An Investigation On Prediction Method And Characteristics For Vibro-acoustic Of Complex Underwater Structure

For the vibro-acoustic prediction of complex underwater structure, the methodcombining of finite element method and boundary element method (FEM/BEM) is used tolow frequency analysis, and the statistical energy analysis method (SEA) is used to highfrequency analysis. But two problems exist: one is the low computing efficiency ofFEM/BEM; secondly, the reduction of computing efficiency using the finite element methodand SEA can’t meet the accuracy solution in “intermediate frequency”. This paper aims atovercome these two limitations of present method. The investigation on full-bandvibro-acoustic prediction methods and characteristics of underwater structure based on theoriginal numerical methods is conducted.The issue of fluid-structure interaction can’t be applied conventionally while there werefluid on both sides of double cylindrical shell was as the first investigation in this paper.Regarding to the disadvantage of large-scale calculation and low-solving efficiency whenusing FEM/BEM, the methods of perfectly matched layer (PML) and Automatically MatchedLayer (AML) developed in recent years were put forward, The numerical results of theexample show that a good agreement can be obtained by using the FEM/BEM、PML andAML method; For the simple structures with small size, high solution efficiency can beobtained by using the AML method, however, the FEM/BEM has a higher efficiency forcomplex structures with huge size.Using SEA method to predict the vibro-acoustic of underwater structures withhigh-frequency excitation, detailed studied on the determine of model parameters、thedivision of subsystems and the accuracy of the results were related in the paper. Studies haveshown that SEA results are not accurate when the modal number of subsystems doesn’t meetdemand（This means the frequency isn’t high enough.）, so we need to seek other solutions.Due to the limitations of predicting structural vibro-acoustic while using the finiteelement and SEA method, in this paper, presented a hybrid FE-SEA method by combiningtwo methods above, and verified the intermediate-frequency feasibility of this hybrid methodthrough the calculation of acoustic radiation of underwater structure.The paper looked at the example of underwater ring-stiffened cylindrical double-shell, investigated the main effects of external heavy fluid and connection form of inner-shell andouter-shell (Fluid between the shells and horizontal stiffeners) on the low-frequencystructural vibration and acoustic radiation by using the AML method.Regarding to stern cabin of a typical complex underwater structure, studied on its low-intermediate-frequency vibro-acoustic characteristics under different working conditions byusing FEM/BEM, studies have shown that the power of vibration and acoustic radiation byasymmetrically central excitation is larger than symmetrically dispersed excitation, fluidbetween two shells mitigates the vibration of outer shell to certain extent, but increases theacoustic radiation; then, investigated the intermediate-frequency acoustic radiationcharacteristics of this structure by using the hybrid FE-SEA method.