3rd French conference on acoustics
J. Phys. IV France 04 (1994) C5-885-C5-888
Signal rétrodiffusé par un corps élancé de révolutionF. YWANNE, M. TRAN VAN NHIEU and F. VARLET
Thomson Sintra Uwa, 1 Avenue Aristide Briand, 94117 Arcueil, France
The echoes backscattered in the far field by a rigid prolate spheroid at low and medium frequencies are computed and commented. The so-called slender-body aproximation is applied to express the pressure backscattered by the body when insonified by a harmonic plane wave. The impulse response is then calculated by Fast Fourier Transform for different angles of incidence. The computed echoes exhibit two main peaks, one narrow and one spread out, corresponding respectively to the reflected echo and to the diffracted waves that encircle the body once ("creeping waves"). The time of arrival of the specular echo corresponds to that provided by Geometrical Optics. An explanation, resulting from the analysis of the computed echos, is proposed for the times of arrival of the diffracted waves at oblique incidence. However, a theoretical study is required to check the validity of that explanation.
© EDP Sciences 1994