ASA 127th Meeting M.I.T. 1994 June 6-10

5aUW9. Acoustic scattering from immersed axisymmetric objects. Cylindrical shell limited by hemispherical endcaps.

Dominique Decultot

Florence Lecroq

Gerard Maze

Jean Ripoche

Lab. d'Acoust. Ultrason. et d'Electron. LAUE), URA CNRS 1373, Univ. du Havre, Place R. Schuman, 76610 Le Havre, France

The study of the acoustic scattering from axisymmetric objects is based on the works that have been previously carried out in this field for objects with ``simple'' shapes (plates, cylinders, cylindrical shells). The objects under investigation consist of a cylindrical shell limited by two hemispherical shells. The experimental results presented in the form of resonance spectra are obtained by the MIIR (method of isolation and identification of resonances). A complete study for various excitation angle allows one to locate particular directions where the resonant phenomenon is important. For axial excitation, the results are interpreted by means of the condition of resonance formation (deduced from the phase matching) in the meridian plane of the objects. This condition takes into account the phase velocities of the waves propagating on the hemispherical parts and on the cylindrical part. For normal excitation experimental results are compared to those obtained from infinite cylindrical shell. Other particular directions of excitation are highlighted in this study. These results obtained for axisymmetric objects (stainless steel) allow the understanding of the influence of the shape of the objects on the surface wave propagation [Decultot et al., J. Acoust. Soc. Am. 94, 2916--2923 (1993)].