Analysis of Ship Propulsion Shafting Vibration Using Coupled Torsional-Bending Model

Abstract

The paper describes a coupled torsional-bending model of ship propulsion system vibrations. The developed model is based on the modified model of the Jeffcott rotor. In order to test the model and determine the coupled torsional-bending vibrations, several cases were analyzed. First, a reference case corresponding to a fully axisymmetric ship propulsion system is set up. Then, the influence of the constant radial force in the vertical direction at the position of the stern bearing was analyzed, such as the conditions of navigation of the ship at calm sea under partial or fully loaded hull. Finally, the case of sailing on rough sea is analyzed, when the propeller racing occurs due to the stern lifting out of the sea. For simplicity, the harmonic law of amplitude changing of the vertical radial force on the stern tube bearing as well as of the propeller load was adopted. Based on the results of numerical analysis, it was found that the proposed model well describes the case of coupling of torsional and bending vibrations of the propulsion system.

Study on the influence of vibration characteristics of ship’s stern structure

“…Pang et al [1] analyzed the ship's vibration model under propeller excitation, discovering that vibration noise is mainly induced by lateral excitation forces, and their amplitude is significantly correlated with the hull thickness. Marijančević et al [2] conducted studies in different sea conditions, finding that the degree of torsional coupling in the propulsion system increases with the growth of lateral forces. Hua et al [3] suggested that the research on the control methods for the transverse vibration of the propeller shaft system is still incomplete, and the current understanding of the impact of design parameters in the stern structure on vibration control is insufficient.…”