Acoustic Radiation and Scattering Response from Hybrid Structures

• Main Authors: Lai,Sheng-Yang, 賴聲揚
• Other Authors: Chen, Yung-Wei
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/7vkvb9

碩士 === 國立臺灣海洋大學 === 輪機工程學系 === 106 === In this thesis, we study the acoustic radiation and scattering response from Hybrid Structures. It is very important issue for controlling radiation and scattering of underwater acoustic fields. However, how to predict them effectively and to reduce the response is a really important research. The acoustic radiation is caused by the excitation of external force from the structure itself and coupled with the underwater fluid. To solve the fluid –structure interaction (FSI), it need to solve the structural equation and acoustic wave equation by the finite element method (FEM) and boundary element method (BEM). The scattering phenomenon is forced to deviate from a straight trajectory by one or more paths due to the incidence of external plane wave on obstacle. For the scattering phenomenon, the BEM is applied to describe. Therefore, in this thesis we used FEM/BEM to solve the acoustic radiation and BEM for the acoustic scattering. In order to prevent the occurrence of acoustic radiation and scattering, we used different types of materials to cover the geometry and then prevent the generation of underwater radiation and scattering. Radiation reduces the noise by applying a damping material to change the structure of the geometry; while scattering is change the impedance of the composite material to reduce the sound pressure generated by itself. We verified the material parameters by experiments and compare to the results with analyses of finite element method. In the meanwhile, we compared numerical solutions with analytical solutions. The results showed that the current methods in this thesis can compute the radiation and scattering of the underwater geometry efficiently and precisely.