电大流体力学形成性考核册(答案1)

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1、专业好文档作业1答案 (第1章、第2章)第1章一、选择题1、牛顿内摩擦定律适用于 （ B ）A、任何流体 B、牛顿流体 C、非牛顿流体2、液体不具有的性质是 （ C ）A、易流动性 B、压缩性 C、抗拉性 D、粘滞性3、连续介质假定认为流体（ C ）连续。A、在宏观上 B、在微观上 C、分子间 D、原子间4、在国际制单位制中流体力学基本量纲不包括 （ D ）A、时间 B、质量 C、长度 D、力5、在静水中取一六面体，作用在该六面体上的力有 ( D )A、切向力、正压力 B、正压力、重力 C、正压力、重力 D、正压力、切向力、重力6、下属那些力属于质量力 （E ）A、惯性力 B、粘滞力 C、弹性

2、力 D、表面张力 E、重力二、判断题1、压强和切应力属表面力。 （正确）2、流体惯性力与加速度方向相同。 （错误）3、粘滞性可以制止流体流动。 （正确）4、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。 （正确）三、简答题（要点）1. 为什么要建立连续介质模型？答：液体（气体）是由分子组成的，分子间有空隙，不连续。工程上研究的流体，关心的是流体宏观的物理性质。把流体看成为由质点组成的连续体连续介质模型，目的是建立描述流体运动的连续函数，便于应用数学工具，解决工程实际问题。2什么是流体的粘滞性？它对流体流动起什么作用？答：流体具有的阻滞变形运动的特性流体的粘滞性，它对流体流动产生阻力，造

3、成能量损失。3动力粘滞系数和运动粘滞系数有什么区别？答：两者都反映流体的粘滞性，为动力量，为运动量，量纲不同。4. 容器内盛有液体，求下述不同情况时该液体所受单位质量力？（1） 容器静止时； 液体所受单位质量力仅有重力。（2）容器以等加速度g垂直向上运动 ：液体所受单位质量力为2g。（3）容器以等加速度g垂直向下运动。液体所受单位质量力为0。5. 试分析图中三种情况下水体A受哪些表面力和质量力？（1）静止水池；（2）顺直渠道水流（均匀流）；（3）平面弯道水流。（1）：水体A受哪些表面力为压应力（正压力），质量力为重力g。（2）：水体A受哪些表面力为压应力和切应力，质量力为重力g（均匀流）。（3

4、）：水体A受哪些表面力为压应力和切应力，质量力为重力g和惯性力。 一、 作图题（略）二、 计算题 (解题思路与答案)1. 已知某水流流速分布为，u的单位为m/s ，y为距壁面的距离，单位为m。（1）求y=0.1、0.5、1.0m处的流速梯度；（2）若水的运动粘滞系数，计算相应的切应力。解：（1）： 求出点流速,设的增量=0.01m 处的点流速，求出求解流速梯 0. 5477 , 0.1332 ,0.07169 (2) ：5.53 ; 1.345; 0.724。2.已知温度20时水的密度，动力粘滞系数，求其运动粘滞系数？解：直接用公式解，注意单位制。 ：1.0038第2章一、选择题(略)1、某点

5、存在真空时， （A）（D）A、该点的绝对压强为正值 B、该点的相对压强为正值C、该点的绝对压强为负值 D、该点的相对压强为负值2、流体静压强的（B）A、方向与受压面有关 B、大小与受压面积有关 C、大小与受压面积方位无关 3、流体静压强的全微分式为（C）A、dp=p(Xdx + Ydy + Zdz) B、p=p(x，y，z) C、4、压强单位为N/m2时，采用了哪种表示法 （ A ）A、应力单位 B、大气压倍数 C、液柱高度5、密封容器内液面压强小于大气压强，其任一点的测压管液面 （ A ）A、高于容器内液面 B、低于容器内液面 C、等于容器内液面二、判断题1、等压面与质量力垂直。 （ 错误

6、）2、某点存在真空，是指该点的压强小于大气压强 （ 错误 ）3、静止流体中某点压强的大小，不仅与其淹没深度有关还与受压面的方位有关。 （正确）4、相对压强的数值可为正值，也可以是负值。 （ 错误 ）5、静止液面下的闸板的总压力作用中心与闸板形心重合。 （正确）6、和大气相通容器的测压管液面一定与容器内液面高度相同。 （正确）7、相对静止的液体的等压面一定是水平面。 （正确）三、简答题1.等压面是水平面的条件是什么？:连续介质 同一介质 单一重力作用下.2. 同一容器中装两种液体，且，在容器侧壁装了两根测压管。试问：图中所标明的测压管中液面位置对吗？为什么？ ：不对，（右测压管液面要低一些，从点

7、压强的大小分析）3. 图中三种不同情况，试问：A-A、B-B、C-C、D-D中哪个是等压面？哪个不是等压面？为什么？ ：（ a）A-A是 （b）B-B不是 （c）C-C 不是， D-D是。四、作图题(略)五、计算题(解题思路与答案)1. 已知某点绝对压强为80kN/m2，当地大气压强pa=98kN/m2。试将该点绝对压强、相对压强和真空压强用水柱及水银柱表示。解： 用水柱高表示（1）该点绝对压强：8.16mH2o （2）该点相对压强：-1.84mH2o（3）该点真空压强：1.84mH2o 用水银柱高表示（1）该点绝对压强：599.1mm Hg （2）该点相对压强：-135.4 mm Hg （3

8、）该点真空压强：135.4 mm Hg2. 一封闭水箱自由表面上气体压强p0=25kN/m2，h1=5m，h22m。求A、B两点的静水压强。解：由压强基本公式求解 = 7.551 mH2o (74 kN/m2) = 4.551 mH2o (44.6 kN/m2)3 如图所示为一复式水银测压计，已知，(改为3.5m)。试求水箱液面上的绝对压强？ 解： 找已知点压强(复式水银测压计管右上端) 找出等压面 计算点压强,逐步推求水箱液面上的压强. : =273.04 kN/m24 某压差计如图所示，已知HA=HB=1m，H=0.5m。求：。解：找出等压面 求出相对的点压强 列平衡方程式求AB点的压强差

9、. 空气的不计. =47 kN/m2 (4.8 mH2o)5. 水闸两侧都受水的作用，左侧水深3m、右侧水深2m。试求作用在单位宽度闸门上静水总压力的大小及作用点位置（用图解法和解析法分别求解）。解：画出相对压强分布图, 计算各侧静水压力, 求静水总压力的大小 列力矩平衡方程求静水总压力的作用点位置。 P=24.5 1.267m(作用点到底部的距离)6. 一弧形闸门AB，宽b=4m，圆心角45，半径r=2m，闸门转轴恰与水面齐平。求作用于闸门的静水压力及作用点（改为：作用力的方向）。解：画出压力体图, 计算水平方向分力、铅垂方向分力, 求出合力及作用力的方向 92.59 Winger Tuiv

10、asa-Sheck, who scored two tries in the Kiwis 20-18 semi-final win over England, has 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 Austra

11、lia have not conceded a try since Josh Charnleys effort in their first pool match 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 pl

12、ayer of the year Sonny Bill Williams who has attracted the most interest in the tournament 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

13、 every award back in a heartbeat just to get across the line this weekend, said Williams.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 Leagu

14、e match at Chelsea on Sunday.I am going to be at the match tomorrow and I have asked 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 behavi

15、our of their fans duringCitys 2-1 win.Michel Platini, president of European footballs 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 in

16、sults from fans of CSKA. Baumgartner the disappointing news: Mission aborted.The 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 a

17、nd limited cloud cover. The balloon, with capsule attached, will move through the 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 com

18、mercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses 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 resembl

19、ing an Olympic diving platform.They blew it in 2008 when they got caught cold in 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 E

20、nglands Josh Charnley in the opening game of the tournament.That could be classed 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, esp

21、ecially on their own goal-line, completing sets and a good kick-chase. Theyve been 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, Cam

22、eron Smith and either Billy Slater or Greg Inglis at full-back they have a spine 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.8