LAUE URA CNRS 1373, Universite du Havre, Place Robert Schuman, 76610 Le Havre, France
The acoustic scattering from finite cylindrical objects endcapped by two hemispheres is studied. To explain the experimental resonance spectra when the object is parallelly insonified to the axis, a condition of phase matching is written on the meridian circumference. To apply this condition, it is necessary to know the phase velocity of surface waves along the different parts of the object. To verify this hypothesis, resonance identifications are realized. The identification diagrams are not easy to interpret. The lobe number is not equal to the antinode number, and these lobes do not have the same amplitude. An integral method will permit the knowledge of the acoustic pressure in the far field if the profile of the vibration state along the meridian line is sinusoidal. A good agreement is obtained between the theoretical and experimental studies. To confirm this hypothesis, a finite element method is developed. A 2-D problem is considered. A meridian plane and the water around the object is meshed. A sinusoid burst with several periods insonifies the object. The vibration amplitude of the surface of the object is determined in every way. The results confirm the hypothesis used in the integral method and allows the validation of the phase-matching condition. [sup a)]In memory to J. Carnet deceased in June 1994.