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<p>Small unmanned surface vessels and underwater vehicles can adjust course in real time through the differential rotation of two symmetrical propellers arranged on both sides of their sterns. This study, which considers internal and external rotation scenarios, focuses on the acoustic characteristics of propellers during steering maneuvers achieved by differential rotation. A hydrodynamic flow field is simulated by using commercial CFD software, and noise is predicted through hybrid detached eddy simulation coupled with the Ffowcs Williams-Hawkings acoustic analogy. Simulation results reveal two distinct blade passing frequencies and two corresponding values of the advance coefficient <i>J</i>, both caused by the rotational speed disparity between the two propellers. For the starboard propeller, the advance coefficient <i>J</i> under differential rotation is higher than that under normal rotation, which leads to persistent twisted hub vortices without instability. Furthermore, the vortex twisting region extends over a long distance. At equivalent downstream positions, interaction between vortices generates strong pressure fluctuations and increases radiated noise in the surrounding flow. When the noise frequency is below 500 Hz, the average downstream noise level under differential rotation is 15 dB higher than that under normal rotation. During straight-line sailing, the noise level of the full band at the monitoring point under internal rotation is 7 dB higher than that under external rotation.</p>

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Numerical Investigation of Ship Radiated Noise Induced by Twin Propellers Under Differential Speed Constraints

  • 期刊论文

  • 发表日期：

    2025年9月19日

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  • Quanzhong Ji,
  • Chunlong Huang,
  • Liang Zhang,
  • Ran Cao,
  • Feng Zhang

摘要

Small unmanned surface vessels and underwater vehicles can adjust course in real time through the differential rotation of two symmetrical propellers arranged on both sides of their sterns. This study, which considers internal and external rotation scenarios, focuses on the acoustic characteristics of propellers during steering maneuvers achieved by differential rotation. A hydrodynamic flow field is simulated by using commercial CFD software, and noise is predicted through hybrid detached eddy simulation coupled with the Ffowcs Williams-Hawkings acoustic analogy. Simulation results reveal two distinct blade passing frequencies and two corresponding values of the advance coefficient J, both caused by the rotational speed disparity between the two propellers. For the starboard propeller, the advance coefficient J under differential rotation is higher than that under normal rotation, which leads to persistent twisted hub vortices without instability. Furthermore, the vortex twisting region extends over a long distance. At equivalent downstream positions, interaction between vortices generates strong pressure fluctuations and increases radiated noise in the surrounding flow. When the noise frequency is below 500 Hz, the average downstream noise level under differential rotation is 15 dB higher than that under normal rotation. During straight-line sailing, the noise level of the full band at the monitoring point under internal rotation is 7 dB higher than that under external rotation.