Underwater radiated noise characteristics: A comparative study of immersed and traditional waterjet propulsion systems.

The immersed waterjet propulsion method represents an innovative advancement in traditional waterjet propulsion technologies. Unlike previous studies that primarily rely on fluid-induced acoustics theories, such as the Lighthill's equations, this research experimentally validates key parameters affecting radiated noise levels, including jet velocity and nozzle pressure, providing new insights into noise reduction mechanisms in immersed waterjet systems. Through a comparative analysis of noise emission profiles, this study demonstrates that immersed waterjet devices exhibit a substantial reduction in underwater radiated noise, particularly within the critical low-frequency range of 1 to 5 kHz, where the noise reduction is most pronounced. By conducting controlled experimental assessments, this research contributes to a more comprehensive understanding of the underlying acoustic features and their influencing factors. Additionally, the study contextualizes its findings within the broader scope of naval propulsion systems, highlighting how immersed waterjet propulsion can significantly enhance stealth capabilities. The key contributions of this study lie in its detailed characterization of radiated noise mechanisms and its provision of empirical evidence that extends beyond theoretical predictions. The results of this study bridge a crucial gap in the literature by offering experimental insights into the radiated noise characteristics of immersed waterjet propulsion, a topic that has been less explored due to operational and technical challenges. Specifically, the immersed waterjet propulsion system demonstrated a reduction in underwater radiated noise by up to 12 dB in the 1 to 5 kHz frequency range compared to traditional stern-type systems under identical conditions. These findings lay a strong foundation for further optimization and application of immersed waterjet propulsion systems in modern naval and commercial vessels.