Sound Radiation Analysis Of Ribbed Cylindrical Shells With Viscoelastic Layer And Noise Characteristics Analysis

With the continuous development of the underwater-acoustic countermeasure, the power is consumedly strengthened for sonar to identify and track underwater targets. How enhance the concealment performance of submarine more effectively, have become contemporary navy to equip an important topic which needs solve urgently to in the technique. Finite cylindrical shells are the main structures of the pressure and non-pressure hull of submarine. To coat with viscoelastic layer on the hull of submarine is one of the main methods of vibration contral noise reduction. It is significant for noise reduction to study the viscoelastic characteristics of covered cylindrical shell immersed in fluid.In this paper, the vibroacoustic characteristics of covered ribbed cylindrical shells driven by a harmonious point force are studied. The shell is simply supported and its displacements is expanded in a series of the in-vacuo modes. The shell motion is described by Flugge thin shell theory. Make use of modal expansion method to expand displacement of the shell according to the double series form. Suppose a damping layer thickness with the ratio of its stretch and shrink wave-length far small in 1, along the thickness direction, displacement of damping layer make use of approximately Taylor expandedness to solve the Navier square. The harmonic pressure can be expressed by using the well known harmonic Green's function for the exterior Neumann boundary value problem, and be solved by boundary conditions of the shell surface to obtain the pressure expression. Lastly, the coupling vibration equation of the acoustic fluid-structure is gotten. Through the border conditions of damping layer combined with the shell the coupled oscillation equation was solve, and radiation sound field expression was shown using the shell displacements. After solving the coupling equation, two parameters, which indicate the general characteristics of the shell vibration and sound radiation are calculated. The parameters are the acoustic radiated power level and the radial quadratic velocity level. The focus of the numerical calculation is the analysis of the difference of acoustic radiated performance between different damping parameters. The discussion is favorable...