Research On The Measurement And Analysis Method For Mechanical Noise Source Of Vessel Moored In The Dock

Acoustic stealth is one of the most important factors to judge the operational performance of vessel.It's significant o carry on vibration attenuation and noise reduction for vessel.To carry on vibration attenuation and noise reduction and provide scientific basis for the decomposition of noise index in the process of vessel's acoustic design,actualizing acoustic stealth of vessel measurement and evaluation in the dock is an important measurement stage.However,carrying on noise source measurement and analysis in dock is severely challenged by complicated acoustic environment.The existing conventional and high-resolution noise source localization method can't localize and identify noise source effectively.It's important to utilize acoustic field information of dock condition to carry on noise source localization and identification technique research,so the major noise source can be found and the contribution rate of noise sources towards acoustic field can be determined.Mechanical noise source is the major noise source of vessel which is under the condition of cruising.This paper develops the measurement and analysis method for mechanical noise source of vessel which moores in the dock,including nearfield localization method for mechanical noise source and mechanical noise source separation and quantification method.This paper aims at expounding mechanical structure vibration and noise transmission property under the condition of dock,and carrying on research from two respects including theory and experiment.The main research content includes several respects below:1.This paper begins with the simple model of signal which is received by array in nearfield under free field condition,MVDR based on amplitude compensation,robust noise source localization algorithm and the localization algorithm based on compressive sensing(CS)are researched.To solve wideband source localization problem,coherent signal-subspace method is researched.Further,aiming at noise source localization in nearfield for the condition of dock,nearfield measurement model of noise source in dock can be constructed.The expression of acoustic field under dock condition is derived based on ray theory.Passive time reversal mirror can focus noise in time and spatial domain under multipath condition.Passive time reversal mirror and nearfield high-resolution localization method are combined,and nearfield high-resolution localization method based on passive time reversal mirror is researched.This algorithm uses multiple path information fully,and it can achieve noise source localization under dock condition effectively.Then,vector signal processing is brought into nearfield high-resolution localization method based on passive time reversal mirror,andlocalization performance is improved using combination array which is composed by vector elements and pressure elements.To get robust localization result,worst-case performance optimization is applied into nearfield high-resolution localization method based on passive time reversal mirror.To solve wideband source localization problem,coherent signal-subspace method is combined with passive time reversed localization method,and wideband noise source is localized robust in dock.Owing to the spatial sparsity of noise source,localization system in the condition of dock is established in the theoretical framework of CS,passive time reversed localization method based on CS is proposed.Because the scale of mechanical noise source is large in the range of low frequency,localization method based CS is effective in the range of high frequency.To validate the effectiveness of the proposed method,experiment of noise source localization is developed.2.According to localization result of mechanical noise source and vibration energy distribution result of the surface of shell structure,radiation region of the surface of shell can be determined.Prior information can be provided for noise source separation and quantification.This paper proposes network hierarchy diagnosis to solve the identification of noise source for underwater complex structure based on analytic hierarchy process and partial coherency analysis.Based on vibration and noise transmission property of vessel mechanical structure,network hierarchy diagnosis system is divided into internal structure vibration system and external acoustic radiation system.Therefore,measurement points of mechanical equipments,shell structure and underwater acoustic field form network hierarchy diagnosis system.The contribution rate of mechanical equipment toward acoustic field can be determined by fusion calculation of the identification result of internal structure vibration system and external acoustic radiation system.Hierarchy diagnosis utilizes partial coherence analysis to solve identification problem of coupling mechanical noise source.Original scale is improved based on the enegy superposition in acoustic field,and the improved scale can quantificate the element of judgement matrix.3.To validate the effectiveness of noise source localization and identification method,localization and identification experimental research of cabin model mechanical noise source is carried on in reverberation tank.The engineering practical property of localization and identification algorithm proposed in this paper is testified by the cabin model experiment,and it has guiding significance and engineering applicable value to vessel measurement.