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工程流体力学孔珑第三版答案

【篇一：流体力学课后习题答案自己整理孔珑4版】

txt>孔珑第四版

第2章流体及其物理性

质 ............................................................................................................... 4 2-1 ............................................................................................................................................. 4 2-3 ............................................................................................................................................. 4 2-4 ............................................................................................................................................. 6 2-5 ............................................................................................................................................. 6 2-6 ............................................................................................................................................. 6 2-7 ............................................................................................................................................. 7 2-8 ............................................................................................................................................. 7 2-9 ............................................................................................................................................. 8 2-11 ........................................................................................................................................... 8 2-12 ........................................................................................................................................... 9 2-13 ........................................................................................................................................... 9 2-14 ......................................................................................................................................... 10 2-15 ......................................................................................................................................... 10 2-16 ......................................................................................................................................... 11 第3章 流体静力

学 ....................................................................................................................... 12

3-1 ........................................................................................................................................... 12 3-2 ........................................................................................................................................... 12 3-3 ........................................................................................................................................... 13 3-5 ........................................................................................................................................... 13 3-6 ........................................................................................................................................... 14 3-9 ........................................................................................................................................... 14 3-10 ......................................................................................................................................... 15 3-21 ......................................................................................................................................... 18 3-22 ......................................................................................................................................... 19 3-23......................................................................................................................................... 20 3-25 ......................................................................................................................................... 20 3-27 ......................................................................................................................................... 20 第4章 流体运动学及动力学基

础 .............................................................................................. 22 4-2 ........................................................................................................................................... 22 4-5 ........................................................................................................................................... 22 4-6 ........................................................................................................................................... 23 4-8 ........................................................................................................................................... 23 4-11 ......................................................................................................................................... 24 4-12 ......................................................................................................................................... 24 4-14 ......................................................................................................................................... 25 4-

22 ......................................................................................................................................... 25 4-24 ......................................................................................................................................... 26 4-26 ......................................................................................................................................... 27 第6章作

业..................................................................................................................................... 28 6-1 ........................................................................................................................................... 28 6-3 ........................................................................................................................................... 28 6-7 ........................................................................................................................................... 29 6-10 ......................................................................................................................................... 29 6-11 ......................................................................................................................................... 29 6-12 ......................................................................................................................................... 30 6-17 ......................................................................................................................................... 31 第2章流体及其物理性质 2-1

????i?i?1.341kg/m3 2-3

则根据理想气体状态方程，可知 p1p?2 ?1t1?2t2

2）运动粘度，与课本14页例题2-4题比较

先求出每一种气体在170℃时的动力粘度，利用苏士兰公式，课本12页。

利用公式2-19求出混合气体在工况下的动力黏度： 6

?24.83?10-（ pa?s）

工作状态下的运动粘度?? ?24.83

??10?6?30.62?10?6m2/s ?0.8109

【篇二：工程流体力学(孔珑版)第三章_题解print】

图3-35 习题3-2示意图

【解】 p1ga?p2gas??hogh2?p2air s?hogh1?p1a ir22 ?p2ai rp1gas??gasgh?p2gas p1ai?r?aighr ?hogh1?p1air??gasgh?p2gas 2 p2gas?p1air??h2ogh2??airgh

?hogh1??gasgh??hogh2??airgh 22 ?hoh1??hoh2??airh??gash 22

?gas??hh1?h20.1?0.115???1000??1.28?0.53kg/m3 air2oh20?? 图3-43 习题3-10示意图

【解】 p1??hog?h?h1??pp1??hgg?h2?h1??p2 2 p3??h2og?h2?h3??p2p3??hgg?h4?h3??pa ?hog?h?h1??p??hgg?h2?h1??p2 2 ?hog?h2?h3??p2??hgg?h4?h3??pa 2

?hog?h?h1?h2?h3??p??hgg?h2?h1?h4?h3??pa 2 p??hgg?h4?h3?h2?h1???h2og?h?h1?h2?h3??pa

?13600?9.807??2.3?1.2?2.5?1.4??1000?9.807??3?1.4?2.5?1.2??101325

?366310.14?pa?

p??hgg?h4?h3?h2?h1???h2og?h?h1?h2?h3??pa

?13600?9.80665??2.3?1.2?2.5?1.4??1000?9.80665??3?1.4?2.5?1.2??101325

?pa??366300.683

【3-12】【解】两支管中的液面高度差为： ?h?l?tan??al?25.5 mm （ans.） g

【3-15】 图3-48所示为一等加速向下运动的盛水容器，水深h=2m，加速度a=4.9m/s2。试确定：（1）容器底部的流体绝对静压强；（2）加速度为何值时容器底部所受压强为大气压强？（3）加速度为何值时容器底部的绝对静压强等于零？ 图3-48 习题3-15示意图

【解】 fx?0，fy?0，fz?a?g

压强差公式 dp???fxdx?fydy?fzdz? dp???fxdx?fydy?fzdz????a?g?dz ?p

padp????a?g?dz 0?h

?a?p?pa???a?g???h????a?g?0??h?g?a???gh??1?g?? ?? ?a?p?pa??gh??1?g?? ??

p?pa??h?g?a?a?g?p?pa ?h （1）

p?pa??h?g?a??101325?1000?2??9.80665?4.9??111138.3?pa? （2） a?g? （3）

a?g?p?pap?pa?g?a?g?9.8066ms2 ?h?h??p?pa0?101325?9.80665??60.469s25 ?h1000?2??

【3-16】 图3-49所示为一圆柱形容器，直径d=300mm，高

h=500mm，容器内装水，水深h1=300mm，使容器绕铅直轴作等角速旋转。（1）试确定水正好不溢出时的转速n1；（2）求刚好露出容器底面时的转速n2；这时容器停止旋转，水静止后的深度h2等于多少？

图3-49 习题3-16示意图

【解】 初始状态圆筒中没有水的那部分空间体积的大小为 1v??d2?h?h1? (1) 4

圆筒以转速n1旋转后，将形成如图所示的旋转抛物面的等压面。令h为抛物面顶点到容器边缘的高度。空体积旋转后形成的旋转抛物体的体积等于具有相同底面等高的圆柱体的体积的一半 v?112??dh (2) 24 由(1)(2)，得

1211?d?h?h1????d2h (3) 424 即

h?2?h?h1? (4)

等角速度旋转容器中液体相对平衡时等压面的方程为 ?2r2

2?gz?c (5)

d，z?h，2对于自由液面，c=0。圆筒以转速n1旋转时，自由液面上，边缘处，r? 则

?d??2???2??gh?0 (6) 22 得

??22gh (7) d 由于 ??2?

n1?30??n1 (8) 60?3022gh602gh (9) ???d?d

（1）水正好不溢出时，由式(4)(9)，得 2g?2h?h1gh?h1 (10) n1???d?d

即 n1?120?.80665?0.5?0.3?rmin? ?178.3??0.3 （2）求刚好露出容器底面时，h=h，则

n1?2gh2gh60?2?9.80665?0.5?rmin? ???199.4?d?d??0.3 （3）旋转时，旋转抛物体的体积等于圆柱形容器体积的一半 v?112??dh (11) 24

这时容器停止旋转，水静止后的深度h2，无水部分的体积为 1v??d2?h?h2? (12) 4 由(11)(12)，得

1121??dh??d2?h?h2? (13) 244 得

h2?h0.5??0.25?m? 22

【篇三：工程流体力学_第四版_孔珑_作业答案_详解】

2-3.上题中烟气的实测温度t=170℃，实测静计压强pe=1432pa，当地大气压强pa=10058pa。试求工作状态下烟气的密度和运动粘度。 2-4.当压强增量为50000pa时，某种液体的密度增长0.02%，试求该液体的体积模量。

2-12.一平板距离另一固定平板0.5mm,两板间充满液体，上板在每平方米上有2n的力作用下以0.25m/s的速度移动，试求该液体的粘度。 2-14. 一重500n的飞轮的回转半径为30cm，由于轴套间流体粘度的影响，当飞轮600r/min旋转时，它的角减速度为0.02rad/s2。已知轴套的长度为5cm，轴的直径为2cm以及他们之间的间隙为0.05mm。试求流体的粘度。

2-15. 直径为5.00cm的活塞在直径为5.01cm的缸体内运动。当润滑油的温度由0℃升高到120℃时，求推动活塞所需的力减少的百分数。用图1-5中相对密度d=0.855的原油的粘度进行计算。