A FINITE-DIFFERENCE TIME-DOMAIN SOLUTION TO SCATTERING FROM A ROUGH PRESSURE-RELEASE SURFACE

The finite-difference time-domain (FDTD) method is a numerical techniq ue that makes no explicit physical approximations to the underlying pr oblem, The quality of a FDTD-based solution typically is determined by the discretization of the computational domain-the smaller the spacin g, the more accurate the solution. Unfortunately, for large computatio nal domains, i.e., ones spanning many wavelengths, the small spatial s tep size needed to obtain a high-fidelity solution may lead to a prohi bitively large number of unknowns, Herl it is shown how the FDTD metho d can be used to model accurately scattering from pressure-release sur faces above a homogeneous water column. To keep the computational cost manageable, a number of enhancements to the standard FDTD algorithm a re employed, These enhancements include correcting for numerical dispe rsion along the specular direction of the incident insonification, usi ng locally conformal cells at the pressure-release boundary, and propa gating the field through the homogeneous water column via an analytic method. The accuracy of the FDTD approach is demonstrated by compariso n with an integral equation-based reference solution to the same rough surface scattering problem [Thorsos, Proceedings of the Reverberation and Scattering Workshop, pp. 3.2-3.20 (1994) Naval Research Laborator y Book Contribution NRL/BE/7181-96-001]. (C) 1997 Acoustical Society o f American. [S0001-4966(97)03912-X].