On analytical computation of acoustic scattering by prolate and oblate spheroids and its applications to ocean acoustics.

GONZALEZ, JUAN D.; LAVIA, EDMUNDO; BLANC, SILVIA; PRARIO, IGOR

Praga

Congreso; 26th IUGG General Assembly; 2015

International Union of Geodesy and Geophysics (IUGG)

The interior of the ocean is full of a great variety of objects whose shape can be approximated by a prolate spheroid (such as elongated fish, swimbladder fish, some phytoplankton, zooplankton and submergible vehicles) or by an oblate spheroid (such as other flattened type of fish, phytoplankton, zooplankton, submergible vehicles and also some fish shoals). Spheroidal wave functions have been used for over a century in dealing with scattering of sound by spheroids. These functions constitute analytical solutions of the wave equation when solving boundary value problems of acoustic scattering in prolate and oblate spheroidal coordinates. The advantage of considering analytical solutions of the wave equation lies upon the fact that they solve it exactly and consequently they don?t need additional validation. However, their computation is a complex task and it requires numerical efficient methods. Only a few of the codes that have been developed and documented in the literature for certain particular scenarios (solutions valid for far-field conditions, limited scatterer size-wavelength ratios, ideal scatterers), are easily available. The purpose of this presentation is to provide the theoretical results obtained when modelling the acoustic scattering of soft, liquid and rigid prolate and oblate spheroids for an extended range of conditions of interest in ocean acoustics. Ad-hoc codes were implemented. Their predictions are compared with measurements for several marine organisms. Differences involved in computing prolate spheroidal wave functions and oblate ones are discussed in detail.