工程流体力学英文版第七章pdf_资料下载.pdf

工程流体力学英文版第七章pdf_资料下载.pdf

《工程流体力学英文版第七章pdf_资料下载.pdf》由会员分享，可在线阅读，更多相关《工程流体力学英文版第七章pdf_资料下载.pdf（23页珍藏版）》请在冰豆网上搜索。

TheoreticalFMExperimentalFMComputationalFMb.Theneedofengineeringpractice2.Whyneedwestudy?

1.DynamicSimilitudeofFluidMotion?

2.SimilitudePrinciples?

3.DimensionalAnalysis,RayleighMehtod,Buchingham?

Method?

4.ModelExperiment3.Contents:

?

1.DynamicSimilitudeofFluidMotionDynamicSimilitudeofFluidMotion:

Atanytime,alltheparametersofthemodelandprototypeareinthesameratiothroughouttheentireflowfield:

Geometricsimilitude（basic）Motionsimilitude（result）Dynamicsimilitude（condition）prototypemodel1.Geometricsimilitude（basicandthemostobviousrequirement）Themodelisanexactgeometricreplicaoftheprototype.Allthelineardimensionsofthemodelandprototypeareinthesameratioscaleratiobetweenmodelandprototype1212lmmmlldClld=prototypemodelscaleratio:

ratioofarea:

ratioofvolume:

1212lmmmlldClld=222AlmmAlCCAl=333lmmlCCl=prototypemodel2.MotionSimilitude（result）Velocityofthemodelandtheprototypeareinthesameratiothroughouttheentireflowfield.ratioofvelocity312123VmmmVVVCVVV=prototypemodelratiooftime:

ltmmmVCVltCVltC=ratioofacceleration:

ratioofvolumerate:

ratioofkinematicviscosity:

ratioofrotation:

lVmmmtCltVCVltC=2VVammmtlCCVtaCaVtCC=3323lQlVmtmmCltQCCCQClt=222llVmtmmCltCCCClt=VmmmlCVlCVlC=3.Dynamicsimilitude（condition）Alltheforcesthatactoncorrespondingmassesinthemodelandtheprototypeareinthesameratiothroughouttheentireflowfield.312123FmmmFFFCFFF=prototypemodel22FmalVmmmaCCCCCCma=4.RelationshipGeometricsimilitude（basicandthemostobviousrequirement）MotionSimilitude（result）Dynamicsimilitude（condition）return?

2.SimilitudePrinciples（?

2.1NewtonSimilitudePrinciples2.2Eulernumber,Froudnumber,Reynoldsnumber,Machnumber2.1NewtonSimilitudePrinciplesOr:

DynamicSimilitudeNeequals22FlVmmmmmmVtmaCCCCmaVt=221FlVCCCC=2222mmmmFFNelVlV=2.2Eulernumber,Froudnumber,Reynoldsnumber,Machnumber22FNelV=（）2222plpEulVV=22FNelV=（）（）2pFpApl=3gFmgglg=1.SimilitudePrincipleofflowactedbypressureforcePressureforce?

22mmmppEuVV=2.SimilitudePrincipleofflowactedbygravityGravity:

mmmVVFrglgl=Eulernumber:

Froudnumber:

22FNelV=RemmmmVlVl=22mmmVVCaEE=2dddduuFAAlyy?

=?

2sFEAEl=Viscousforce?

3.SimilitudePrincipleofflowactedbyviscousforce4.SimilitudePrincipleofflowactedbyelasticforceElasticforce?

aE=2222VVCaaa=（）12VMCaa=Reynoldsnumber:

Forfluid:

2Ea=Machnumber:

3.DimensionalAnalysisDimension:

UnittypesofphysicalvariablesFundamentaldimension:

thedimensionoftimeT（hour,minute,second）thedimensionoflengthL（m,cm,mm）thedimensionofmassM（ton,kilogram,gram）thedimensionoftemperature?

（oC,K）1.PrincipleofidenticaldimensionsforphysicalequationsDeriveddimension:

velocity:

LT-1acceleration:

LT-2density:

ML-3force:

MLT-2pressure:

ML-1T-2dynamicviscosity:

ML-1T-1kinematicviscosity:

L2T-1HgVgpZ=+22LLLLPrincipleofidenticaldimensionsforphysicalequations:

Aprocessinvolves:

y,x1,x2,x3,xnTherelationshipbetweenyandy,x1,x2,x3,xncanbeexpressed:

example2.IndicialMehtod（RayleighMethod）312123.aaaannykxxxx=Thenumberofindependentdimensionlessgroupsofvariablesneededtocorrelatethevariablesinagivenprocessisequalton-m,wherenisthenumberofvariablesinvolvedandmisthenumberdimensionsincludedinthevariables.example3.BuckinghamMethod（groupMethod）（）123,0nxxxx=（）123,0mf=312123.iiaaaamimiiixxxxx+=?

4.ModelexperimentGeometricsimilitude（basic）Motionsimilitude（result）Dynamicsimilitude（condition）Similitudeofinitialandboundaryconditionprototypemodel1.ConditionofSimilitudeOnetypeofflowGeometricsimilitudeSimilitudeofinitialandboundaryconditionThesamesimilitudedimensionlessnumberdifficult:

a.Geometricsimilitude=LLDD2.Howtodesign:

b.Thesamesimilitudedimensionlessnumber（Fr,Re,Eu,Ca,Ma）Re=LVVLLgVgLV=if=,kkLV1=gg=Generally:

1/2VLkk=1=kkLV?

=1=kkkLV12/1=kkkLL2/3kkL=if101=kL,6231110123.k/v=?

=*themostimportantforce（dimensionlessnumber）*laminarorcompleteturbulenceroughzone3.Modelexperiment