流体静力学方程和应用ppt课件.ppt

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1、Chapter1FluidFlow1234Inindustry,eithertherawmaterialortheproductsarefluids.Thebehavioroffluidsisimportanttoprocessengineeringgenerallyandconstitutesoneofthefoundationsforthestudyofunitoperations.Thechaptersofthissectiondealwiththoseareasoffluidmechanicsthatare

2、importanttounitoperations.5Fluidstatics(流体静力学):fluidatrestwhichtreatsfluidsintheequilibriumstateofnoshearstress.Fluiddynamics(流体动力学):fluidinmotionwhichtreatsfluidswhenportionsofthefluidareinmotionrelativetootherparts.Twobranchesoffluidmechanics6CHAP1.1FluidStati

3、csandItsApplications流体静力学及其应用Content1.1.1NATUREOFFLUIDS1.1.2HYDROSTATICEQUILIBRIUM1.1.3.APPLICATIONSOFFLUIDSTATICS71.1.1NATUREOFFLUIDS1.Flowability(流动性)2.Density3.Pressure8OneshapeAnothershapeFluidlayerslideoveroneanothershearstressesandviscosityexist.1.Flowabil

4、ity(流动性)Afluidisasubstancethatdoesnotpermanentlyresistdistortion.9２.DensityUnitofdensity:SIunit:kg/m3cgsunit:g/cm3fpsunit:lb/ft310Usuallyρsolid>ρliquid>ρgasThedensityofallfluidsdependsonthetemperatureandpressureρ=f(T,P)Forliquid:Forgases:11incompressiblefluid不可压

5、缩流体thedensitychangesonlyslightlywithmoderatechangesintemperatureandpressure.compressiblefluid可压缩流体thechangesindensitywithtemperatureandpressurearesignificant.12ρofidealgases:IfT=273K,P=1atm:13Sourceofdensitydata：handbook,Appendix6Densityofmixture:liquidmixtureWh

6、ereai----massfractionofcomponentsinthemixture14GasmixtureWhereψi----molefractionorvolumefractionofcomponentsinthemixtureNote:thedifferenceofdensityandspecificgravity153.PressureThepressureinastaticfluidisasurfaceforceexertedbythefluidagainstaunitareaofthewallsof

7、itscontainer.scalarquantitysameinalldirections.16Unitofpressure:SIunit:Pa(N/m2)others:atm,mmHg,mH2O,kgf/cm2,bar,at,psi(lbf/in2)1at:一工程大气压，俗称一公斤力17Threekindsofpressure:GaugepressureZeroabsolutepressureAtmosphericpressurevacuumAbsolutepressureFig.Therelationofthre

8、ekindsofpressureAbsolutepressureGaugepressureDegreeofvacuum(orvacuum)18Gaugepressure=absolutepressure–localatmosphericpressureVacuumpressure=atmosphericpressure–local