Time‐domain numerical simulation of scattering by objects in the seafloor.

Abstract

Numerical simulation of scattering in the time domain offers potential implementation advantages in comparison with frequency‐domain methods. By using explicit numerical time integration schemes, elastic stresses and velocities can typically be advanced using only spatially local information which makes parallelization by domain decomposition straightforward to implement in comparison with the solution of a large linear system of equations. On the other hand, incorporation of frequency‐dependent sound speed and attenuation appears more challenging in the time domain with the general need to compute convolutions under non‐FFT friendly conditions. This talk presents efficiency gains for the elastodynamic finite integration technique (EFIT) which is similar to the finite‐difference time‐domain method (FDTD). We present results on using explicit decomposition of scattered and incident wave fields and far‐field projection in the time domain with the discrete Helmholtz–Kirchhoff integral. We also present incorporation of frequency‐dependent material parameters by efficient recursive convolution techniques that have been used successfully to create time‐domain perfectly matched layers [J. A. Roden and S. D. Gedney, Microwave Opt. Technol. Lett. 27, 334–338, (2000)]. As an application example, we present results on computing bistatic target strength variance for a two‐dimensional object located near a statistically rough seafloor. [Work sponsored by the Office of Naval Research.]