Objectives Arousing the "Jellyfish mode" of a propeller can lead to strong low-frequency, narrow band sound radiation. On this basis, the second sound radiation mechanism of the "Jellyfish mode" has been investigated. The propeller excitation force, amplified by the elasticity of the propeller and shaft, is transmitted to the hull and results in the axial vibration and sound radiation of the hull, which is known as the "Jellyfish effect" of a submarine.
Methods The direct acoustic radiation analysis model of the propeller is built based on the noise source equivalent method, and the FEM/BEM coupling method is utilized to analyze the vibration and sound radiation characteristics of the propeller-shaft-hull coupling system.
Results The analysis results show that the superposition of the sound radiation induced by the "Jellyfish mode" of the propeller will be significantly enhanced. The propeller excitation force transmission will be amplified when the "Jellyfish mode" of the propeller is aroused, and the axial vibration and sound radiation of the propeller-shaft-hull coupling system will increase significantly, to become an extremely significant sound radiation signature; there is also a relation between the repetition frequency mode of the propeller and lateral propeller excitation force.
Conclusions The study revealed the concept and sound radiation mechanism of the "Jellyfish effect" of a submarine. The research above can provide theoretical support for quiet propeller design and propulsion system noise control, which are of great significance to both the theory and practical engineering.
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