Analysis of the Influence of Target Internal Structural Load on Low-Frequency Acoustic Scattering

In this paper, the acoustic scattering characteristics of elastic shells subjected to internal structural loads are investigated. The normalized scattering morphology function and acoustic target strength of three elastic shell configurations—the spherical shell, the short cylindrical shell, and the Benchmark single-layer shell—were computed using the finite element–boundary element (FE-BE) coupled method, both before and after the addition of internal plating and structural loads. By comparing the monostatic (forward-incidence) and bistatic (broadside-incidence) acoustic scattering responses—including co-polarized and cross-polarized components—of identical targets with differing internal configurations, the influence of internal plating and structural loads on low-frequency acoustic scattering characteristics was analyzed. Results show that: (1) the lower the height of the internal deck relative to the bottom of the shell, the weaker its influence on the resonant scattering characteristics; conversely, as deck height increases, the frequency of the first low-frequency resonance peak shifts toward higher frequencies; (2) when the length of a single structural load does not exceed one wavelength at 1 kHz, its effect on the low-frequency resonant scattering characteristics is negligible after being mounted on the deck—thus permitting simplification of the structural model in numerical simulations; (3) under both forward- and broadside-incidence conditions, the effect of a multi-load configuration on low-frequency acoustic scattering can be effectively approximated by that of an equivalent single-load structure whose total length equals the summed lengths of all individual loads.