Acoustic harmonic radiation and scattering from shells of revolution using finite element and internal source density methods

Abstract

Acoustic axisymmetric harmonic radiation and scattering from fluid-loaded shells of revolution is addressed in the present paper using an in-vacuo modal vector expansion for the velocity field of the shell. The in-vacuo modal vectors for a specific shell are obtained via the use of finite element methods. As a result of the fluid loading the in-vacuo modes of the shell become coupled; hence, the modal velocity coefficients are described by a coupled set of algebraic equations which include mode-dependent mechanical impedances for the shell and mode-dependent acoustic radiation impedances for the fluid. The mode-dependent acoustic radiation impedances are obtained via the use of an internal monopole source density method. This method eliminates the need to use surface integral equation methods with their inherent problems to evaluate the acoustic radiation impedances. Extensive numerical results are presented for spheroidal and spherical shells. In-vacuo mode shapes and natural frequencies are first presented and then used to obtain the associated acoustic radiation impedances. Finally, the response of fluid-loaded point excited spherical and spheroidal shells are presented and discussed.