工程流體力學(xué)基礎(chǔ)作業(yè)答案

1、z tan dzcostan3 Hz3dz工程流體力學(xué)基礎(chǔ)作業(yè)1-9已知椎體高為H,錐頂角為2,錐體與錐腔之間的間隙為，間隙內(nèi)潤滑油的動力黏度為，錐體在錐腔內(nèi)以的角速度旋轉(zhuǎn)，試求旋轉(zhuǎn)所需力矩M的表達(dá)式。解：以錐頂為原點(diǎn)，建立向上的坐標(biāo)zvvrztan_2H2r,dz0cos_22H2ztancos.34tanHcos41-10已知動力潤滑軸承內(nèi)軸的直徑D 0.2m,軸承寬度b 0.3m,間隙0.8mm,間隙內(nèi)潤滑油的動力黏度0.245Pal - s,消耗白功率 P 50.7kW,試求軸的轉(zhuǎn)速n為多少?解：力矩T * AD2一一一 3? Db?D 旦224角速度P c 41P 3T D3b轉(zhuǎn)速n

2、6026,PD3b2830r/min可編輯2-10如果兩容器的壓強(qiáng)差很大，超過一個(gè)U形管的測壓計(jì)的量程，此時(shí)可以將兩個(gè)或兩個(gè)以上的U形管串聯(lián)起來進(jìn)行測量。若已知660cm,h251cm,油的密度i830kg/m3,水銀的密度213600kg/m3。試求A、B兩點(diǎn)的壓強(qiáng)差為多少?解：PiPaighAP2Pi2ghiP3P2ighcP4P32gh2PBP4ighBh2PbPahAhBhiheighA2ghiighe2gh2ighBh2PaPbighBh2hAhe2ghih22ghih2ighih22ighih2i39.006kPa2-22矩形閘門AB可繞其頂端A點(diǎn)旋轉(zhuǎn)，由固定在G點(diǎn)的重物控制閘門的

3、開閉。已知閘門寬120cm,長90cm,閘門和重物共重10000N,重心在G點(diǎn)處,G和A點(diǎn)的水平距離為30cm,閘門和水平面的夾角60。試確定水深多少時(shí)閘門正好打開？解：力矩T100000.33000Nm.33bh1.20.94慣性矩Icx0.0729m41212面積Abh1.08m2yDycIcxycAh.yDyc-gycsmat2hgIcxSin-gycsinATTgIcxsin2Tyc-cx-Icx0.5768314mhhAgsin-gsinAhHyc-sin0.88926m2-31汽油箱底部有一錐形閥，D100mm,d50mm,d125mm,a100mm,b50mm,汽油密度為830k

4、g/m3,若略去閥芯的自重和運(yùn)動時(shí)的摩擦力不計(jì)，試確定：(1)當(dāng)測壓表讀數(shù)pe9806Pa時(shí)，提起閥芯所需的最小的力F;(2) F0時(shí)的計(jì)示壓強(qiáng)Pe解：(1)相當(dāng)自由液面高Hb-pe1.254739mg上面壓力體V上一D2d12H9.2387785103m3422V下a D2 d2 Dd12下面壓力體-d2a-D2d2H7.6528222103m344FV上V下g12.909NaD2d2Dd-d2a-D2d2H-D2d12H124441_22_2_22_22-aD2d2Ddd2aD2d2HD2d1H3aD22d2Dd3d2d120.17777778mPegHb1040Pa3-4已知流場中速度分

5、布為Vxyzt,vyxzt,vzxy。問:(1)該流動是否定常流動?(2)求t0時(shí)點(diǎn)(1,1,1)上流體微團(tuán)的加速度。解：(1)非定常axvxt103vxvx一xztayvytVxvyxazvxvyy2xyvyyzvyy2xyvxvz-zvyvzzvztvzvx一xyztyvyxzvzytxvzvz一z03-13噴管直徑D0.5m,收縮段長l0.4m,30,若進(jìn)口平均速度vi0.3m/s,求出口速度V2。解：dD2ltan0.03812m2DV2Vi51.613md3-14圖示文杜里管和壓強(qiáng)計(jì)，試推導(dǎo)體積流量和壓強(qiáng)計(jì)讀數(shù)之間的關(guān)系式解：由連續(xù)方程Vidi2v2d2222伯努利方程ZiB人Z2&

6、區(qū)g2gg2gPi P2ZiZ2g2V224d2di等壓關(guān)系 Pighi P2gh2mgH高度關(guān)系Zihi Z2 h2 HPi P2 g h2himgHg Zi z2 H mgHg Zi Z2m gH42d2V2 i m gH2diV2gH4d2diqVd242 m gH41生d13-25直立圓管直徑10mm,端裝有5mm的噴管，噴管中心到1截面的距離為3.6m,從噴管出口排入大氣的水流出口速度為18m/s,不計(jì)摩擦損失，計(jì)算截面1處的計(jì)示壓強(qiáng)。解：d1 10 mmd25mm3v218 m/s , H 3.6 m,1000 kg/m由連續(xù)方程Vld 2V2 一d14.5 m/s由伯努利方程2g

7、2 v22gPi2萬v22v1一51.871 8 1 05 Pa3-33消防水槍水平工作，水槍進(jìn)口直徑di15mm,出口直徑do7mm,水槍工作水量qv160L/min,試確定水槍對消防隊(duì)員的后坐力解：qv2.66667103m3/sAd121.767146104m24A-do20.3848451104m24qvv1-15.0902m/sAv0%69.2919m/sA022由伯努利方程0反幺00v-g2g2gp1-v02v122.286830106Pa2由動量方程 FP1A1P0A02 A2 AV0 A0V1 A12 2AAFv0APoAoViAP1A1噴管對水的作用力184.77827444

8、.35666259.57839N水對噴管的作用力為F259.57839N,方向向右。考慮管內(nèi)靜壓對后端的作用力，合力為Fp1A144.53786N,方向向左。5-1用管徑d200mm的圓管輸送石油，質(zhì)量流量qm90000kg/h,密度900kg/m3,石油冬季時(shí)的運(yùn)動黏度為16104m2/s；在夏季時(shí)，24105m2/s,試求冬、夏季石油流動的流態(tài)。解：速度vqm0.884194m/sd24vdRqvd294.73層流1Re2vd4420.97湍流25-5輸油管的直徑d150mm,長L5000m,出口端比進(jìn)口端高h(yuǎn)10m,輸送油的質(zhì)量流量qm15489kg/h,油的密度859.4kg/m3,進(jìn)

9、口端的油壓Pei49104Pa,沿程損失系數(shù)0.03,求出口端的油壓p“。解：面積Ad20.01767146m24平均速度vqm0.283304m/sA.2沿程損失hf-4.092188md2g伯努利方程取h衛(wèi)也hfggPeoPeihhfg3.7123105Pa5-9內(nèi)徑為6mm的細(xì)管，連接封閉容器A及開口容器B,容器中有液體，其密度為997kg/m3,動力黏度0.0008Pas,容器A上部空氣計(jì)示壓強(qiáng)為Pa34.5kPa。不計(jì)進(jìn)口及彎頭損失。試問液體流向及流量qv。解：勢能水頭hA曳14.528607mghB1.41.4sin452.3899495m故A-B假設(shè)為層流,414!哈根-泊肅葉公

10、式qVpABg5.938598104m3/s128l128l4q“檢驗(yàn)v721.0035m/sd2Revd157053.62320故不是層流按湍流光滑管計(jì)算0.3164-0.25RehAhB0.3164 l v2C 0.25 1Re d 2g0.3164 l v20.25vdd 2g0.25:hAhBdv2g2.5887843m/s0.3164lqVd2v7.319615105m3/s45-11在管徑d100mm、管長 L300m的圓管中流動著t 10 c的水，其雷諾數(shù)Re 8 104o試求當(dāng)管內(nèi)壁為0.15mm的均勻沙粒的人工粗糙管時(shí),其沿程能量損失。解：d/666.66726.98 d/

11、87 45537 Re2308 d / 0.85 580174故在湍流粗糙管過渡區(qū)1.4220.023783dlgRe一黏度1.308103Pas平均速度vRe1.0464m/s沿程損失hf Ld 2g3.9832 mH2O5-28在分支管道系統(tǒng)中，已知Li1000m,di1m,10.0002m,zi5m；L2600m,d20.5m,20.0001m,z230m；L3800m,d30.6m,3 0.0005m,Z325m；1106m2/s。水泵的特性數(shù)據(jù)為，當(dāng)流量qv為0、1m3/s、2m3/s、3m3/s時(shí)，對應(yīng)的壓頭Hp為42m、40m、35m、25m,試求分支管道中的流量qv1、qv2、

12、3。解：相對粗糙度1/d10.0002,2/d20.0002,3/d30.00083。擬合水泵特性曲線Hp42qvqV2-qv3p6232水泵吸入端靜水頭hsZ1幺2g水泵壓出端靜水頭hphsHp設(shè)節(jié)點(diǎn)靜壓頭hj2節(jié)點(diǎn)總壓頭hjThj2g各段壓頭損失hf1hphjhf2hjTz2hf3hjTZ3Lv28Lqv2fd而2gd5vdRe查入檢驗(yàn)節(jié)點(diǎn)處的連續(xù)性。試取水泵流量qV11.5m3/sqvi1.51.561.59Vi1.909861.986252.02445hs4.8144.7994.871Hp3837.69837.541hp42.81442.49742.412Re1.90986E61.98

13、625E62.02445E6入0.01420.01420.0142hf12.6412.8562.967hj40.17339.64139.445hjT40.35939.84239.654hf210.3599.8429.654b0.0150.01430.01430.0143V23.35968Re21.67984E6qv20.675620.658550.65223hf315.35914.84214.6540.0190.01920.01920.0192V33.44834Re2.06901E6qv30.969910.953440.94738qv2+qv31.6461.6121.6005-29由兩個(gè)環(huán)路組

14、成的簡單管網(wǎng)，已知L11000m,d10.5m,i0.00005m；L21000m,d20.4m,20.00004m；L3100m,d30.4m,0.00005m； L5 1000 m, d50.3m,30.00004m；L41000m,d40.5m,40.000042m；管網(wǎng)進(jìn)口A和出口B處水的流量為1m3/s。忽略局部損失，并假定全部流動處于湍流粗糙區(qū)，試求經(jīng)各管道的流量。解：相對粗糙度i/di2/d23/d34/d40.0001,5/d50.00014。沿程損失系數(shù)12340.012,50.013。試取流量值，且滿足qV1qV21m3/sqv1qv3qv4qV2qV3qV5計(jì)算各管道損失

15、hf$qv2qv2gd其中131.74,296.86,39.69,431.74,5442.2。檢驗(yàn)每個(gè)環(huán)路是否滿足hf1hf2hf3hf5hf4hf3不滿足則修正流量。qvi0.60.650.64qv20.40.350.36qv30.10.150.15qv40.70.80.79qv50.30.20.21hfi11.42613.41013.001hf215.49811.86512.553hf30.0970.2180.218hf415.55320.31419.809hf539.79817.68819.5016-3空氣產(chǎn)1.4,R=287J/(kgK)在400K條件下以聲速流動,試確定：氣流速度。對

16、應(yīng)的滯止聲速。對應(yīng)的最大可能速度解：ccr,RT400.899m/sv400.899m/s439.163 m/svmax981.998m/s6-6空氣管流丫=1.4,R=287.43J/(kgK)在管道進(jìn)口處300K,Pi3.45105Pa,vi150m/s,Ai500cm2,在管道出口處T2277K,P22.058105Pa,V2260m/s,試求進(jìn)出口處氣流的各種狀態(tài)參數(shù)：T,p,何，Tcr,Pcr,fCr,A,Vmax。解：進(jìn)口處:c1,RT；347.4487m/sP1RT14.00097 kg/m3v1Ma10.4317184C1_12,T10T11Ma1311.183K2P10P1T

17、13.92 105 Pa104.3843kg/m3T1crT10-259.319K1215cP1crP101210Pa12-2T20 T2 1 Ma 2310.598 K31cr102.7788kg/m31LRic；323.033m/sciciV10.4643clcr791.266m/s出口處:c2RT2333.8643m/s意258484kg/m3A2-1V12A1446.498cm2v2Ma2v2c20.7787595P20P2T201T253.0723105Pa203.4414kg/m32T2crT20258.832K1P2cr2cr21P201.6230105Pa11213202.18

18、16kg/m31C2cr.RT2cr322.730m/sv20.8056c2crv2maxC2cr1790.524m/s16-11空氣氣流在收縮噴管截面1上的參數(shù)為Pi3v1150m/s,d146mm,在出口截面2上馬赫數(shù)為Ma105Pa,T1340K,1,試求出口的壓強(qiáng)、溫度和直徑。解:RT1369.6106m/sMa1v10.4058325TerPer2121Ma1292.6663K11T1P1上1.7752105PaT1derdiMa1PlRTierpcrRTerver1122-1Ma113.0744kg/m3.32.11345kg/meer,RTer342.9188m/sdiMa11Ter2-1T136.694mmdcrdi36.694mm9-1空氣穩(wěn)定地流過一等截面管，在某截面處，氣流的參數(shù)pi68930Pa,Ti670K,vi915m/s,求發(fā)生在狀態(tài)1處的正激波波后的壓強(qiáng)、溫度和速度,解：1.4R287J/(kg-K)c11RI518.851m/sv1Ma11.76351C12Ma121p2p11238611Pa111X-1008.02 K12 Ma1212T2T12111Ma1-221Ma1，v2v12397