Multiple Multipole Expansions For Elastic Scattering: An Aid To Understanding The Problems In "No-Record" Areas
Name
1996.13 Imhof.pdf
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877.76 KB
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Checksum (MD5)
8b0930ef32315d311984dad27b2e9dab
Author(s)
Imhof, Matthias G.
Date Issued
1996
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1996-13
Abstract
This paper presents a new approach to solving scattering of elastic waves in two dimensions. Wavefields are often expanded into an orthogonal set of basis functions.
Unfortunately, these expansions converge rather slowly for complex geometries. The
new approach enhances convergence by summing multiple expansions with different
centers of expansion. This allows irregularities of the boundary to be resolved locally
from a nearby center of expansion. Mathematically, the wavefields are expanded into
a set of non-orthogonal basis functions. The incident wavefield and the fields induced
by the scatterers are matched by evaluating the boundary conditions at discrete matching
points along the domain boundaries. Due to the non-orthogonal expansions, more
matching points are used than actually needed, resulting in an overdetermined system
which is solved in the least squares sense.
Since there are free parameters such as the location and number of expansion centers
as well as the kind and orders of expansion functions used, numerical experiments
are performed to measure the performance of different discretizations. An empirical
set of rules governing the choice of these parameters is found from these experiments.
The resulting algorithm is a general tool to solve relatively large and complex two-dimensional scattering problems.
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