Noise from structural vibration is a major consideration in the design and manufacturing of a product, such as an automobile, airplane, and other consumer goods. Acoustic simulation is an important step to optimize the performance of many new products early in the design stage rather than correcting the mistakes afterwards. Effective and efficient numerical modeling and simulation methods will be important tools for noise prediction during the design stage of products.
This thesis work focuses on integrating the numerical methods in the prediction of noise from vibrating structures. To calculate the sound radiated from a vibrating structure, both a structural dynamic problem and an acoustic wave problem should be considered. In this study, the finite element method (FEM) is chosen for the structural dynamic analysis in order to calculate the natural frequencies and harmonic responses of the structure. The boundary element method (BEM) is used in the acoustic analysis of the structure to calculate the radiated sound field. In the BEM, only the surface of a sound radiating structure is discretized and the simulation of sound fields in unbounded domains is easy, yielding an efficient mesh generation and preprocessing. To couple the FEM analysis with the BEM analysis, a computer program, or translation code, is developed for mapping the model and velocity boundary condition (BC) for the acoustic analysis from the results of the dynamic analysis. Several element types in the FEM using the software ABAQUS® are implemented in the translation code and their performances are studied. Different BEM solvers in the software FastBEM Acoustics® developed earlier at the University of Cincinnati (UC) and based on the fast multipole method (FMM), the adaptive cross approximation (ACA) method and the fast conventional BEM are selected in this study. The correctness and feasibility of the developed code are verified using a pulsating sphere model and a vibrating plate model. Numerical results and analytical data are found to be in good agreement using the developed translation code. As a large-scale and practical application, a wind turbine model is also used to study the noise propagation on the ground due to the vibration of the turbine structure and the rotation of turbine blades. It is found that the coupled analysis with the FEM and BEM can model the noise prediction of large-scale structures effectively and efficiently.