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

4pSAa2. Formulation of structure--acoustic systems by using acoustic radiation modes.

Pei-Tai Chen

Dept. of Naval Architect., Natl. Taiwan Ocean Univ., 2 Pei Ning Rd., Keelung 202, Taiwan, Republic of China

The dynamic characteristics of surface acoustics for submerged bodies under mono-frequency oscillations were analyzed in a previous study [ 2918(A) (1994)] in which surface radiation pressure and velocity modes were established. The present analysis using these acoustic modes formulates the dynamic response for submerged elastic structures. The degree of freedom for the structural equations is expressed in the normal direction of the wetted surface of the structures. Coupling the elastic equation with the pressure and velocity modes leads to a symmetric matrix equation where the unknown variables are the modal amplitudes of the velocity modes. The matrix equation is composed of two parts (1) the structural effect (2) a diagonal matrix with the elements relating to the modal radiated and reactive powers. The significance of the formulation is the description of structure--acoustic systems in terms of acoustic radiation modes that provide a clear identification of responses pertaining to radiating or nonradiating as well as the radiation patterns of respective radiation modes. Numerical examples for a slender spheroidal elastic thin shell with a concentrated mass attached are examined in the present analysis to demonstrate the variation of radiation patterns on the effect of concentrate masses. [Worked supported by Chinese National Science Foundation.]