Noise characteristics of open toroidal propeller over a wide speed range

The acoustic performance of underwater propulsion devices is the core requirement for the noise reduction design of maritime vehicles. Traditional propellers are prone to generating high-intensity discrete tonal noise and broadband noise under different rotational speeds and cavitation conditions, with prominent tip vortex cavitation. Based on Delayed Detached Eddy Simulation (DDES) and the permeable FW-H acoustic equation, the flow and noise evolution of the open toroidal propeller under low-speed non-cavitating and high-speed cavitating conditions are systematically analyzed and validated. Under non-cavitating conditions, the overall sound pressure level (OASPL) is reduced by approximately 3.8 dB and discrete tonal energy by 35% compared with the traditional propeller. Directivity analysis shows the maximum noise reduction of 4.0 dB appears at 0° and 180°.Under cavitating conditions, the toroidal configuration suppresses tip vortex cavitation and radial flow, exhibiting superior mid-to-high frequency broadband noise performance. The quadrupole component dominates the total acoustic energy under cavitating conditions, confirming that volumetric sources are the primary contributors to cavitation noise. Propagation analysis reveals that the toroidal propeller has a higher attenuation coefficient within the investigated region, indicating a faster sound pressure decay in this region.