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

4pSAa8. What is a mode?

Paul E. Barbone

Dept. of Aerosp. & Mech. Eng., 110 Cummington St., Boston University, Boston, MA 02215

D. G. Crighton

University of Cambridge, Cambridge CB3 9EW, UK

The meaning of modes of vibration are discussed for elastic bodies submerged in an infinite acoustic fluid. In particular, it is shown that a submerged body has more modes than does the same body in vacuo, that the individual modes of the fluid/solid system correspond generally to perturbations of either ``fluid'' modes or ``solid'' modes, and that the modes are not complete. Finally, it is shown that when the interaction between the wave types that comprise the different modes are strong, it may be impossible to identify a mode as originating with either the fluid or the solid. The results of this study have great general relevance, especially in the areas of statistical energy analysis (SEA), the singularity expansion method (SEM), and the resonance theory of scattering (RTS). [Work supported by ONR.]