Study On Wave Form Transformation Analysis Method Of Elastic Wave In Ship Hull Space Grillage Structure

Hull structure is a complex space structure coupled by a large number of space plates and frames,including deck,bulkhead,side outer plate and double bottom plate frame.The excitation generated by the hull equipment propagates in the grillage structure in the form of elastic wave,causing the dynamic response of the hull structure,and finally transforming into underwater radiated noise,which affects the normal operation of the ship.In this paper,based on the vibration and noise reduction of surface ships,aiming at typical space grillage structure of ship structure,the transmission and conversion characteristics of elastic wave in grillage structure of ship are studied.This paper analyzes the mechanism of vibration energy transfer in ship structure and puts forward some suggestions on the evaluation and optimization design of ship structure dynamics characteristics.The main research contents of this paper are as follows.First in this paper,a wave analysis method based on spectral element method is proposed,the hull space plate structure is equivalent to the beam structure model by using the modal equivalence method,and the wave transformation phenomenon at the coupling point is characterized by the energy density of elastic wave,so as to obtain the waveform conversion characteristics and law of elastic wave in the hull space plate structure.Then for the bottom-bulkhead-deck space grillage structure in the midship of a ship,bottom-side-deck space grillage structure and the side-deck-side space grillage structure of aft engine room,the elastic wave transmission characteristics are respectively equivalent to the cross-linked U-type coupling beam,the angle U-type coupling beam and the angle Y-type coupling beam.When one end of the hull structure is excited by harmonic axial force and vertical force,the elastic wave energy density in the equivalent model is analyzed and the elastic wave energy transfer coefficient in the model is calculated,then the transmission characteristics of incident longitudinal wave and bending wave in the hull space slab structure and the waveform conversion law at the coupling point are obtained.With finite length grillage structure in the coupling grillage structure as the research object,the influence of physical parameters of hull grillage structure such as damping coefficient,coupling angle between panel frame structures and length,thickness and density of grillage structure on elastic wave transmission characteristics is analyzed,and the influence of physical parameters of bulkhead,bulkhead and deck frame on elastic wave transmission is obtained.Finally the waveform conversion validation test of cabin model is carried out,and a typical ship cabin scale model is established according to the actual ship engine room and cabin structure.The natural frequency of each grillage structure in the cabin is calculated,the vibration acceleration at each measuring point of the typical ship cabin scale model is measured by sensors,the energy density of each grillage structure is calculated,and the energy transfer coefficient of each grillage structure is obtained,which verifies the accuracy of the method based on spectral element method to solve the elastic wave transformation characteristics of hull grillage structures.