Numerical study on propeller hydrodynamic excitation influenced by torsional vibration of shaft system

Abstract

Torsional vibration of the propulsion shaft system has a significant influence on the safety and stability of marine navigation. Additionally, the resulting instantaneous fluctuation of rotational speed affects the hydrodynamic loading of propeller. To investigate this influence, a numerical model of propeller hydrodynamics influenced by hull wake and torsional vibration is established using delayed detached eddy simulation. First, the modeling method is described, and the model is verified and validated. Second, simulations are carried out for different amplitudes and frequencies of torsional vibration, and the hydrodynamic excitation, pressure pulsations and flow field features are analyzed detailly. The results show that torsional vibration significantly affects the hydrodynamic excitation of propeller, due to the fluctuations in blade section velocity, angle of attack and loading induced by instantaneous rotational speed, which can be equivalent to non-negligible added mass and damping. Through statistical analysis of the temporal-spatial pressure distribution, the complex modulation of torsional vibrations with different frequencies on the flow field from macroscopic hydrodynamic excitation to microscopic flow features is revealed. The effect of fluctuating small-amplitude loading on the dynamics and stability of propeller wake is also studied. This study provides theoretical support for designing and optimizing marine propellers and propulsion shaft systems.