Application of the fast multipole boundary element method to underwater acoustic scattering

Abstract

A numerical model is being developed in the MATLAB programming environment to model the acoustic field scattered from a submarine hull. Due to the acoustic impedance properties of water, small particle velocities yield large acoustic pressures, resulting in coupled fluid-structure interactions. Numerical methods can be employed to calculate the scattered acoustic field for complex geometries. Traditionally, these techniques required both significant memory and computational time, limiting their usefulness. Recently, the fast multipole algorithm (FMA) has been used to efficiently calculate the acoustic field on an object’s surface, while the finite element method was used to model the object’s interior. The pressure hull of a submarine can be represented as a piecewise continuous isotropic elastic solid, thus the FMA can also model the submarine interior, with the unknowns expressed on each surface. A possible method for coupling an exterior acoustic model to a structural model, both calculated via the FMA, is outlined here. Some initial acoustic fast multipole boundary element method results are presented.

Keywords:

• Coupled fluid-structure interactions
• fast multipole method
• underwater acoustics

Additional information

Notes on contributors

D R Wilkes

Daniel R. Wilkes is currently completing his PhD at Curtin University, under the tutelage of Alec J. Duncan (PhD supervisor). Daniel previously studied at Curtin University for his degrees in applied physics. His research interests include coupled fluid-structure interactions and numerical modelling.

A J Duncan

Alec J. Duncan is a Senior Research Fellow at Curtin University’s Centre for Marine Science and Technology, and a Senior Lecturer in the university’s Department of Imaging and Applied Physics. He has an undergraduate degree in applied physics from the Royal Melbourne Institute of Technology, and both a Masters degree and PhD from Curtin University. His research interests are in underwater acoustics, a field he has been working in since the beginning of a four-year stint at the University of Bath, UK, in the 1980s. His main areas of expertise are in the development of underwater acoustic instrumentation, sonar and array signal processing, and modelling the propagation of underwater sound.