Wedge Assemblage Method for 3-D Acoustic Scattering from Sea Surfaces: Comparisonwith a Helmholtz-Kirchhoff Method

摘要

In the past, the Wedge Assemblage (WA) or Facet Ensemble method has beensuccessfully benchmarked in a number of 1-D acoustic scattering studies. The method offers a unique description of the scattering process in the time domain, allowing for the separation of reflected (image contributions) and diffracted components of the scattered field. Recently, the WA approach has been generalized to handle 2-D anisotrophic surfaces. In this new approach, the scattering surface is decomposed into elemental finite wedges made up of triangular facets. The generalized WA method is used to model moderate grazing angle, forward scattering from 2-D, wind-driven sea surfaces (5.5, 8, 11 m/sec wind speeds). Comparisons with results obtained from a Helmholtz-Kirchhoff approach are made for the frequency range of 200 Hz to 10 kHz. In general, the two models compare qualitatively quite well over the entire frequency band of interest but there are many discrepancies in the details of the two frequency responses. A major finding predicted by the new WA model is that diffractions dominate image contributions (reflections) even for the case of specular scattering. Keywords: Acoustic scattering; Reverberation; Sea surfaces; Surface roughness; Reprints; Mathematical equations. (cp)