HYBRID RAY-MODE ANALYSIS OF ACOUSTIC SCATTERING FROM A FINITE, FLUID-LOADED PLATE

In this paper we develop a hybrid ray-mode algorithm to model the acoustic scattering from a finite, fluid-loaded thin elastic plate excited by a time-harmonic line pressure force exterior to the plate. Emphasizing the mid-frequency regime where internal structural wave phenomena are important, the problem is formulated in terms of a self-consistent system parameterization based on the ray-mode phenomenology in a generalized version of the geometrical theory of diffraction (GTD). The GTD constituents involve specularly reflected, transmitted and edge-diffracted exterior ray fields, as well as subsonic and supersonic traveling and resonant internal mode fields, with exterior-interior coupling taking place through phase matching along the smooth portions of the plate and through the edges. The amplitudes of these GTD wavefields are determined by excitation, conversion and coupling coefficients, some of which can be extracted in analytical form from the canonical infinite plate geometry. Since the ray acoustic algorithm for a complex system is built around the interaction between localized events on constituent simpler canonical systems, a short-pulse-excited time domain (TD) reference base with its space-time resolved output response is convenient for sorting out the ray-mode phenomenology. This route is followed here for the finite plate, for which numerical TD reference data is furnished by a finite-difference time domain (FDTD) code. We confirm, either directly or via data processing, that all observed wave effects are accounted for in our frequency domain hybrid ray-mode algorithm. Extension into a TD wavefront-resonance algorithm is under consideration.