AN FFT-BASED RADIATION BOUNDARY CONDITION FOR THE PARABOLIC EQUATION

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Authors
  1. Mayfield, M.E.
Corporate Authors
Defence Research Establishment Pacific, Victoria BC (CAN);Hood Coll, Frederick MD (US) Dept of Mathematics and Computer Science
Abstract
A numerical method is presented for evaluating the Fourier transform of 1/gamma, where gamma is the specific impedance of the acoustic field. Integrals of this type arise in the formulation of a non-local, radiation boundary condition for the parabolic equation (PE). Using a procedure developed for the wavenumber-integration model SAFARI, the contour of integration is first shifted into the complex plane to avoid a singularity in the integrand. Then a fast Fourier transorm (FFT) is used to evaluate the resulting discrete approximation to the Fourier integral. This procedure is tested by comparing the numerical calculation to the known analytic Fourier transform of l/gamma for the special case of propagation over a liquid half-space.
Keywords
Parabolic equation;Specific impedance;SAFARI;Integration contour;Singular integrand;Non-local boundary condition
Report Number
DREP-CRS-94-147 — Contractor's Report Series
Date of publication
01 Dec 1994
Number of Pages
18
DSTKIM No
95-01625
CANDIS No
149444
Format(s):
Document Image stored on Optical Disk;Hardcopy

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