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Contra-rotating propellers (CRPs) are widely used in different kinds of underwater vessels, owing to their excellent stability, propulsive efficiency, and balanced torque distribution characteristics. However, the cavitation that occurs due to their high rotational speeds also generates high levels of cavitation noise. In this study, CRP noise radiations were predicted via detached-eddy simulations with the shear stress transfer k-ω turbulence model, the Ffowcs Williams–Hawkings (FW–H) acoustics model, and the Schnerr–Sauer cavitation model. The cavitation noise of the CRP was predicted using sound radiation theory for spherical bubbles and compared to non-cavitation noise levels from the FW–H equation. It was found that the non-cavitation noise of the CRP is significantly louder in the axial direction than in the radial direction. Furthermore, the noise sound-pressure levels (SPLs) of the flow field generally decrease with increasing frequency. When the effects of cavitation on the flow are taken into account, the SPLs of the CRP noise become significantly higher at all equidistant positions from the center of the propeller. The anisotropy in sound pressure also becomes insignificant when cavitation is present.

Severe wake-structure interaction induces intense vibrations and noises. In this study, the rudder is simplified into a plate fixed at two ends. The vibrations of the plate operating in the propeller wake are analyzed. Detached eddy simulation is employed to simulate the turbulence in the flow field and propeller wake. The structural deformation equation is solved via the finite volume method. The pressure fluctuations in the propeller wake and the vibrations on the plate are investigated. The results show that the excited vibrations coexist with natural vibrations on the plate. The natural vibration mode can be occupied by the excited vibration. The lock-in regime between the excited vibrations and natural vibrations leads to weaker vibration at excitation frequencies. The vibration mode induced by the hub vortex transfers to the first natural vibration mode when the shaft frequency approaches the first natural frequency. The vibrations on the plate are more dominant at the first natural frequency in the approach of the shaft frequency to the first natural frequency. This investigation of plate vibrations induced by the propeller wake contributes to the structural design of the ship.

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