-.z.Chapter1Fluidstatics流體靜力學(xué)連續(xù)介質(zhì)假定(Continuumassumption)：Therealfluidisconsideredasno-gapcontinuousmedia,calledthebasicassumptionofcontinuityoffluid,orthecontinuumhypothesisoffluid.流體是由連續(xù)分布的流體質(zhì)點(diǎn)(fluidparticle)所組成，彼此間無間隙。它是流體力學(xué)中最根本的假定，1755年由歐拉提出。在連續(xù)性假設(shè)之下，表征流體狀態(tài)的宏觀物理量在空間和時(shí)間上都是連續(xù)分布的，都可以作為空間和時(shí)間的函數(shù)。流體質(zhì)點(diǎn)〔Fluidparticle〕:AfluidelementthatissmallenoughwithenoughmolestomakesurethatthemacroscopicmeandensityhasdefinitevalueisdefinedasaFluidParticle.宏觀上足夠小，微觀上足夠大。流體的粘性〔Viscosity〕:isaninternalpropertyofafluidthatoffersresistancetosheardeformation.Itdescribesafluid'sinternalresistancetoflowandmaybethoughtasameasureoffluidfriction.流體在運(yùn)動(dòng)狀態(tài)下抵抗剪切變形的性質(zhì)，稱為黏性或粘滯性。它表示流體的部流動(dòng)阻力，也可當(dāng)做一個(gè)流體摩擦力量。Theviscosityofagasincreaseswithtemperature,theviscosityofaliquiddecreaseswithtemperature.牛頓摩擦定律〔Newton’slawofviscosity〕：Thedynamicviscosity〔動(dòng)力黏度〕isalsocalledabsoluteviscosity〔絕對(duì)黏度〕.Thekinematicviscosity〔運(yùn)動(dòng)黏度〕istheratioofdynamicviscositytodensity.pressibility〔壓縮性〕：Asthetemperatureisconstant,themagnitudeofpressibilityise*pressedbycoefficientofvolumepressibility(體積壓縮系數(shù))к,arelativevariationrate〔相對(duì)變化率〕ofvolumeperunitpressure.Thebulkmodulusofelasticity(體積彈性模量)Eisthereciprocalofcoefficientofvolumepressibilityк.流體的膨脹性(e*pansibility;dilatability)：Thecoefficientofcubicale*pansion(體積熱膨脹系數(shù))αtistherelativevariationrateofvolumeperunittemperaturechange.外表力Surfacetension:Apropertyresultingfromtheattractiveforcesbetweenmolecules.-----單位長(zhǎng)度所受拉力外表力Surfaceforce——istheforcee*ertedonthecontactsurfacebythecontactedfluidorotherbody.Itsvalueisproportionaltocontactarea.作用在所研究流體外外表上與外表積大小成正比的力。Stress〔應(yīng)力〕isthesurfaceforceonperunitarea.質(zhì)量力Massforce——Theforceactingoneveryfluidmassparticlewithinthecontrolbody.Itsvalueisproportionaltoitsmass.Massforceisalsoknownasbodyforce.作用在流體的每一個(gè)流體質(zhì)點(diǎn)上，其大小與流體所具有的質(zhì)量成正比。EulerEquilibriumEquations歐拉平衡微分方程〔分量式〕1775年P(guān)hysicalMeaning:Forthefluidinequilibrium,surfaceforceponentspermassfluidareequaltomassforceponentspermassfluid.Pressurevariationrateina*esdirectionsareequaltomassforceponentsperunitvolumeina*esdirectionsrespectivelyconstant-pressureSurface(等壓面)——asurfacethatthepressureofeverypointinliquidisequal.monconstant-pressuresurfacesarefreeliquidsurfaceandinterfaceoftwounmi*edfluidsinequilibrium.平衡流體中壓強(qiáng)相等的點(diǎn)所組成的平面或曲面。PressureDistributionintheStaticFluid重力場(chǎng)中流體的平衡Conclusions:1.Pressureatapointinastaticfluidundergravityincreaseslinearlywithdepth.2.Pressureatapointinastaticfluidundergravityisequaltothesumofthepressureatthefreesurfaceandthefluidspecificweighttimingdepth.3.constant-pressuresurfaceinastaticfluidundergravityisahorizontalplane.4.E*tended:whilethepressureatapointandthedepthdifferencebetweentwopointsareknown,thepressureatanotherpointcanbecalculated.Absolutepressure(絕對(duì)壓力),Gagepressure(相對(duì)壓力,又稱“表壓力〞),andVacuum(真空度):表壓力＝絕對(duì)壓力－大氣壓力;真空度＝大氣壓力－絕對(duì)壓力FluidinRelativeEquilibrium(相對(duì)靜止流體)Equationofconstant-pressuresurface(等壓面方程):UniformLinearAcceleration等加速度直線運(yùn)動(dòng)流體:UniformRotationaboutaVerticalA*is等角速度旋轉(zhuǎn)流體:Chapter2basicequationsoffluidmechanics跡線pathline：thetraceafterasingleparticletravelsinafieldofflowoveraperiodoftime.流體質(zhì)點(diǎn)的運(yùn)動(dòng)軌跡曲線流線streamline：acurvethatshowthedirectionofanumberofparticlesatthesameinstantoftime.*一時(shí)刻處處與速度矢量相切的空間曲線--瞬時(shí)性。Stream-tube(流管)——Consideraclosedcurve(notstreamline)intheflowfield,thendrawstreamlinesthrougheverypointonit,soastoformatube-shapingspacewhosewallsarestreamlines.Thistubeiscalledthestream-tube.在流場(chǎng)中任取一個(gè)有流體從過的封閉曲線，在曲線上的每一個(gè)質(zhì)點(diǎn)都可以引出一條流線，這些流線簇圍成的管狀曲面稱為流管。Tube-flow流束——Fluidfullingthestreamtubeiscalledthetube-flowandthelimitofatube-flowisastreamline.流管的全部流體稱為流束。Ministream-tube微小流束——Thestreamtubewithaninfinitesimalsectionissaidtobemini-streamtube.Streamlineisthee*tremecaseofmini-streamtube.截面無窮小的流束。Totalflow總流——Totalofcountlessmini-streamtubesiscalledtotalflow.包含流動(dòng)中所有的微小流束。Crosssection(過水?dāng)嗝?---Thesectionisperpendiculartothedirectionoffluidflow.(suchaspipeflowandchannelflow)與流束或總流流線成正交的斷面。Discharge(流量)---Amountoffluidpassthroughacrosssectionperunittime(suchasthesectioninthechannelorpipe).單位時(shí)間通過*一過水?dāng)嗝娴牧黧w體積稱為體積流量，簡(jiǎn)稱流量。Meanvelocity斷面平均流速---Thevelocitiesofpointsonthesamecrosssectioninthetotalflowaredifferent,sousuallyanaveragevelocityisusedinsteadoftherealvelocityoverthecrosssection,thisaveragevelocityiscalledthemeanvelocity.Uniformflow均勻流：isdefinedasuniformflowwhenintheflowfieldthevelocityandotherhydrodynamicparametersdonotchangefrompointtopointatanyinstantoftime(inwhichthecrosssectionofeachstreamtuberemainsunchanged.流場(chǎng)中每一空間點(diǎn)的各運(yùn)動(dòng)參數(shù)〔速度，壓力〕不隨空間位置而變化。Nonuniformflow非均勻流：Flowsuchthatthevelocityvariesfromplacetoplaceatanyinstant.Steadyflow恒定流：theflowwhosemotionfactorsdon’tchangewithtime.流場(chǎng)中所有的運(yùn)動(dòng)要素不隨時(shí)間變化.Unsteadyflow非恒定流：theflowthatatleastoneofitsmotionfactorschangeswithtime.流場(chǎng)中至少有一個(gè)運(yùn)動(dòng)要素隨時(shí)間變化.Onedimensionalflow(一元流動(dòng))--allmainvariablesintheflowfieldcanbepletelyspecifiedbyasinglecoordinateifthevariationofflowparameterstransversetothemainstreamdirectioncanbeneglected.流動(dòng)參數(shù)只與一個(gè)坐標(biāo)變量有關(guān)。Twodimensionalflow(二元流動(dòng))-fluidmotionfactorsarefunctionoftwospacecoordinates.流動(dòng)參數(shù)與兩個(gè)坐標(biāo)變量有關(guān)。Three-dimensionalFlow(三元流動(dòng)):Fluidflow’smotionfactorsarefunctionsofthreespacecoordinates.流動(dòng)參數(shù)與三個(gè)坐標(biāo)變量有關(guān)。System〔系統(tǒng)〕——isasetofdefinitefluidparticlesselectedintheinterestofresearcher.由確定的流體質(zhì)點(diǎn)組成的流體團(tuán)或流體體積V(t)。系統(tǒng)邊界面S(t)在流體的運(yùn)動(dòng)過程中不斷發(fā)生變化。反映了拉格朗日觀點(diǎn)Controlvolume(控制體CV)——isdefinedasaninvariablyhollowvolumeorframefi*edinspaceormovingwithconstantvelocitythroughwhichthefluidflows.相對(duì)于坐標(biāo)系固定不變的空間體積V。是為了研究問題方便而取定的。反映了歐拉觀點(diǎn)ForaCV:1)itsshape,volumeanditscscannotchangewithtime.2)itisstationaryinthecoordinatesystem.(inthisbook)3)theremaybethee*changeofmassandenergyonthecs.Controlsurface控制面:thesurfaceareapletelyenclosestheCV.邊界面S稱為控制面。differentialformofcontinuityequation微分形式的連續(xù)性方程ForinpressiblefluidFor2-DinpressibleflowPhysicalmeaning:Thenetmassdischargeenteringthecontrolvolumeisequaltothemassincreasedinunittimeduetothechangeindensity.Fitfor:Steadyflow,unsteadyflow,pressibleandinpressiblefluid,idealfluidandrealfluid.Integralformofcontinuityequation積分形式的連續(xù)方程Physicalmeaning：在單位時(shí)間，由于控制體密度變化引起的質(zhì)量變化量〔增加量或減少量〕與通過控制體外表的質(zhì)量?jī)袅鞒隽俊擦鞒雠c流入的質(zhì)量差〕之和等于零。Steadyflow定常流動(dòng)inpressiblefluid不可壓縮流體MotionDifferentialEquation運(yùn)動(dòng)微分方程ForIDEALFLOWforViscousFlowBernoulliEquation伯努利方程〔1〕steadyflow定常流動(dòng)〔2〕inpressibleflow不可壓縮〔3〕integrationalongastreamline沿流線積分〔4〕massforceisapotentialforce質(zhì)量力有勢(shì)ForstreamlineForpressibleflowingravityfieldForpressibleflowwithfluidmachineryingravityfieldz(m)——theelevationheightabovedatumsurfaceo-o,calledtheelevationhead(位置水頭).p/(g)——risingheightoffluidwithunitweightundertheactionofpressureP,calledthepressurehead(壓力水頭).u2/(2g)——risingheightoffluidwithunitweightundertheactionofvelocityV,calledthevelocityhead(速度水頭),denotedashu——thelostmechanicalenergyfrom1to2pointsperunitweightfluid——Theeffectiveenergyobtainedaftertheunitweightoftheliquidflowsthroughthepump.單位重量液體流經(jīng)泵后獲得的有效能量。Headofdelivery揚(yáng)程Thesumofthemiscalledthetotalhead(總水頭),denotedasH.Pumppower泵功率：Fortheideal-fluidtotalflow理想流體總流的伯努利方程forthereal-fluidtotalflow實(shí)際流體總流的伯努利方程momentumintegralequation動(dòng)量積分方程ForCV——sumofthefluidmomentumchangeinCVandthenetoutflowmomentuminCS,isequaltotheresultantforce.Steadyflow：Moment-of-momentumintegralequation動(dòng)量矩積分方程Forsteadyflow：[流出動(dòng)量矩]CS–[流入動(dòng)量矩]CS=[合外力矩]CV+CSForcesonbend(彎頭〕fluidjetsondeflector(導(dǎo)流板〕Sprinkler(噴水器〕角速度：固定所需力矩Chapter3PipeFlowandBoundaryLayerTheory(管流和邊界層概述)Laminarflow(層流)：Inthefluidflowthefluidparticlesmovealongsmoothpathinlayerswithouttransversevelocityinthedirectionofmainflow,onelayerglidessmoothlyoveranadjacentlayer.Turbulentflow(紊流,湍流)orTurbulence：Ifthefluidparticleshaveatransversevelocitynormaltothemainflowdirection,thatleadstoparticlesmi*ingupeachother,withaviolenttransverseinterchangeofmomentum.Thisisturbulentflow(紊流,湍流)orturbulence.Reynoldsnumber雷諾數(shù)：isusedtodescribethecharacteristicofflow.Wettedperimeter(濕潤(rùn)長(zhǎng)度)：Thelengthofwallcontactedwithliquid.thehydraulicdiameter(水力直徑)DH:Thecharacteristicdimensionofnoncirculartube.HeadLoses〔能頭損失，或水頭損失)：thetotalenergylossesperunitweight〔單位重量流體所損失的機(jī)械能為能頭損失(水頭)〕,whichduetotheresistancebetweentwosectionsofgraduallyvariedflow.〔流體流動(dòng),克制粘性摩擦力,消耗機(jī)械能為熱能.〕FrictionLoss沿程水頭損失(hλ):Intheflowthroughastraighttubewithconstantcrosssection,theenergylossincreaseslinearlyinthedirectionofflowandthelossiscalledfrictionloss.(原因:粘性摩擦力,以及與管壁的摩擦阻力)Darcy-Weisbch(達(dá)西-韋斯巴赫)Equation:λ:thecoefficientoffrictionloss沿程阻力系數(shù),與流態(tài)和壁面有關(guān)Locallosses局部水頭損失(hξ)：Whentheshapeofflowpathchanges,suchassectionenlargementandsoon,itwillgiverisetoachangeinthedistributionofvelocityfortheflow.Thechangeresultsinenergyloss,whichiscalledminorlossorlocalloss.原因:流速急劇變化,流體質(zhì)點(diǎn)劇烈撞擊和摩擦.ζ：minorlosscoefficientorlocallosscoefficient為局部阻力系數(shù),與障礙物形式有關(guān)Headlosses總能量損失(hf=hλ+hξ)LAMINARFLOWTHROUGHCIRCULARTUBE圓管中的層流VelocitydistributionincrosssectionDischarge—Hagen-Poiseuille(哈根-泊肅葉)equation.Distributionofshearstress切應(yīng)力分布：壁面剪切力Headlossalongthepath沿程能量(阻力)損失pressuredrop壓強(qiáng)損失Headloss水頭損失：thecoefficientoffrictionloss：Powerloss(功率損失)：PulsationPhenomenon〔脈動(dòng)現(xiàn)象〕：Thephenomenonthatthephysicalparameterfluctuatesaroundacertainaveragevalueiscalledpulsationphenomenon〔脈動(dòng)現(xiàn)象〕.u=ū+u'where:ūistime-averagevelocity(時(shí)均速度);u'-theponentofrandomfluctuatingvelocity(脈動(dòng)速度).hydraulicsmooth(水力光滑):Ifviscoussublayermorethanabsoluteroughness(ie.>),theeffectofforthecoreofturbulentflowisverylittle,namely,theinfluenceofintheenergylossisverylittle.hydraulicrough(水力粗糙):Ifviscoussublayerlessthanabsoluteroughness(ie.<),thefluidparticleswithcertainvelocityimpactorcrashtheroughnessprojectionsofpipewall,sothevelocityoftheseparticleschangesradically.Itcauseseddy(渦流)orvorte*(漩渦)locally.Meantimetheinfluenceistransferredtothecoreofturbulentflow.Soplaysanimportantroleintheenergyloss.Parallellines并聯(lián)管路——Byafewsimplelinesortandemlinewhichinletsideandoutletpipingconnectedrespectively.Pipelineinseries/tandemlines(串聯(lián)管路〕：——Byacoupleofdifferentdiameterordifferentroughnesspipeline.BoundaryLayer邊界層:Thefluidparticlesonasolidboundarymustadhereto(粘著，附著)thesolidwallinspiteof(不管)theReynoldsnumberReintheflow.Thevelocityoffluidneartheboundaryvariesrapidlyinasteep(陡的)velocitygradient(速度梯度)outwardnormaltothewallwherethefluidhasazerovelocity.Thevelocitygradientsetsup(產(chǎn)生)shearforceneartheboundaryandforthisreasontheeffectofviscositycannotbeneglectedintheregion.ThisregioncalledBoundarylayer.ThelargertheReynoldsnumberis,thethinnertheboundarylayeris.Chapter4OrificeOutflowandgapflow(孔口出流與縫隙流動(dòng))Thin-walledorifice(薄壁孔口)：,theedgethicknessslightlyeffectsthejetflow,andonlyminorlosswasconsidered,thecontractedsectionlocatedatd/2afterthehole.Thick-walledorifice(厚壁孔口)：,alsonamedlongorifice(長(zhǎng)孔口)/nozzle(管嘴).Theedgethicknessdistinctlyeffectsthejetflow,andtheflowwasfirstcontractedandthendiffuseduntilcontactingthewall.Bothfrictionallossandminorlossshouldbeconsidered.bigorifice〔大孔口〕：H/d<=10，thehead,pressure,velocityonthesectionwillbechangedwiththeheight.smallorifice〔小孔口〕：H/d>10，thehead,pressure,velocityonthesectionwillNOTbechangedwiththeheight.free

outflow〔自由出流〕：thejetflowsintoatmospheredirectly,thepressureonthecontractedsectionwasBAR,pc=pa.submerged

outflow〔淹沒出流〕：thejetflowsdowntothewater.Contractedsection收縮斷面：thestreamlineswerecontractedafterthehole,andthesectionreachedtheminimumatd/2,whichwasthecontractedsectionC—C.contractioncoefficient收縮系數(shù)：theratiobetweenthecontractedsectionareaandtheholearea,labeledasCc:Thedischargecalculationofsteadyfreeflowinorifice孔口恒定自由出流流量計(jì)算Cvisthevelocitycoefficient流速系數(shù)dischargecoefficient流量系數(shù)gapflowbetweenstationary固定平板間的縫隙流動(dòng)velocitydistributiondischargeaveragevelocitypressurelossgapflowbetweenrelativelymovedparallelplates具有相對(duì)運(yùn)動(dòng)的兩平行平板間的流動(dòng)velocitydischarge壓差與平板運(yùn)動(dòng)方向一樣取正號(hào)；方向相反取負(fù)號(hào)gapflowbetweenconcentriccylinders同心圓環(huán)間的縫隙流動(dòng)dischargeChap.5SimilitudeandDimensionalAnalysis

相似理論和量綱分析ThethreesimilaritiesareessentialconditionsofDynamicSimilitudeofFluidMotion(流動(dòng)相似),inwhich,atanytime,alltheparametersofthemodelandprototypeareinthesameratiothroughouttheentireflowfield.DynamicSimilitudeofFluidMotion(流動(dòng)相似)includesGeometricsimilarity幾何相似,Kinematicsimilarity運(yùn)動(dòng)相似,andDynamicsimilarity動(dòng)力相似;Geometricsimilarity幾何相似isthebasicandthemostobviousrequirement;Kinematicsimilarity運(yùn)動(dòng)相似istheresult;Dynamicsimilarity動(dòng)力相似istheconditions.dynamicsimilarityincludeskinematicsimilarity,whilekinematicsimilarityincludesgeometricsimilarity.Hence,ratiosofforce,timeandlengtharesameunderdynamicsimilarity,andotherquantitiesarealsoequal.動(dòng)力相似包括運(yùn)動(dòng)相似，而運(yùn)動(dòng)相似又包括幾何相似。所以動(dòng)力相似包括力、時(shí)間和長(zhǎng)度三個(gè)根本物理量相似。兩系統(tǒng)的其它物理量由它們決定，也必然相似。Theinitialconditions(初始條件)andboundaryconditions(邊界條件)alsomustbecoincident