简介:Theacousticperformanceofthestructureformeasuringcavitationnoiseistheoreticallyanalysed,andtwojudgingcriteriaoftheacousticperformanceofSTW(soundtransmissionwindow)arepresentedinthispaper.OneisofimpedancematchingbetweenworkingliquidandSTW:ρ1C1=ρ2C2.Theotherisofmaximumfrequency(orminimumwavelength)ofcavitationnoisespectrum:fmax≤c/60D(orλmin/D≥60).Ifeitherofthecriteriaismetreliablemeasuredresultsofcavitationnoisewillbeobtained.Thetheoreticalresultsareverifiedthroughexperi-ments.Accordingtothecriteria,thepaperanalysestheacousticperformanceofroutinelyusedplexiglassSTW.Theresultsshowthatintheresearchofclearwatercavitationtheimpedanceratio,2.18,doesnotsatisfyρ1C1=ρ2C2,andfmax≤C/60Dhardlyholdsforactualcavitationnoisespectrum.Therefore,plexiglassSTWisnotgoodenoughforsoundtransmission.Fromthispointofview,polyethyleneisbettersoundtransmissionmaterialthanplexi-glass.
简介:Inthisarticle,anewacoustictesttechniqueusingtowedmodelwasintroducedtostudyflownoisecausedbyasurfaceship.Theprojectofmodeltestwasbeproperlydesignedforacousticsignalcollectingandwiththehelpofappropriatedataprocessingmethoddifferentkindsofacousticsourcescouldbesuccessfullyidentified.Alotofworkaboutfuidnoisecouldbecarriedonwiththetowedmodel,andthenoisecorrespondingtolowfrequencywhichisespeciallyinterestedforitslongdistanceradiatingwithsmallattenuationcouldalsobestudiedinthisway.
简介:Thetipvortexcavitation(TVC)noiseofmarinepropellersisofinterestduetotheenvironmentalimpactsfromcommercialshipsaswellasforthesurvivabilityofnavalships.Duetocomplicatedflowandnoisefieldaroundamarinepropeller,atheoreticalapproachtotheestimationofTVCnoiseispracticallyunrealizable.Thus,estimationofprototypeTVCnoiselevelisrealizedthroughextrapolationofthemodelTVCnoiselevelmeasuredinacavitationtunnel.Inthisstudy,forthepredictionofprototypeTVCnoiselevelfromamodeltest,anovelscalinglawreflectingthephysicalbasisofTVCisderivedfromtheRayleigh-Plessetequation,theRankinevortexmodel,theliftingsurfacetheory,andotherphysicalassumptions.ModelandprototypenoisedatawereprovidedbySamsungHeavyIndustries(SHI)forverification.Inapplyingthenovelscalinglaw,similitudeofthespectraofnucleiisappliedtoassumethesamenucleidistributioninthetipvortexlineofthemodelandtheprototype.ItwasfoundthattheprototypeTVCnoiselevelpredictedbythenovelscalinglawhasbetteragreementwiththeprototypeTVCnoisemeasurementthantheprototypeTVCnoiselevelpredictedbythemodifiedITTCnoiseestimationrule.