many cultural legacies and is also a paradise for panda lovers with the world's largest breeding and research center. Three days are long enough for foreign visitors to visit those iconic tourist spots," he noted. The city is home to the remains of the Jin sha civilization that dates back more than 3,000 years as well as the Qing cheng Mountains and the Du jiang yan irrigation system. Qing cheng has long been recognized as the birthplace of Taoism, China's ancient indigenous religion, while Du jiang yan is considered to be the oldest functioning water-control project in the world. Chengdu ranked third in tourist facilities, management and services among 60 Chinese cities in a customer satisfaction survey released last year. But, Li added that efforts are still needed to develop more tourism products, improve English services and provide accurate translation of traffic signs and scenic billboards. Zhao Yun, chairwoman of British Chamber of Commerce Southwest China, told China Daily that his colleagues found the policy very convenient. "A British client once flew here and stayed for just one day to check her ordered goods," she said. Zhao was born in Shanxi province, but she has lived in Chengdu for more than 10 years. "My life was like a running race moving from place to place. I also lived in Beijing and Shanghai before," she said. "But Chengdu is a place that you never want to leave once settling down. It is now my second hometown," she said. If the environment is further improved, the city will attract more people to visit and live, with the 72-hour visa-free policy and compelling conditions in transportation, culture, climate and cuisine, he said. Foreigners also gave positive feedback on the policy. A spokesman from Dell Inc said the company has a global hub of operation in Chengdu, so the three-day visa "has an immediate and positive influence on the company's business development". Rudy Buttignol, president of the public broadcasting company in British Columbia, Canada, said his work requires frequent travel to Chengdu and the policy "makes the trips easier". Data from the city's public security bureau shows some 100 foreign visitors enjoyed the 72-hour policy by the end of March, most of them from the United States, the United Kingdom and Germany. Chengdu also reported robust growth in its overall tourist industry last year. Official statistics show that it received some 150 million tourists last year, an increase of 28 percent from 2012. Around 1.7 million came from abroad, an increase of 12 percent. Total revenue from tourism surpassed 133 billion yuan ($21.7billion). During his visit to Kazakhstan in September, Chinese President Xi Jinping proposed that China and Central Asia join hands to build a Silk Road economic belt to boost cooperation. The idea has been widely echoed in Central Asian countries, becoming an encouraging blueprint for Chinese areas along the Silk Road that has linked Asia and Europe for more than 2,000 years. In the next three weeks, China Daily reporters will travel through the belt in China and in Kazakhstan, Uzbekistan and Turkey. They will show the progress and expectations of the countries, businesses and peoples on the route. Shaanxi - the start of the ancient Silk Road - has positioned itself as the new starting point for the development of the Silk Road Economic Belt, which will strengthen China's cooperation with Central Asian countries, a senior official said.
Shaanxi Governor Lou Qinjian said the province is fresh, rich and unique, as it was when it anchored one end of the ancient Silk Road.
"It is the best option for accommodating industrial transfers from East China or the world at large," he said on Wednesday in Xi'an.
Lou held a joint interview with 27 media, including China Daily, the first in a series of interviews entitled Chinese Media Along the Silk Road. The interviews will be in Shaanxi and Gansu provinces and the Xinjiang Uygur autonomous region, as well as Kazakhstan, Uzbekistan and Turkey.
The media group held the first interview on Wednesday morning in Xi'an, the starting point of the ancient Silk Road, a trade channel established more than 2,000 years ago linking China, Central Asia and Europe.