Transient acoustic scattering from a small underwater vehicle in shallow water
Publish date: 2005-01-01
Report number: FOI-R--1713--SE
Pages: 25
Written in: English
Abstract
A numerical study is presented of transient acoustic scattering from a body shaped as a small underwater vehicle (the Hugin 1000 AUV) immersed in shallow water. The environment is modelled as a 60 m deep water column with a thermocline at mid-depth overlying a soft fluid seabed. Transient pulses from a vertically directive source with center frequencies in the range 0.5 kHz - 16 kHz are considered, with the source at depth 15 m and the AUV located at range 500 m at varying depths. The scattered echoes are recorded by a vertical receiver array with center at the source. Predictions of the transient target echoes are computed with two fast approximative techniques (i) the TKS method based Kirchhoff scattering and (ii) the ERS method derived from acoustic ray theory. The accuracy of these techniques is assessed in the low-frequency cases by comparisons with accurate full-field solutions computed with a (iii) high-order boundary integral equation (BIE) method. The influence of the depth, the interior structure, and an optimized multi-layered anechoic coating on the transient target signature of the AUV is investigated.