电大流体力学形成性考核册(答案4)

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1、专业好文档作业4 答案 (第7章、第8章、第9章、第10章)第7章一、选择题 1. 对于管道无压流，当充满度分别为（ B ）时，其流量和速度分别达到最大。A. 0.5, 0.5 B. 0.95, 0.81 C. 0.81, 081 D. 1.0, 1.02. 对于a, b, c三种水面线，下列哪些说法是错误（ A ）（ C ）A所有a、c型曲线都是壅水曲线，即，水深沿程增大。B所有b型曲线都是壅水曲线，即，水深沿程增大。C所有a、c型曲线都是降水曲线，即，水深沿程减小。D所有b型曲线都是降水曲线，即，水深沿程减小。3. 跌水的形成条件是（ D ） A.从急流过渡到急流 B.从急流过渡到缓流 C

2、.从缓流过渡到急流 D.从缓流过渡到缓流4水跃的形成条件是（ C ）A.从急流过渡到急流 B.从急流过渡到缓流C.从缓流过渡到急流 D.从缓流过渡到缓流5两段长直的棱柱形渠道，通过的流量相同,（ B ）A.粗糙系数不同（ ），其他参数相同（，则B.底坡不同（），其他参数相同（，则C.底宽不同（），其他参数相同（，则D.边坡系数不同（），其他参数相同（，则6. 一梯形断面渠道，底宽b=2m，边坡系数m=1.0，明渠中的水深h=0.5m, 则湿周、水力半径R分别为（ D ）A. 3.414, 0.366 B. 3.5, 0.30 C. 3.414, 0.30 D. 3.5, 0.366二、判断题

3、1、缓流一定是均匀流，急流一定不是均匀流。 （ 错误 ）2、断面单位能量沿程可大、可小，或者不变。（ 错误 ）3、明渠中均匀流一定是恒定流。（ 正确 ）4、明渠水流，从缓流到急流发生水跃。( 正确 )5谈到某水流是临界流、急流、缓流,这是以明渠断面尺寸、流量一定为前题而讲的。 （ 错误 ）6 明渠水流的测压管水头线不可能沿程上升。（ 正确 ）三、简答题1、简述明渠均匀流的水力特征及其形成条件。答: 明渠均匀流的水力特征:（1） 底坡线，水面线，总线头线三线平行，即，（2）水深，过水断面面积A，断面平均流速及断面流速分布沿程不变。明渠均匀流形成条件： 流量恒定。 必须是长直棱柱形渠道，糙率不变。

4、 底坡不变。1、 简述明渠水流的三种流态及其四个判别方法及标准。答: 明渠水流分为缓流、急流、临界流。个判别方法有： 干扰波：波速C=，=C为临界流，c为急流； 弗劳德数：弗劳德数Fr=，Fr=1临界流，Fr 1 缓流，Fr1 急流； 临界水深： 缓流，临界流， 急流， 临界底坡：缓流，临界流，急流。3. 写出佛劳德数的表达式，并说明其物理意义。答: 弗劳德数Fr= ，物理意义是:反映动能与势能之比。4. 为什么要引入断面单位能量的概念？答: 引入断面单位能量，目的是分析水面曲线的变化规律和建立临界流方程。5. 简述明渠恒定非均匀流的水力特征。答: 过水断面面积A，水深，沿程改变。即底坡线，水

5、面线，总线头线三线不再平行，即，一、 作图题 (略)1 下面为长直棱柱形渠道，n不变，试定性绘出可能出现的水面曲线型式。 二、 计算题1 某输水渠道，沙质土壤，岸边有杂草，糙率系数n=0.025, 底坡I=0.002, 断面为梯形，边坡系数m=1.0。 按水力最优断面设计，通过流量Q=0.8m3/s, 试确定其断面尺寸。解: （1）按水力最优断面条件计算宽深比。 （2）计算相关水力要素：过流断面积、水力半径。代入流量基本公式解出水深。（3）求出底宽。答案： 2 有两段矩形断面渠道相连，通过流量Q=2.8m3/s，底宽b=2m, 混凝土衬护，n=0.015, i1=0.012, i2=0.000

6、8。这两段渠道是否为水跃衔接？若是水跃衔接，是何种形式水跃？并定性绘图表示。 解: （1）（计算临届水深、临界底坡）判断两矩形断面渠道是急流还是缓流，确定是否为水跃衔接。（答案：是） （2）计算（或查附录C）求正常水深，把视为跃前水深，求跃后水深与比较。 答案：远驱式水跃第8章一、 选择题 1实用断面堰常常设计成真空堰，其目的是（ B ）（a）减小水流对坝面的冲刷 （b）提高过流能力（c）减小空化空蚀 （d）节省建筑材料2、小桥过流与（ C ）具有相同的水力特征。（a）薄壁堰流 （b）宽顶堰流 （c）实用断面堰流 （d）闸孔出流3. 宽顶堰形成淹没出流的充分条件是 ( D ) (a) (b)

7、(c) (d) 4下述堰的分类哪个正确（ A ）(a)/H 0.67 薄壁堰 (b) 0.67/H 10.0 宽顶堰(c) 0.67/H 2.5 薄壁堰二、 判断题1、 只要宽顶堰下游水深超过堰顶，就为淹没出流。（ 正确 ）2、 小桥过流的淹没出流条件与宽顶堰的淹没出流条件不同。（正确）3、 对于闸孔出流，当闸门开度与上游水深之比时，闸孔出流转化为堰流。（正确 ）4、对于薄壁堰，在堰宽b、堰高P和堰上水头H相同的情况下，完全堰的过流能力比侧收堰的过流能力大。（正确 ）三、 简答题1. 简述堰的三种类型及其共同的水力特征。 答: 堰分为三种类型: (1) 薄壁堰-判别标准 (2) 实用断面堰-判

8、别标准 (3) 宽顶堰-判别标准 共同的水力特征为上游水位壅高过堰时水面跌落。2. 堰流基本公式中，等系数与哪些因素有关。 答: 流量系数与行近流速的大小、表面张力有关。 侧收缩系数与堰宽与渠宽的比值（）有关。3. 宽顶堰淹没出流形成的充分必要条件是什么？ 答: 必要条件,充要条件是0.8H0。四、 计算题1、 一圆角进口无侧收缩宽顶堰，堰高P1=2.5m，P2=2.0m，堰上水头为0.40m，通过的流量为4m3/s，求宽顶堰的宽度。在不产生淹没出流的情况下，下游水深最大为多少？解:（1） 通过计算（）的值，选取流量系数公式，计算流量系数。 （2）求宽顶堰的宽度： （3）不产生淹没出流，下游水

9、深。2、 有一河道，用碎石单层铺砌加固河床，通过的流量m3/s，允许流速m/s，桥下游水深m， 若，允许桥前壅水深度m。 设计小桥孔径。解: （1）求桥下临界水深，判别是自由出流，还是淹没出流。（自由出流） （2）计算桥孔初始值: 取 (B =6.0m ) （3）复算求桥下临界水深，判别是自由出流，还是淹没出流。（仍为自由出流） （4）计算桥前壅水深度 H =1.81m 3m，假设各井抽水量相同，求总的抽水量。 解: 此题为井群的水力计算，可直接用公式求解。 答案:0.0984 m3/s。第10章一、选择题 1.重力相似模型中, 流速比尺等于几何比尺的( C )次方 。 A. 2 B. 1.5

10、 C. 1 D. 0.52. 重力相似模型中, 流量比尺等于几何比尺的( A )次方 。A. 2.5 B. 2 C. 1.5 D. 13. 重力相似模型中, 时间比尺等于几何比尺的( D )次方 。A. 2 B. 1.5 C. 1 D. 0.5二、判断题1. 凡是正确反映客观规律的物理方程式，必然是一个齐次量纲式。（正确 ）2. 力学相似的必要条件是几何相似，运动相似，动力相似。（ 正确 ）三、简答题1. 为什么在阻力平方区，雷诺准则自动满足？答: 从理论上讲，如同沿程损失一样，在阻力平方区，沿程阻力系数与雷诺数无关，当雷诺数充分大时，粘性可忽略不计，所以，在阻力平方区，雷诺准则自动满足。2.

11、 简述弗劳德准数的物理意义。 答: 弗劳德准数为常数，是指原型的弗劳德准数与模型的弗劳德准数相等，原型与模型量液流相似。四、计算题1. 有一单孔WES剖面混凝土溢流坝，已知坝高，坝上设计水头,流量系数，溢流孔净宽，在长度比尺的模型上进行试验，要求计算：（1）设计模型流量； （2）如在模型坝趾测的收缩断面表面流速,计算原型相应流速 解：首先计算原型流量、流量比尺、速度比尺。按原型与模型换算关系计算。答案：流量 流速Winger Tuivasa-Sheck, who scored two tries in the Kiwis 20-18 semi-final win over England, h

12、as been passed fit after a lower-leg injury, while Slater has been named at full-back but is still recovering from a knee injury aggravated against USA.Both sides boast 100% records heading into the encounter but Australia have not conceded a try since Josh Charnleys effort in their first pool match

13、 against England on the opening day.Aussie winger Jarryd Hayne is the competitions top try scorer with nine, closely followed by Tuivasa-Sheck with eight.But it is recently named Rugby League International Federation player of the year Sonny Bill Williams who has attracted the most interest in the t

14、ournament so far.The Kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the World Cup in both rugby league and rugby union after triumphing with the All Blacks in 2011.Id give every award back in a heartbeat just to get across the line this weekend, said W

15、illiams.The (lack of) air up there Watch mCayman Islands-based Webb, the head of Fifas anti-racism taskforce, is in London for the Football Associations 150th anniversary celebrations and will attend Citys Premier League match at Chelsea on Sunday.I am going to be at the match tomorrow and I have as

16、ked to meet Yaya Toure, he told BBC Sport.For me its about how he felt and I would like to speak to him first to find out what his experience was.Uefa hasopened disciplinary proceedings against CSKAfor the racist behaviour of their fans duringCitys 2-1 win.Michel Platini, president of European footb

17、alls governing body, has also ordered an immediate investigation into the referees actions.CSKA said they were surprised and disappointed by Toures complaint. In a statement the Russian side added: We found no racist insults from fans of CSKA. Baumgartner the disappointing news: Mission aborted.The

18、supersonic descent could happen as early as Sunda.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the

19、 lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he cr

20、osses the boundary layer (called the tropopause),e can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet ( Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.They blew it in 2008 when they got caught cold in

21、the final and they will not make the same mistake against the Kiwis in Manchester.Five years ago they cruised through to the final and so far history has repeated itself here - the last try they conceded was scored by Englands Josh Charnley in the opening game of the tournament.That could be classed

22、 as a weakness, a team under-cooked - but I have been impressed by the Kangaroos focus in their games since then.They have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick-chase. Theyve bee

23、n great at all the unglamorous stuff that often goes unnoticed in the stands but not by your team-mates.It is as though their entire tournament has been preparation for the final.In Johnathan Thurston, Cooper Cronk, Cameron Smith and either Billy Slater or Greg Inglis at full-back they have a spine

24、that is unmatched in rugby league. They have played in so many high-pressure games - a priceless asset going into Saturday.The Kiwis are a lot less experienced but winning a dramatic match like their semi-final against England will do wonders for their confidence.They defeated Australia in the Four Nations final in 2010 and the last World Cup, and know they can rise to the big occasion.9