Abstract:

The finite-difference time-domain (FDTD) formulation [S. Wang, J. Acoust. Soc. Am. 99, 1924--1931 (1996)] and the least-squares absorbing boundary conditions [S. Wang, Chin. J. Acoust. 16, 121--134 (1997)] have been successfully applied to deal with sound scattering from ideally soft and ideally rigid objects with arbitrary shapes. To expand the scope of application to more realistic cases, an effective boundary treatment for interfaces penetrable to sound waves is introduced. The FDTD boundary condition expressions take a form similar to that in continuous and uniform media, except for a modification to the material-related constants. This is achieved by using a suitable averaging scheme based on a second-order discretization of the basic acoustic equations on boundaries. The proposed method is consistent with the ideal cases at both soft and rigid ends, giving a unified approach to the solution of scattering from nonelastic objects. Numerical experiments on scattering from various objects submerged in water are presented, showing a good agreement with theoretical solutions and previously obtained results. The object materials used in the computation cover a wide range of acoustic impedance from very soft to very rigid. [Work supported by NNSFC.]