流体力学C名词解释.docx
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流体力学C名词解释
Chapter1Fluidstatics流体静力学
1.连续介质假定(Continuumassumption):
Therealfluidisconsideredasno-gapcontinuousmedia,calledthebasicassumptionofcontinuityoffluid,orthecontinuumhypothesisoffluid.流体是由连续分布的流体质点(fluidparticle)所组成,彼此间无间隙。
它是流体力学中最基本的假定,1755年由欧拉提出。
在连续性假设之下,表征流体状态的宏观物理量在空间和时间上都是连续分布的,都可以作为空间和时间的函数。
2.流体质点(Fluidparticle):
AfluidelementthatissmallenoughwithenoughmolestomakesurethatthemacroscopicmeandensityhasdefinitevalueisdefinedasaFluidParticle.宏观上足够小,微观上足够大。
3.流体的粘性(Viscosity):
isaninternalpropertyofafluidthatoffersresistancetosheardeformation.Itdescribesafluid'sinternalresistancetoflowandmaybethoughtasameasureoffluidfriction.流体在运动状态下抵抗剪切变形的性质,称为黏性或粘滞性。
它表示流体的内部流动阻力,也可当做一个流体摩擦力量。
Theviscosityofagasincreaseswithtemperature,theviscosityofaliquiddecreaseswithtemperature.
4.
牛顿内摩擦定律(Newton’slawofviscosity):
5.
Thedynamicviscosity(动力黏度)isalsocalledabsoluteviscosity(绝对黏度).Thekinematicviscosity(运动黏度)istheratioofdynamicviscositytodensity.
6.Compressibility(压缩性):
Asthetemperatureisconstant,themagnitudeofcompressibilityisexpressedbycoefficientofvolumecompressibility(体积压缩系数)к,arelativevariationrate(相对变化率)ofvolumeperunitpressure.
Thebulkmodulusofelasticity(体积弹性模量)Eisthereciprocalofcoefficientofvolumecompressibilityк.
7.流体的膨胀性(expansibility;dilatability):
Thecoefficientofcubicalexpansion(体积热膨胀系数)αtistherelativevariationrateofvolumeperunittemperaturechange.
8.表面张力Surfacetension:
Apropertyresultingfromtheattractiveforcesbetweenmolecules.-----单位长度所受拉力
9.表面力Surfaceforce——istheforceexertedonthecontactsurfacebythecontactedfluidorotherbody.Itsvalueisproportionaltocontactarea.作用在所研究流体外表面上与表面积大小成正比的力。
Stress(应力)isthesurfaceforceonperunitarea.
10.
质量力Massforce——Theforceactingoneveryfluidmassparticlewithinthecontrolbody.Itsvalueisproportionaltoitsmass.Massforceisalsoknownasbodyforce.作用在流体的每一个流体质点上,其大小与流体所具有的质量成正比。
11.EulerEquilibriumEquations欧拉平衡微分方程(分量式)1775年
PhysicalMeaning:
Forthefluidinequilibrium,surfaceforcecomponentspermassfluidareequaltomassforcecomponentspermassfluid.Pressurevariationrateinaxesdirectionsareequaltomassforcecomponentsperunitvolumeinaxesdirectionsrespectively
12.constant-pressureSurface(等压面)——asurfacethatthepressureofeverypointinliquidisequal.Commonconstant-pressuresurfacesarefreeliquidsurfaceandinterfaceoftwounmixedfluidsinequilibrium.平衡流体中压强相等的点所组成的平面或曲面。
13.PressureDistributionintheStaticFluid重力场中流体的平衡
Conclusions:
1.Pressureatapointinastaticfluidundergravityincreaseslinearlywithdepth.
2.Pressureatapointinastaticfluidundergravityisequaltothesumofthepressureatthefreesurfaceandthefluidspecificweighttimingdepth.
3.constant-pressuresurfaceinastaticfluidundergravityisahorizontalplane.
4.Extended:
whilethepressureatapointandthedepthdifferencebetweentwopointsareknown,thepressureatanotherpointcanbecalculated.
14.Absolutepressure(绝对压力),Gagepressure(相对压力,又称“表压力”),andVacuum(真空度):
表压力=绝对压力-大气压力;真空度=大气压力-绝对压力
15.FluidinRelativeEquilibrium(相对静止流体)Equationofconstant-pressuresurface(等压面方程):
a)
UniformLinearAcceleration等加速度直线运动流体:
b)UniformRotationaboutaVerticalAxis等角速度旋转流体:
Chapter2basicequationsoffluidmechanics
16.迹线pathline:
thetraceafterasingleparticletravelsinafieldofflowoveraperiodoftime.流体质点的运动轨迹曲线
17.
流线streamline:
acurvethatshowthedirectionofanumberofparticlesatthesameinstantoftime.某一时刻处处与速度矢量相切的空间曲线--瞬时性。
18.Stream-tube(流管)——Consideraclosedcurve(notstreamline)intheflowfield,thendrawstreamlinesthrougheverypointonit,soastoformatube-shapingspacewhosewallsarestreamlines.Thistubeiscalledthestream-tube.在流场中任取一个有流体从中通过的封闭曲线,在曲线上的每一个质点都可以引出一条流线,这些流线簇围成的管状曲面称为流管。
19.Tube-flow流束——Fluidfullingthestreamtubeiscalledthetube-flowandthelimitofatube-flowisastreamline.流管内的全部流体称为流束。
20.Ministream-tube微小流束——Thestreamtubewithaninfinitesimalsectionissaidtobemini-streamtube.Streamlineistheextremecaseofmini-streamtube.截面无穷小的流束。
21.Totalflow总流——Totalofcountlessmini-streamtubesiscalledtotalflow.包含流动中所有的微小流束。
22.
Crosssection(过水断面)---Thesectionisperpendiculartothedirectionoffluidflow.(suchaspipeflowandchannelflow)与流束或总流流线成正交的断面。
23.Discharge(流量)---Amountoffluidpassthroughacrosssectionperunittime(suchasthesectioninthechannelorpipe).单位时间内通过某一过水断面的流体体积称为体积流量,简称流量。
24.Meanvelocity断面平均流速---Thevelocitiesofpointsonthesamecrosssectioninthetotalflowaredifferent,sousuallyanaveragevelocityisusedinsteadoftherealvelocityoverthecrosssection,thisaveragevelocityiscalledthemeanvelocity.
25.
Uniformflow均匀流:
isdefinedasuniformflowwhenintheflowfieldthevelocityandotherhydrodynamicparametersdonotchangefrompointtopointatanyinstantoftime(inwhichthecrosssectionofeachstreamtuberemainsunchanged.流场中每一空间点的各运动参数(速度,压力)不随空间位置而变化。
26.Nonuniformflow非均匀流:
Flowsuchthatthevelocityvariesfromplacetoplaceatanyinstant.
27.Steadyflow恒定流:
theflowwhosemotionfactorsdon’tchangewithtime.流场中所有的运动要素不随时间变化.
28.Unsteadyflow非恒定流:
theflowthatatleastoneofitsmotionfactorschangeswithtime.流场中至少有一个运动要素随时间变化.
29.Onedimensionalflow(一元流动)--allmainvariablesintheflowfieldcanbecompletelyspecifiedbyasinglecoordinateifthevariationofflowparameterstransversetothemainstreamdirectioncanbeneglected.流动参数只与一个坐标变量有关。
30.Twodimensionalflow(二元流动)-fluidmotionfactorsarefunctionoftwospacecoordinates.流动参数与两个坐标变量有关。
31.Three-dimensionalFlow(三元流动):
Fluidflow’smotionfactorsarefunctionsofthreespacecoordinates.流动参数与三个坐标变量有关。
32.System(系统)——isasetofdefinitefluidparticlesselectedintheinterestofresearcher.由确定的流体质点组成的流体团或流体体积V(t)。
系统边界面S(t)在流体的运动过程中不断发生变化。
反映了拉格朗日观点
33.Controlvolume(控制体CV)——isdefinedasaninvariablyhollowvolumeorframefixedinspaceormovingwithconstantvelocitythroughwhichthefluidflows.相对于坐标系固定不变的空间体积V。
是为了研究问题方便而取定的。
反映了欧拉观点
ForaCV:
1)itsshape,volumeanditscscannotchangewithtime.
2)itisstationaryinthecoordinatesystem.(inthisbook)
3)theremaybetheexchangeofmassandenergyonthecs.
34.Controlsurface控制面:
thesurfaceareacompletelyenclosestheCV.边界面S称为控制面。
35.
differentialformofcontinuityequation微分形式的连续性方程
Forincompressiblefluid
For2-Dincompressibleflow
Physicalmeaning:
Thenetmassdischargeenteringthecontrolvolumeisequaltothemassincreasedinunittimeduetothechangeindensity.
Fitfor:
Steadyflow,unsteadyflow,compressibleandincompressiblefluid,idealfluidandrealfluid.
36.
Integralformofcontinuityequation积分形式的连续方程
Physicalmeaning:
在单位时间内,由于控制体内密度变化引起的质量变化量(增加量或减少量)与通过控制体表面的质量净流出量(流出与流入的质量差)之和等于零。
Steadyflow定常流动
incompressiblefluid不可压缩流体
37.MotionDifferentialEquation运动微分方程
ForIDEALFLOW
forViscousFlow
38.BernoulliEquation伯努利方程
(1)steadyflow定常流动
(2)incompressibleflow不可压缩
(3)integrationalongastreamline沿流线积分
(4)massforceisapotentialforce质量力有势
Forstreamline
Forcompressibleflowingravityfield
Forcompressibleflowwithfluidmachineryingravityfield
z(m)——theelevationheightabovedatumsurfaceo-o,calledtheelevationhead(位置水头).
p/(g)——risingheightoffluidwithunitweightundertheactionofpressureP,calledthepressurehead(压力水头).
u2/(2g)——risingheightoffluidwithunitweightundertheactionofvelocityV,calledthevelocityhead(速度水头),denotedashu
——thelostmechanicalenergyfrom1to2pointsperunitweightfluid
——Theeffectiveenergyobtainedaftertheunitweightoftheliquidflowsthroughthepump.单位重量液体流经泵后获得的有效能量。
Headofdelivery扬程
Thesumofthemiscalledthetotalhead(总水头),denotedasH.
Pumppower泵功率:
Fortheideal-fluidtotalflow理想流体总流的伯努利方程
forthereal-fluidtotalflow实际流体总流的伯努利方程
39.momentumintegralequation动量积分方程
ForCV
——sumofthefluidmomentumchangeinCVandthenetoutflowmomentuminCS,isequaltotheresultantforce.
Steadyflow:
40.Moment-of-momentumintegralequation动量矩积分方程
Forsteadyflow:
[流出动量矩]CS–[流入动量矩]CS=[合外力矩]CV+CS
41.Forcesonbend(弯头)
42.fluidjetsondeflector(导流板)
43.Sprinkler(喷水器)
角速度:
固定所需力矩
Chapter3PipeFlowandBoundaryLayerTheory(管流和边界层概述)
44.Laminarflow(层流):
Inthefluidflowthefluidparticlesmovealongsmoothpathinlayerswithouttransversevelocityinthedirectionofmainflow,onelayerglidessmoothlyoveranadjacentlayer.
45.Turbulentflow(紊流,湍流)orTurbulence:
Ifthefluidparticleshaveatransversevelocitynormaltothemainflowdirection,thatleadstoparticlesmixingupeachother,withaviolenttransverseinterchangeofmomentum.Thisisturbulentflow(紊流,湍流)orturbulence.
46.Reynoldsnumber雷诺数:
isusedtodescribethecharacteristicofflow.
47.Wettedperimeter(湿润长度):
Thelengthofwallcontactedwithliquid.
48.thehydraulicdiameter(水力直径)DH:
Thecharacteristicdimensionofnoncirculartube.
49.HeadLoses(能头损失,或水头损失):
thetotalenergylossesperunitweight(单位重量流体所损失的机械能为能头损失(水头)),whichduetotheresistancebetweentwosectionsofgraduallyvariedflow.(流体流动,克服粘性内摩擦力,消耗机械能为热能.)
50.FrictionLoss沿程水头损失(hλ):
Intheflowthroughastraighttubewithconstantcrosssection,theenergylossincreaseslinearlyinthedirectionofflowandthelossiscalledfrictionloss.(