A New Tool for Ship-Marine Machinery Noise Analysis 2009-01-2195

There are three criteria for an ideal ship-marine machinery noise analysis tool: It is applicable over a wide frequency range, it has modeling fidelity, and it is economical and can be used for design iterations. Vibratory energy from the machinery sources to the ocean follows 3-dimensional paths. Energy is attenuated by isolations, structural discontinuities, damping treatment, before radiated to the water. Traditionally, Finite Element Method (FEM), Boundary Element Analysis (BEM), and Statistical Energy Analysis (SEA) are used for noise analysis. FEM models can be constructed to follow complex machine geometry well. However, its applicable frequency range is limited by the practical mesh size. On the other hand, SEA can be used in the middle to high frequency ranges where the system modal density is adequate. The basic building blocks of a SEA model consist of plates, shells, and beams. For complex machinery components, the fidelity of SEA is sacrificed by the limitation of available choices of building blocks.

A new approach, Generalized Dynamic Analysis Procedure (GENDAP), an implementation of DEA (Dynamic Element Analysis), is proposed in this paper for ship-machinery noise analysis. GENDAP uses FEA meshes to model a structure; hence it has good modeling fidelity. In the low frequency range, its prediction converges to those calculated by FEA; in the high frequency range it has the same mean value as provided by the SEA. A set of carefully selected benchmark problems were used to validation this approach for ship-machinery noise analysis applications.