Research On Vibro-acoustic Characteristics Of Immersed Structures Based On FEM/FEM

Coupled structure Finite Element Method/fluid Indirect Boundary Element Method is used to solve the vibro-acoustic problems of immersed structure. By writing the relevant programs by FORTRAN.First, based on the theories of elastic mechanics and FEM, calculating the derivation of element stiffness matrix and mass matrix of plate and membrane element; introducing Gauss integral method simply; discussing the methods of solving the generalized eigenvalue problem; introducing the shift method.Second, based on the Helmholtz equation, calculating the Helmholtz integral equation for FEM, using the hexahedron element to disperse the integral equation and describing the process of the discrete; deducing the equations of calculating the acoustic radiation and acoustic modal problems; the sphere and cavity examples prove the correct of the programs. Deducing the equations of calculating the vibration characteristics of immersed structures based on FEM/FEM; discussing the direction of the normal in the simple acoustic domain boundary; writing the programs to calculate the vibration characteristics of immersed cantilever plate, the results prove the correct of the method; deducing the equations of calculating the vibration characteristics of immersed structures in complex acoustic domain and discussing the boundary normal; calculating the vibration characteristics of different loaded shipmodel in the air and water; choosing seven kinds of loaded conditions to prove; the experiences prove the results’correction.Deducing the equations of calculating the radiation characteristics of immersed structures based on FEM/FEM; calculating the example of box full of water, proving the correction of equations and programs; the results of calculating the examples of box full of air and water indicate that strong coupling effect radiation characteristics of structures heavily; finally introducing the radiation characteristics of immersed structures in infinite acoustic domain simply.It can be used as reference for solving and predicting the immersed structure vibration problems by this numerical method, and it has significance for solving the immersed structure acoustic radiation problems.