Scattering from rough fluid–fluid interfaces using the finite-difference time-domain method

Abstract

The finite-difference time-domain (FDTD) method is a numerical technique that can be used to solve a wide variety of problems via time-domain simulations. Results have been presented for scattering from pressure-release surfaces [F. Hastings et al., IEEE Trans. Antennas Propagat. 43, 1183–1191 (1995)] based on the FDTD method. This paper describes the use of the FDTD technique to study scattering from rough fluid–fluid interfaces. Precise results are obtained by employing several enhancements to the FDTD algorithm. Most importantly, a grid conforming to the rough interface is used to achieve accurate results at a reasonable computational cost. This is in contrast to a traditional stair-stepped model of the interface which gives spurious overprediction of the backscattered field. Numerical results are presented for the scattering strength obtained using a Monte Carlo technique and are compared with results obtained using a Monte Carlo integral equation approach. For both methods, the incident field is a tapered plane wave, and 50 surface realizations are used to obtain the average scattering strength. One advantage of the FDTD method is that it allows the addition of heterogeneities at little extra computational cost. [Work supported by ONR.]