Vibro-acoustic Characteristics Calculation Of Acoustic Excitation Immersed Structures

Structural vibration has always been the focus in Engineering.As for the submerged structures,such as ships and submarines,the problems of underwater acoustic radiation should also be paid attention to.Underwater acoustic radiation problem is a typical problem of fluid structure interaction,which is based on the characteristics of structure and fluid.In order to solve complex engineering problems,scholars have created a variety of numerical methods solving the problem of fluid structure interaction.The finite element method is always used to model the structure.The finite element method and boundary element method are the main methods for modeling the fluid.The fluid finite element method is convenient to be coupled with the structural finite element,which is suitable to solve the fluid solid coupling problem in finite space.The boundary element method has an advantage over the infinite domain comparing to the finite element method.The boundary element method is used in this paper.The main contents of this paper are as follows:First of all,the shell structure is simplified the model of Mindlin plate and membrane considering strain produced by shear.Based on the finite element method,the finite element equation is derived by using the four nodes quadrilateral isoparametric element.The program is programmed and the correctness of the program is verified by the modal calculation of the simply supported plate and the two ends fixed cylinder shell.Then,based on the Helmholtz equation,the boundary integral equation is derived by the method of weighted function.On the boundary,the four node isoparametric element.The coordinate transformation method and CHIEF method are used to solve the problem of singular integral and the non uniqueness problem at the characteristic frequency respectively.The boundary element method is used to calculate the acoustic radiation and acoustic radiation for a given boundary condition pulsating sphere.Finally,for the finite element and boundary element equations,the paper deduces the structure vibration equation and acoustic radiation equation by coupling the continuity condition equation.And the program is programmed to calculate the fluid solid coupling vibration and sound radiation solutions.For the cylindrical shell with internal acoustic excitation,the acoustic sound pressure level is calculated using Green function method.The pressure on the boundary will be loaded onto the cylindrical shell.The paper gives the calculation results of vibration and sound radiation of cylindrical shell under water with internal point source acoustic excitation in any position.