2019_programme: ACOUSTIC WAVE SCATTERING FROM DYNAMIC ROUGH SEA-SURFACES USING THE FINITE-DIFFERENCE TIME-DOMAIN METHOD AND PIERSON-MOSKOWITZ FREQUENCY SPECTRUM



  • Session: 17. Modeling techniques for underwater acoustic scattering and propagation
    Organiser(s): Gunderson Aaron, Isakson Marcia
  • Lecture: ACOUSTIC WAVE SCATTERING FROM DYNAMIC ROUGH SEA-SURFACES USING THE FINITE-DIFFERENCE TIME-DOMAIN METHOD AND PIERSON-MOSKOWITZ FREQUENCY SPECTRUM [invited]
    Paper ID: 948
    Author(s): Higgins Alex, Siderius Martin
    Presenter: Higgins Alex
    Presentation type: oral
    Abstract: Most models for underwater acoustic propagation typically assume the sea-surface to be either perfectly smooth or rough but “frozen” in time. Long duration transmissions on the order of tens of seconds are being considered for next-generation sonar. These types of signals improve target resolution and tracking. However, they can interact with the sea-surface at many different wave displacements during transmission. This violates the frozen surface assumption and causes anomalies in the received signal which introduce additional transmission losses and Doppler effects. Full wave propagation models can be used to better understand the mechanisms behind these anomalies. This understanding leads to better system design and enhanced performance without having to perform extensive at-sea experiments. In this paper, a finite-difference time-domain (FDTD) method is developed to model the impact of both roughness and motion of the sea-surface. The FDTD method is a full-wave numeric technique that allows an arbitrary function to define the boundary points within the computational space. Surface motion is accomplished by modifying these boundary points at each time step. The rough, time-evolving sea-surface is modeled using a Pierson-Moskowitz (PM) frequency spectrum, which is simple to implement and fully defined by wind speed and direction. Results from FDTD simulations of static rough sea-surfaces are compared to a previously established integral equation solution method to evaluate the validity of the approach. Agreement is also demonstrated for FDTD simulations of a dynamic rough sea-surface and a theoretic statistical model. [Work supported by the Office of Naval Research]
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  • Corresponding author: Mr Higgins Alex
    Affiliation: NEAR-Lab, Electrical and Computer Engineering Department, Portland State University
    Country: United States
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