An FDTD method for analysis of scattering from rough fluid-fluidinterfaces |
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| Authors: | Hastings FD Schneider JB Broschat SL Thorsos EI |
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| Institution: | Sch. of Electr. Eng. & Comput. Sci., Washington State Univ., Pullman, WA; |
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| Abstract: | A finite-difference time-domain (FDTD) method for scattering by one-dimensional, rough fluid-fluid interfaces is presented, modifications to the traditional FDTD algorithm are implemented which yield greater accuracy at lower computational cost. These modifications include use of a conformal technique, in which the grid conforms locally to the interface, and a correction for the numerical dispersion inherent to the FDTD algorithm, Numerical results are presented for fluid-fluid cases modeling water-sediment interfaces. Two different roughness spectra, the single-scale Gaussian roughness spectrum and a multiscale modified power-law spectrum, are used. The Gaussian results are calculated as a function of the dimensionless parameters kh and kl, where k is the wavenumber in water, h is the rms surface height, and l is the surface correlation length. For the modified power-law spectrum, statistical parameters consistent with an insonification frequency of 7.5 kHz are used. Results are compared with those obtained using an integral equation technique both for scattering from single-surface realizations and for Monte Carlo averages of scattering from an ensemble of surface realizations. Scattering strengths are calculated as a function of scattering angle for an incident angle of 70° (20° grazing). The results agree well over all scattering angles for the cases examined |
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