Advanced simulations of Underwater Radiated Noise (URN) predictions for naval ships

Characteristics of underwater Radiated Noise (URN) is an important index to evaluate stealth performance of naval vessels. In general, URN signature is measured after the vessel is built and at that stage any effort to minimize URN becomes a big challenge as consequential structural modification or changes to any critical machinery may lead to substantial cost implications and in some scenarios might not be possible. Hence, it is always beneficial to perform design iterations based on URN predictions at the initial design stage. In recent years numerical simulations have evolved a lot especially in the field of aerospace and automobile industry. The perfectly matched layer (PML), recently formulated by Berenger, for the absorption of radiated/scattered waves in computational acoustics and its effectiveness as a non-reflecting boundary, is applied to predict the sound radiated/scattered in far field. This paper explains a hybrid approach involving finite element method (FEM) and adaptive PML model for structure borne noise (SBN) due to critical mechanical machinery and Computational Fluid Dynamics (CFD) - Boundary Element Method (BEM) model for hydrodynamic noise due to propeller action. This paper addresses some of the challenges encountered and demonstrates how they can be mitigated using hybrid approach and the use of novel techniques.