Monostatic and bistatic acoustic scattering from smooth and rough elastic cylinders insonified by directional sonars

Abstract

Acoustic scattering from cylinders has been previously studied extensively for idealized incident plane waves and point receivers. However, the more realistic case of scattering from cylinders insonified by directional sonars has received limited attention. Operational sonars are directional and transmit waves that spread spherically. Due to the spherical spreading, the overall scattered pressure levels are affected and the cylinder is insonified across a continuum of oblique incident angles, even at broadside incidence. The obliqueness in the incident field, in turn, influences the structure of the scattering spectrum by exciting guided wave natural modes. A recently derived theory, accounting for the above realistic effects, is tested against laboratory measurements involving both smooth and rough elastic cylinders, spanning a range of scattering geometries and roughness profiles. The effects of bistatic angle between the source and receiver on overall scattered pressure levels and resonances are investigated and compared with results from the monostatic geometry. The influence of correlation length and root mean square roughness on the scattered field is also studied.