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

## 5aUW7. Scattering by an elastic shell with nonconcentric cylindrical
surfaces: Generalized Debye series expansion.

**E. Danila
**

**
J.-M. Conoir
**

**
J.-L. Izbicki
**

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

*
*
The scattered pressure by a solid elastic shell defined by two
nonconcentric cylindrical surfaces is considered; the cylinder axes are
parallel. The shell is immersed in a fluid and is excited by a monochromatic
plane wave impinging on it normally to the axis. The generalized Debye
expansion (GDE) formalism is used to physically analyze all the local
interactions involving in the scattering process. Two cylindrical coordinate
systems, each associated with one cylindrical surface, are introduced. With
this choice, all the needed cylindrical wave functions can be written either in
one system or the other thanks to the Graf addition theorem and the boundary
conditions can be simply expressed; the scattered pressure can be calculated.
It is also possible to relate the elements of the S matrix to the local
interaction coefficients, i.e., reflexion and transmission modal coefficients
coming from the GDE. In next future, it allows to obtain an expression of the
background which is useful to calculate the target resonances.