### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 5aPA6. Acoustic scattering from finite length cylinder bounded by two
spherical endcaps.

**J. Carnet
**

**
J. Dujardin
**

**
D. Decultot
**

**
G. Maze
**

**
**
*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.