Backscattering by a spherical elastic shell close to the air-water interface: comparison between experiment and modelling

Abstract : Backscattering by submerged elastic objects yields information about the object that can be used for both identification and classification. When the object is close to a boundary, the interactions between the object and boundary can lead to a very complex structure of the scattered signal, masking the free field response of the object. In this paper we discuss the special case where the object is submerged just beneath the air-water interface. The effect of the air-water interface on the backscattered field of an elastic spherical shell of small dimension (2a=3cm) was examined in the frequency range up to 800 kHz that corresponds to: ka=50. Simulations are based on a multiple scattering approach. The general form function calculated for different angles of incidence was compared with the results obtained for a thin shell in the free space. An experiment was carried out in the Laboratory on a thin spherical shell placed just beneath the air/water interface. The shell was insonified at different angles of incidence by a wide band transducer working in the frequency range [400 kHz-650 kHz]. This frequency domain was chosen in order to excite strong resonances associated with the A0 wave propagating along the shell surface. The resonances were clearly identified in the free field measured spectrum as well as in the numerical modeling. It was shown that in addition to geometrical reflections between the object and the air/water interface, strong interactions due to these resonances could be observed when the object is very close to the interface. Experimental results in the time domain were compared to exact computations for different angles of illumination and different distances of the shell from the air/water interfaces and the different echoes were identified. Moreover a simplified version of the backscattered field was obtained and its performances were checked against experimental data and exact calculations
Type de document :
Communication dans un congrès
Michael A Ainslie. Symposium held in memory of David E. Weston, Apr 2010, Cambridge, United Kingdom. Institute of Acoustics, Vol 32 (Pt2), pp.106-116, 2010
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https://hal.archives-ouvertes.fr/hal-00670261
Contributeur : Jean-Pierre Sessarego <>
Soumis le : mercredi 15 février 2012 - 09:05:50
Dernière modification le : lundi 29 janvier 2018 - 16:06:02

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  • HAL Id : hal-00670261, version 1

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Jean-Pierre Sessarego, Natalie Grigorieva, Paul Cristini, Gregory Fridman. Backscattering by a spherical elastic shell close to the air-water interface: comparison between experiment and modelling. Michael A Ainslie. Symposium held in memory of David E. Weston, Apr 2010, Cambridge, United Kingdom. Institute of Acoustics, Vol 32 (Pt2), pp.106-116, 2010. 〈hal-00670261〉

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