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1、AppliedScientificResearch49:191-215,1992.©1992KluwerAcademicPublishers.PrintedintheNetherlands.191Theoryofcross-correlationanalysisofPIVimagesRICHARDD.KEANE&RONALDJ.ADRIANDepartmentofTheoreticalandAppliedMechanics,UniversityofIllinoisatUrbana-Champaign
2、,216TalbotLab.,104S.WrightStreet,Urbana,IL618011793,U.S.A.Abstract.Toimprovetheperformanceofparticleimagevelocimetryinmeasuringinstantaneousvelocityfields,directcross-correlationofimagefieldscanbeusedinplaceofauto-correlationmethodsofinterrogationofdou
3、ble-ormultiple-exposurerecordings.Withimprovedspeedofphotographicrecordingandincreasedresolutionofvideoarraydetectors,cross-correlationmethodsofinterrogationofsuccessivesingle-exposureframescanbeusedtomeasuretheseparationofpairsofparticleimagesbetweens
4、uccessiveframes.Byknowingtheextentofimageshiftingusedinamultiple-exposureandbyaprioriknowledgeofthemeanflow-field,thecross-correlationofdifferentsizedinterrogationspotswithknownseparationcanbeoptimizedintermsofspatialresolution,detectionrate,accuracyan
5、dreliability.Forthedirectcross-correlationmethodofsingle-exposure,double-framesystemswhichmodelvideoarraydetectorinterrogationandofdouble-exposuresingle-framesystemswhichgeneralizeearlierdirectauto-correlationmethodsofinterrogationofphotographicrecordi
6、ngs,optimalsystemparametersarerecommendedforarangeofvelocityfieldsinordertoeliminatesignalbiasandtominimizelossofsignalstrength.Thesignalbiasresultingfromvelocitygradientsinauto-correlationanalysiscanbeeliminatedincross-correlationinterrogationbyapprop
7、riatechoiceoftheoptimalparameters.Resolution,detectionrate,accuracyandreliabilityarecomparedwithdirectauto-correlationmethodsfordouble-andmultiple-pulsedsystems.Keywords:PIV,cross-correlation,auto-correlation1.IntroductionParticleImageVelocimetry(PIV)u
8、sesimagesofmarkerparticlesinafluidflowtomeasureinstantaneousvelocityfieldsinexperimentalfluidmechanics.Ingeneral,theparticlesareilluminatedbypulsedsheetsoflightatprecisetimeintervalstoproduceimagesthatarerecordedonphotographicfilmoronav
