| With the implementation of the marine engineering equipment and high technology ships,one of ten key areas of the “Made in China,2025”,an increasingly high demand for the comfort and stealth performance of high technology ships is proposed.It requires having a thorough understanding of overall noise level and then seeking for the corresponding active control strategies in the initial stage of ship design.So it’s of great engineering significance to study the strategy to predict the noise of surface vessel and conduct the active control.Moreover,with the rapid development of the computer technology,a large number of numerical simulation methods have been widely used in the preliminary design of practical engineering projects,which contributes to greatly shortening the design cycle and reducing the design cost.In this thesis,taking a certain type of escort ship as the research object and on the basis of existing numerical simulation methods,the strategies for predictions of the hydrodynamic noise,mechanical noise,self-noise in sonar platform area,underwater radiation noise and ship cabin noise are presented,and active noise control measures are introduced further.The main research contents are as follows:Firstly,the hydrodynamic noise,which is classified into the flow-induced noise and the noise from the flow-induced vibration,is studied.For the former,the general principle using the Boundary Element Method(BEM)to solve the turbulent field is derived;the numerical simulation for the flow-induced noise is conducted by the combination of Finite Element Method(FEM)and BEM,according to which,the noise distribution is analyzed.For the latter,the Statistical Energy Analysis(SEA)is employed to study its characteristics.The complete hydrodynamic noise is further obtained by the synthesis of the results of the above two noise components.Secondly,the strategy to predict the mechanical noise is investigated.To make the results more reliable,the coupled acoustic-structural analysis and SEA are adopted to separately predict the mechanical noise in medium-low frequency and in high frequency.The feasibility of two methods is also validated by comparison.In the analysis,all the vibration excitations generated by the shipboard equipment are taken into account.Besides,the main noise sources are analyzed,according to which active control measures are taken to reduce the mechanical noise level.Then turn the attention to the self-noise in the sonar platform.This analysis is also on the basis of SEA.The determination of the self-noise level in the sonar platform comprehensively considers the actions of turbulence fluctuation,mechanical excitation and propeller excitation.And the effects of the three kinds of excitations are also checked.In addition,the influence of the sound-absorption wedge on reducing the self-noise in the sonar platform is studied as well.Next,the underwater radiation noise is calculated by SEA.This part is realized based on the hydrodynamic noise and mechanical noise,and combined with the measured ship propeller noise.Similarly,the underwater radiation noise level of ship before and after acoustic protection are studied respectivelyLastly,the SEA is utilized to predict the ship cabin noise.Through preliminary analysis of the ship which implements the outfitting and preliminary acoustic protection,the cabins whose noise level is beyond the standard are determined.And then the main causes of over high noise level are investigated from the standpoint of the dominant transfer pathway.According to the analysis results,the corresponding acoustic protection measures are carried out.Based on the comprehensive analysis of the existing research contents,this thesis makes a research on the prediction strategy for the noise of the surface vessel and active control technology for the first time,which can provide the reliable numerical simulation methods for the determination of ship noise in the preliminary design of high technology ship,and meanwhile,can offer the guidance for the follow-up studies. |
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