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

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

**Pei-Tai Chen
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*Dept. of Naval Architect., Natl. Taiwan Ocean Univ., 2 Pei Ning Rd.,
Keelung 202, Taiwan, Republic of China
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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.]