三维空泡回射流的理论研究（英文）

三维空泡回射流的理论研究（英文）Theoretical study of three-dimensional bubble acoustic backscatterAcoustic backscatt

三维空泡回射流的理论研究（英文） Theoreticalstudyofthree-dimensionalbubble acousticbackscatter Acousticbackscatterfrombubblesisanimportant phenomenoninunderwateracoustics.Theaimofthis paperistostudythetheoreticalaspectsofacoustic backscatterfromthree-dimensionalbubblecloudsusing theKirchhoffapproximation. TheKirchhoffapproximationisawidelyusedmethod forpredictingacousticbackscatterfromscatterers.It assumesthatthescattererissmallcomparedtothe wavelengthoftheincidentsoundandthatthesound fieldisweaklyperturbedbythescattering.Themethod modelsthescatteredfieldasasuperpositionofplane waves,eachofwhichhasthesamefrequencyandtravels inadifferentdirection. Inthecaseofbubbleclouds,thescattererisnota single,discreteobjectbutathree-dimensional distributionofbubbles.Eachbubblescatterssound wavesindependently,andthescatteredwavesinterfere togiverisetothebackscatteredfield.Toaccountforthis, wemodelthebubbledistributionasacollectionofsmall, sphericalscatterersandapplytheKirchhoff approximationseparatelytoeach. Thescatteredfieldfromasingle,sphericalbubble canbecalculatedanalyticallyusingtheMiesolutionto thewaveequation.TheMiesolutiongivesthescattered fieldasaseriesofsphericalharmonics,eachofwhichhas adifferentamplitudeandphase.TheKirchhoff approximationthenapproximatesthescatteredfield fromasinglebubbleasasuperpositionofplanewaves, eachofwhichcorrespondstoadifferentspherical harmonic.