Resonant Scattering by Two Elastic Cylindrical Shells

The resonant scattering by two elastic cylindrical shells immersed in water is theoretically and experimentally studied. The shell axis are parallel; the incident plane wave direction of propagation is perpendicular to the shell axis. The scattering by the two shells is rewritten in a new way explaining the interferential behavior which is experimentally observed in the scattering process. The analysis of the scattering in terms of multiple interactions is also performed in order to evaluate the strength of the coupling between the two shells in relation to the gap between them. A numerical calculation of the temporal and frequency responses of the target submitted to an impulsive excitation is compared with experimental data obtained when the shells are aligned with regard to the incident wave direction of propagation. The agreement between the experimental and theoretical results is very good. Single shell resonances and "interaction resonances" related to the interferential behavior are detected. The geometrical and circumferential waves involved in the scattering process are also studied in order to explain the temporal and frequential responses.