Resonance scattering in waveguides: Acoustic scatterers

Abstract

In this paper,a coustics catteringin shallowa nd deepi nhomogeneouwsa veguidesis analyzed. The full acousticw avee quationt hat describesth e scattereda nd reflectedw avef ields,a s well as all multipathingw ithin the scatterera nd the waveguidei,s employed.T he explicit finite differenceti me integrationa nd the k-w transformi n the spaced omain (pseudospectral method) were utilized. Properlyc hosenb oundaryc onditionse nabledt he authorst o model both shallowa nd deepo ceansT. he pseudospectraml ethodw as comparedw ith the explicit finite differencet echnique( seeA ppendix). The pseudospectraml ethodc an be valuablef or modelingd ifferentu nderwaterw avep henomenaI:t is characterizedb y much smaller numericald ispersionth an the conventionafl inite differencem ethod.T he resultss howt hat in shallowo cean,s trongr esonancec ouplingb etweent he underwaters catterera nd the waveguide may occur.A n important conclusiono f this paper is that in a limited aperturee xperiment when the acousticr eflectionsa re beyondt he recordinga perture (due to the finite length of the recordingc able), the measuredd ata are mainly representedb y the primary diffractiona rrivals and "diffractionr esonances.I"n this paper,a detailedd iscussionw ill be giveno n the acoustic scatteringi n an inhomogeneouws aveguide.( For the sakeo f simplicity,a n acoustics catterero f the rectangulars hapew as considered). Different complexities( elastics catterersm, ore complicateds tructureso f the index of refractioni n the water, etc.) will be compoundedin the original model and reported elsewhere