Fast prediction of the long-range structural acoustic radiation in the stratified ocean

Abstract

In this study, we propose an efficient method for predicting three-dimensional acoustic radiation from arbitrary structures immersed in a shallow-water waveguide. By incorporating the finite element method (FEM) and the wave superposition method (WSM), the detailed acoustic radiation from the vibrating structure in the near field is calculated by numerically evaluating the source strength integral that represents the Helmholtz exterior problem. Transitioning to the far-field region, where the structural acoustic radiation is characterized by the source directionality, an analytical, normal-mode expression for the source-strength integral is derived, representing the structural acoustic radiation as a sum over propagating eigenmodes, with the modal excitation determined by the directionality of the acoustic radiation mode. This represents a significant improvement in numerical efficiency by reducing computational complexity, especially for high-frequency and long-range predictions. The critical distance distinguishing the near-field and far-field regions is discussed in detail, determined by the horizontal wavenumber and structure size. Numerical simulations demonstrate the effectiveness of the proposed method and reveal the coupling mechanism between the structural acoustic radiation and the underwater acoustic propagation. The proposed method is adaptable to optimize the passive sonar performance by achieving the real-time prediction of the structural acoustic radiation in realistic ocean-acoustic environments.

Recommended citation: R. Nie, T. He, J. Fan, K, Zhao and B. Wang, Fast prediction of the long-range structural acoustic radiation in the stratified ocean, Ocean Eng., 314 Part 1: 119673 (2024) (https://doi.org/10.1016/j.oceaneng.2024.119673)
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