Study On Noise And Vibration Of Underwater Cabin And Effects Of Composite Foundation Of It

The vibration noise performance of ships is getting more and more attention at present.Long time vibration, especially the resonance, can easily damage the structure of the ship and equipments. The vibration and noise in the cabins and working area has greatly affected the comfortableness. It will make people feel tired and irritable or even lead to permanent injury to staff is staying in such working environment for a long time. In the military confrontation, the impact of noise and vibration on radar and sonar is huge. The size of the underwater acoustic radiation will directly affect the scope of the investigation for both parties. So it needs to pay special attention to the vibration and noise performance of the ship during the manufacturing of the ship. The composite material is a new kind of material with good mechanical properties, shock absorption, impact resistance, fatigue resistance,high specific strength and modulus and good design. It has important practical significance to apply the composite material to the vibration-isolating shipboard foundation to improve the ship vibration reduction technology,since it has these characteristics.This paper takes the underwater cabin with the foundation structure as research object.Firstly, using the finite element method for modal analysis and frequency response analysis of cabin with on water; At the same time, studying the vibration characteristics of the structure of the cabin with different thickness water based on fluid-solid coupling and finite element method; And, analysing the vibration characteristics of the structure of cabin in unbounded water by the infinite element method; And comparing and studing the above calculation results. Then, by self program writed of Fortran and Python language, using numerical method for solving the cabin on the far field sound radiation based on boundary element method and the Helmholtz integral equation, and the calculated results were compared with that of the research results from actran simulation software. Finally,establishing the cabin finite element model of composite foundation based on the classical laminated plate theory, and study on the vibration characteristics with different applications of composite laminates and different thickness of composite laminates, and comparing the vibration condition with the previous results.Through the above work, the following conclusions are obtained:(1) After the additional water layer, the vibration of the structure of the cabin is decreased to a certain extent, and the degree of reduction is related to the thickness of the layer; The calculated results are in agreement with the finite and infinite layers; Thevibration calculation in the unbounded water area is more real, but the computing efficiency is low. The calculation results of the 0.4m water layer are closest to the infinite water layer.(2) Radiation in the far field acoustic of underwater cabin increased in 0~100Hz, to stabilize after 100Hz; The program calculation results are consistent with the simulation results in the error tolerance range, and the self compiled boundary element program is feasible.(3) Composite foundation for cabin is good for vibration suppression; The application of the composite material in the foundation panel is the most favorable to the vibration reduction, and the effect of application of the composite material in the whole base is the worst; When the composite is applied in the panel plate of the foundation, the optimal thickness ratio of the composite material boundary layer and the sandwich layer is 2:1, and the best thickness ratio of the composite material boundary layer and the sandwich layer is1:1 when the composite is used in web and elbow plate of the foundation.