Dynamics Of Ship Propeller-Shaft Systems Considering Oblique Flow And Whirl Effect

Vibration noise produced by propeller shaft system is one of the main sources of vibration noise.The propeller usually works in the inhomogeneous incoming flow whose direction is uncertain.At the same time,due to eccentricity and assembly errors,propeller shafting generates whirl vibration,which leads to complicated propeller motion trajectory and influences the vibration and noise characteristics of propeller hydrodynamics and propeller shaft system.In order to effectively reduce the low frequency vibration noise of ships,it is urgent to explore the generation mechanism of vibration noise of propeller shaft system and the related change law.Based on the coupling relationship between the medium of flow field,propeller and shafting,this paper studies the influence of oblique flow and cyclotron effect on propeller hydrodynamic force and the influence of unbalanced excitation and fluid excitation on shafting vibration response under the condition of non-uniform incoming flow,and explores the interaction law between propeller hydrodynamic force and shafting vibration response on this basis.The main research contents of this paper include:(1)Based on the CFD method,the steady hydrodynamic characteristics of the sevenblade propeller with large oblique side are calculated,and the correctness of the basin model and the calculation method of steady hydrodynamic is verified by comparing with the experiment.(2)Based on the calculation of steady hydrodynamic characteristics,the influence of oblique flow Angle and whirl effect on unsteady hydrodynamic characteristics of propeller under the condition of non-uniform incoming flow is studied.The results show that oblique flow can significantly increase the direct flow rate of propeller under radial excitation.The whirl effect affects the axial frequency component of radial excitation.(3)The finite element model of the propeller shaft system was established by using the finite element method,and the vibration response of the propeller shaft system was analyzed based on the finite element method.The results were compared with the test results,and the correctness of solving the vibration response under the combined action of unbalanced excitation and flow field excitation was verified.(4)In order to solve the problem of fluid-structure coupling dynamics of oar-shaft system,a method of periodic iteration of flow field and structure field is proposed in this paper,and the interaction law between propeller hydrodynamic force and shafting vibration response is investigated by using this method.The results show that when the flexibility of the stern shaft section is large or the initial vibration response is large,the interaction between the propeller hydrodynamic force and the vibration response of the shafting should be considered,otherwise some error will be brought.