The effect of finite wind fetch on the acoustic field scattered from wind‐driven sea surfaces

Abstract

The effect of a finite fetch on the acoustic field scattered by the ocean wind‐driven surface for various wind speeds is analyzed through numerical simulation. The JONSWAP spectrum is adopted to describe the surface statistics of growing seas and the Pierson‐Moskowitz spectrum for fully developed seas. Ensembles of three‐dimensional surfaces having the desired directional spectra are numerically generated. For each surface realization, the complex pressure of the forward scattered field is calculated within the framework of the Helmholtz‐Kirchhoff theory for kr > 1. Statistical moments of the scattered field are then calculated as ensemble averages. The fields scattered in the windward and cross‐wind directions are evaluted for frequencies up to 1.5 kHz and for angles away from grazing incidence. Results indicate that the scattered field is sensitive to the difference between the JONSWAP and the Pierson‐Moskowitz spectra. In particular, the total intensity and the coherence of the scattered field are sign...