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《工程流体力学》课后习题答案

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.......................................................................................................................................... 24 4-22.......................................................................................................................................... 25 4-24.......................................................................................................................................... 26 4-26.......................................................................................................................................... 27

第6章作业 ............................................................................................................................................ 28

6-1 ........................................................................................................................................... 28 6-3 ........................................................................................................................................... 29 6-7 ........................................................................................................................................... 29 6-10.......................................................................................................................................... 29

6-11 .......................................................................................................................................... 30 6-12.......................................................................................................................................... 31 6-17.......................................................................................................................................... 31

第2章流体及其物理性质

2-1

已知某种物质的密度ρ=2.94g/cm3，试求它的相对密度d。【2.94】 解：ρ=2.94g/cm3=2940kg/m3，相对密度d=2940/1000=2.94

2-2已知某厂1号炉水平烟道中烟气组分的百分数为，α(CO2)=13.5%α(SO2)=0.3%，α(O2)=5.2%，α(N2)=76%，α(H2O)=5%。试求烟气的密度。

解：查课表7页表2-1，可知ρ(CO2)=1.976kg/m3，ρ(SO2)=2.927kg/m3，ρ(O2)=1.429kg/m3，ρ(N2)=1.251kg/m3，ρ(H2O)=1.976kg/m3，ρ(CO2)=1.976kg/m3，

2-3

上题中烟气的实测温度t=170℃，实测静计示压强Pe=1432Pa，当地大气压Pa=100858Pa。试求工作状态下烟气的密度和运动粘度。 【0.8109kg/m3，2.869×10-5㎡∕s】 解：

1）设标准状态下为1状态，则p1=101325pa，T1=273K，ρ1=1.341kg/m3 工作状态下为2状态，则p2=pa-pe=100858-1432=99416pa，T2=273+170=443K，

则根据理想气体状态方程，可知

p1p?2 ?1T1?2T2带入数值，可得工作状态下ρ2=0.8109kg/m3 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。

黏度（标态下） 工作温度T（K) 二氧化碳 14.8 443 二氧化硫 11.6 443 氧气 19.2 443 氮气 17.6 443 水 8.93 443 S 254 306 125 104 961 黏度（工况下） 25.07427072 利用公式2-19求出混合气体在工况下的动力黏度：

分子量 0.135 0.003 0.052 0.76 0.005 44 64 32 28 18 分子量开平方 6.63 8.00 5.66 5.29 4.24 黏度 23.13 18.54 27.81 25.07 16.22 分子 20.71 0.44 8.18 100.82 0.34 130.50 工况动力黏度 分母 0.90 0.02 0.29 4.02 0.02 5.26 24.83 6pa?s）工作状态下的动力黏度为??24.83?10-（

工作状态下的运动粘度???24.83??10?6?30.62?10?6m2/s ?0.81092-4

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。

2-5

绝对压强为3.923×105Pa的空气的等温体积模量和等熵体积模量各等于多少？

2-6

充满石油的油槽内的压强为4.9033×105Pa,今由槽中排出石油40kg，使槽内压强降到9.8067×104Pa，设石油的体积模量K＝1.32×109Pa。