The Research For Temporal-Frequency Prediction Method Of Medium-low Frequency Line Spectrum Vibration And Noise Of Ship

With the rapid development of the economy and technology, the international trade has become more and more frequent and the transportation instruments, such as airplane, ship tend to larger, which the size of the installations is bigger. From this, the problem of structural vibration and noise has become more serious. Therefore, how to realize the accurate and efficient analysis of the dynamic response of large complicated ship, especially the dynamic prediction of medium-low line spectrum of vibration and noise, is in the urgent need of being solved in engineering applications.Therefore,this paper states the development of the analytical prediction method on vibration and noise of ship. The shortcomings and deficiencies on dynamic response prediction are analyzed. The result shows that numerical prediction method can realize the prediction of vibration and noise in calculated frequency, but the modal superposition is mostly adopted. The single analysis only can realize the dynamic prediction of single frequency point. The calculation efficiency is low and the prediction precision is inaccurate.To overcome the above problem, the paper establishes the temporal-frequency comprehensive prediction method of line-spectrum vibration and noise in ship structure,which combined the time-domain analysis method with the frequency-domain model superposition method. First, this paper stated the basic theory of temporal-frequency prediction method of line spectrum vibration and noise in ship structure. The precision and efficiency of time-domain and frequency-domain are contrasted by using numerical example.This paper discussed the temporal-frequency load analysis method in prediction of vibration and noise, the temporal-frequency model sharing method and the method of numerical analysis on dynamic response. The analysis method of temporal-frequency load contains two parts in time-domain and frequency-domain. The relationship of the time increment of time-domain load and the frequency upper bound of frequency-domain load, the time scale of time-domain load and the frequency resolution ratio of frequency-domain load were studied.For the situation of equipment dynamic parameters locally unknown and under-chassis vibration acceleration given, the impedance analysis method is deduced and proposed to solve the ship dynamic response analysis. The validity of the method is verified with the ship compartment and the effects of different under-chassis load ways are investigated. Then, the model sharing method of time-domain and frequency-domain in prediction of vibration and noise is studied. The principle and method of simplifying ship model and flow field model is analyzed. The transformation method of the results of time-domain and frequency-domain is studied.On this basis, this paper summarized and established the systematization method of temporal-frequency prediction of medium-low line spectrum vibration and noise of ship structure. And the efficiency of numerical calculation is improved by using the temporal prediction method with the single analysis. The frequency resolution of prediction results is also enhanced. With the frequency-domain model superposition method,the analysis of key frequency and the major transfer approach of vibration and noise can be realized. So the prediction precision and efficiency are verified by using the numerical model. The effectiveness of the temporal-frequency prediction method of medium-low line spectrum vibration and noise of ship structure are preliminary verified by using the structure of stiffened cylinder shell. This can provide a basis for the quantify prediction and study of vibration and noise of ship.In the end, the characteristics and laws of the vibration and noise distribution of ship are studied by using temporal-frequency prediction method of medium-low line spectrum vibration and noise, which provides the reference for analyzing the structural vibration and underwater acoustic radiation of real ship.