Modelling and measurement of backscattering from partially water-filled cylindrical shells

Humphrey, Victor, Wang, Lian Sheng and Jayasundere, Nisabha (2009) Modelling and measurement of backscattering from partially water-filled cylindrical shells. Papdakis, J.S. and Bjorno, L. (eds.) Third International Conference on Underwater Acoustic Measurements, Technologies and Results, Nafplion, Greece. 20 - 25 Jun 2009. 8 pp .

Abstract

The backscattering from partially water-filled cylindrical shells has been studied using finite element (FE) analysis and experimental measurements for low to medium frequencies, corresponding to 2 < ka < 30 (where a is the shell outer radius). For a partially-filled shell, filled to three quarters of the inner diameter, backscattering has been investigated numerically as a function of the elevation angle of the incident wave, and in particular as the wave direction changes from horizontal to vertical. Comparisons with fully air-filled and fully water-filled shells indicate that the shell resembles the former when the wave is incident from above and the latter when the wave is incident horizontally. The experiments were performed in a reservoir, using horizontal incidence and wideband Ricker pulses generated by a parametric array. The short duration of the Ricker pulses made it possible to observe a number of returns after the specular return for a shell with a high filling fraction; these included contributions due to S0 waves generated at the front and back walls of the shell, and the back wall return. Inversion of the FE model data enabled the expected waveforms to be predicted; the measurements were in very good agreement with the predictions

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Contributors

Author: Victor Humphrey

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