ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

3aSA4. Acoustic scattering from a hemicapped cylindrical shell with substructures.

Weiping Zhang

Component Products Group, Motorola, 1301 E. Algonquin Rd., Schaumburg, IL 60196

Takeru Igusa

Jan D. Achenbach

Northwestern Univ., Evanston, IL 60208

This paper extends the study on acoustic radiation of axisymmetric submerged shells of finite length to the scattering problem. A modal-based method is developed to determine the scattering from finite shells insounified by plane incident waves. A surface variational principle provides the acoustic impedance relationship between the surface pressure and displacement fields, which are expanded into a series of shape functions. Lagrange multipliers are introduced in a Lagrange formulation of the dynamic analysis to account for the interaction between the shell and internal substructures. Surface and far-field pressures scattered from the elastic shell are calculated. It is found that, at certain angles, the scattered pressure field has pronounced peaks, particularly as the incident frequency increases. A wave number domain analysis is performed on the surface displacement field. A dominant wave number is found which accounts for the high directivity pattern of the far field. The effect of substructures on the far field is also investigated.