Publication Date:
2022-05-25
Description:
Author Posting. © Acoustical Society of America, 1996. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 100 (1996): 2070-2078, doi:10.1121/1.417917.
Description:
A numerical scattering chamber based on the time-domain finite-difference solution of the two-way elastic wave equation is applied to a sea surface scattering problem, and excellent agreement is obtained in amplitude and phase with a reference solution obtained by an integral equation method. The sea surface roughness is one representation of a Pierson–Moskowitz spectrum for a wind speed of 15 m/s. The incident field is a 400-Hz continuous wave generated by a Gaussian tapered vertical array. This problem demonstrates a number of issues in numerical modeling of wave scattering. The spreading of Gaussian beams, even in homogeneous media, creates an asymmetry in the insonification of the surface footprint or scattering area. Because of beamspreading, Gaussian tapered vertical arrays do not generate Gaussian beams. Scattering from a rough, free, fluid surface can be accurately solved with careful treatment of the numerical boundary representing the free surface. Continuous wave (cw) scattering problems can be solved in the time domain. For the second-order, explicit, staggered finite-difference formulation used in this study, a spatial sampling of 20 points per acoustic wavelength was necessary for acceptable grid dispersion. However, to correctly compute the scattered field for the test model, it was sufficient to specify the free surface at a spatial sampling of only ten points per acoustic wavelength.
Description:
This
work was carried out under Office of Naval Research Grant
Nos. N00014-90-J-1493, N00014-95-1-0506, and N00014-
96-1-0460.
Keywords:
Underwater
;
Sea bed
;
Sea surfaces
;
Sound waves
;
Backscattering
;
Mathematical models
;
Time domain analysis
;
Finite difference method
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
Permalink