Acoustic reflection and refraction caused by the ocean channel pose challenges to the stable underwater propagation and application of acoustic vortices. This paper focuses on the propagation mechanisms and effective identification of acoustic vortices in marine environments. The proposed Gaussian beam-based parallel computing and least squares (LS) channel equalization methods improve computational efficiency and topological charge identification accuracy. First, we theoretically reveal that the spacing of acoustic vortex phase interference fringes in free space depends on the frequency-to-propagation distance ratio. Subsequently, the interference patterns of acoustic vortices with opposite topological charges caused by surface reflection are investigated. Shallow sources suffer more severe interference and mode crosstalk, while deep sources exhibit denser horizontal fringes but typically maintain higher mode purity. Furthermore, using parallel Gaussian beam simulations, we find that refraction contracts the vortex in depth and enables stable propagation over certain distances in deep-sea sound channels, but subsequently causes beam convergence that creates high-energy zones overwhelming the vortex structure. To address this, a LS channel equalization method is presented to effectively mitigate multipath interference and improve identification accuracy. Finally, scaled water tank experiments in free-space and half-space environments validate the propagation mechanisms and confirm that the proposed algorithm enhances topological charge purity. This study reveals the underwater propagation mechanisms of acoustic vortices and provides a reference for the reliable deployment of underwater acoustic systems based on orbital angular momentum.
Guo et al. (Wed,) studied this question.