Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic Backscattering

Computing the backscattering of harmonic acoustic waves from underwater elastic targets of arbitrary shapes is a challenging problem of considerable practical significance. The finite element method is well suited for the discretization of the target, while the boundary element method addresses the...

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Main Authors: Petr Krysl, Ahmad T. Abawi
Format: Article
Language:English
Published: MDPI AG 2023-05-01
Series:Acoustics
Subjects:
Online Access:https://www.mdpi.com/2624-599X/5/2/31
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author Petr Krysl
Ahmad T. Abawi
author_facet Petr Krysl
Ahmad T. Abawi
author_sort Petr Krysl
collection DOAJ
description Computing the backscattering of harmonic acoustic waves from underwater elastic targets of arbitrary shapes is a challenging problem of considerable practical significance. The finite element method is well suited for the discretization of the target, while the boundary element method addresses the radiation boundary condition at infinity. A disadvantage of the boundary integral method is that it yields non-unique solutions at certain wavenumbers. This failure is associated with the existence of eigensolutions of the Helmholtz equation in the interior of the complement of the fluid domain (acoustic modes). The combined Helmholtz integral equation formulation (CHIEF) credited to Schenk is employed to combine the surface Helmholtz boundary integral with equations of the interior Helmholtz relation written down at selected points within the cavity of the scatterer (i.e., in the complement of the fluid domain).The difficulty associated with this approach has always been the lack of guidance on the necessary number of interior points and on their locations. The solution to this problem proposed here is to compute the acoustic modes using the finite element method to complement of the fluid domain and to identify locations of the peaks.This novel approach aids the decision as to how many points should be employed and where they should be located. Our numerical experiments demonstrate the robustness of the proposed automatic selection of the CHIEF points’ numbers and locations.
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spelling doaj.art-e5046791b7a249d5bf8739746c8bf7cf2023-11-18T08:48:22ZengMDPI AGAcoustics2624-599X2023-05-015252253410.3390/acoustics5020031Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic BackscatteringPetr Krysl0Ahmad T. Abawi1Structural Engineering Department, University of California, San Diego, CA 92093, USAHeat, Light, and Sound Research, Inc., 1130 Wall Street #518, La Jolla, CA 92037, USAComputing the backscattering of harmonic acoustic waves from underwater elastic targets of arbitrary shapes is a challenging problem of considerable practical significance. The finite element method is well suited for the discretization of the target, while the boundary element method addresses the radiation boundary condition at infinity. A disadvantage of the boundary integral method is that it yields non-unique solutions at certain wavenumbers. This failure is associated with the existence of eigensolutions of the Helmholtz equation in the interior of the complement of the fluid domain (acoustic modes). The combined Helmholtz integral equation formulation (CHIEF) credited to Schenk is employed to combine the surface Helmholtz boundary integral with equations of the interior Helmholtz relation written down at selected points within the cavity of the scatterer (i.e., in the complement of the fluid domain).The difficulty associated with this approach has always been the lack of guidance on the necessary number of interior points and on their locations. The solution to this problem proposed here is to compute the acoustic modes using the finite element method to complement of the fluid domain and to identify locations of the peaks.This novel approach aids the decision as to how many points should be employed and where they should be located. Our numerical experiments demonstrate the robustness of the proposed automatic selection of the CHIEF points’ numbers and locations.https://www.mdpi.com/2624-599X/5/2/31coupled finite element and boundary elementacoustic backscatteringCHIEF
spellingShingle Petr Krysl
Ahmad T. Abawi
Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic Backscattering
Acoustics
coupled finite element and boundary element
acoustic backscattering
CHIEF
title Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic Backscattering
title_full Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic Backscattering
title_fullStr Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic Backscattering
title_full_unstemmed Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic Backscattering
title_short Automatic CHIEF Point Selection for Finite Element–Boundary Element Acoustic Backscattering
title_sort automatic chief point selection for finite element boundary element acoustic backscattering
topic coupled finite element and boundary element
acoustic backscattering
CHIEF
url https://www.mdpi.com/2624-599X/5/2/31
work_keys_str_mv AT petrkrysl automaticchiefpointselectionforfiniteelementboundaryelementacousticbackscattering
AT ahmadtabawi automaticchiefpointselectionforfiniteelementboundaryelementacousticbackscattering