COUPLED MODE AND FINITE ELEMENT APPROXIMATIONS OF UNDERWATER SOUND PROPAGATION PROBLEMS IN GENERAL STRATIFIED ENVIRONMENTS

2008 ◽  
Vol 16 (01) ◽  
pp. 83-116 ◽  
Author(s):  
G. A. ATHANASSOULIS ◽  
K. A. BELIBASSAKIS ◽  
D. A. MITSOUDIS ◽  
N. A. KAMPANIS ◽  
V. A. DOUGALIS
Keyword(s):  
Finite Element ◽  
Sound Propagation ◽  
Test Problems ◽  
Underwater Sound ◽  
Finite Element Approximations ◽  
Coupled Mode ◽  
Cylindrically Symmetric ◽  
Mode Method ◽  
Acoustic Waveguides ◽  
Good Agreement

We compare the results of a coupled mode method with those of a finite element method and also of COUPLE on two test problems of sound propagation and scattering in cylindrically symmetric, underwater, multilayered acoustic waveguides with range-dependent interface topographies. We observe, in general, very good agreement between the results of the three codes. In some cases in which the frequency of the harmonic point source is such that an eigenvalue of the local vertical problem remains small in magnitude and changes sign several times in the vicinity of the interface nonhomogeneity, the discrepancies between the results of the three codes increase, but remain small in absolute terms.

scholarly journals ERRATUM: "COUPLED MODE AND FINITE ELEMENT APPROXIMATIONS OF UNDERWATER SOUND PROPAGATION PROBLEMS IN GENERAL STRATIFIED ENVIRONMENTS"

2009 ◽  
Vol 17 (01) ◽  
pp. 109-112
Author(s):  
G. A. ATHANASSOULIS ◽  
K. A. BELIBASSAKIS ◽  
D. A. MITSOUDIS ◽  
N. A. KAMPANIS ◽  
V. A. DOUGALIS
Keyword(s):  
Finite Element ◽  
Sound Propagation ◽  
Underwater Sound ◽  
Finite Element Approximations ◽  
Coupled Mode

scholarly journals A coupled-mode method for sound propagation with multiple sources in range-dependent waveguides

2015 ◽  
Vol 45 (1) ◽  
pp. 014301-014301
Author(s):  
WenYu LUO ◽  
RenHe ZHANG ◽  
JiXing QIN ◽  
ChunMei YANG
Keyword(s):  
Sound Propagation ◽  
Multiple Sources ◽  
Coupled Mode ◽  
Mode Method

scholarly journals A coupled-mode method for sound propagation in a range-dependent penetrable waveguide

2013 ◽  
Vol 62 (9) ◽  
pp. 094302
Author(s):  
Yang Chun-Mei ◽  
Luo Wen-Yu ◽  
Zhang Ren-He ◽  
Qin Ji-Xing
Keyword(s):  
Sound Propagation ◽  
Coupled Mode ◽  
Mode Method

A numerical comparison between the multiple-scales and finite-element solution for sound propagation in lined flow ducts

2001 ◽  
Vol 437 ◽  
pp. 367-384 ◽  
Author(s):  
SJOERD W. RIENSTRA ◽  
WALTER EVERSMAN
Keyword(s):  
Finite Element ◽  
Numerical Solutions ◽  
Sound Propagation ◽  
Multiple Scales ◽  
Finite Element Solution ◽  
Numerical Comparison ◽  
Element Solution ◽  
Mean Flow ◽  
Flow Equations ◽  
Good Agreement

An explicit, analytical, multiple-scales solution for modal sound transmission through slowly varying ducts with mean flow and acoustic lining is tested against a numerical finite-element solution solving the same potential flow equations. The test geometry taken is representative of a high-bypass turbofan aircraft engine, with typical Mach numbers of 0.5–0.7, circumferential mode numbers m of 10–40, dimensionless wavenumbers of 10–50, and both hard and acoustically treated inlet walls of impedance Z = 2 − i. Of special interest is the presence of the spinner, which incorporates a geometrical complexity which could previously only be handled by fully numerical solutions. The results for predicted power attenuation loss show in general a very good agreement. The results for iso-pressure contour plots compare quite well in the cases where scattering into many higher radial modes can occur easily (high frequency, low angular mode), and again a very good agreement in the other cases.

Reverberation Level Modeling via Coupled Mode Approach in Shallow-Water Sound Channel with Internal Solitary Waves

2018 ◽  
Vol 27 (04) ◽  
pp. 1850045 ◽  
Author(s):  
Jungyong Park ◽  
Haesang Yang ◽  
Woojae Seong ◽  
Youngmin Choo
Keyword(s):  
Shallow Water ◽  
Water Environment ◽  
Underwater Sound ◽  
Sound Channel ◽  
Trapped Mode ◽  
Coupled Mode ◽  
Shallow Water Environment ◽  
Mode Method ◽  
Abnormal Increase ◽  
Mode Energy

Reverberation level (RL) is modeled in a shallow water environment with an underwater sound channel and internal solitary wave (ISW) using the coupled mode method. Numerical RL result based on one-way coupled mode shows an abnormal increase when a source is located near the channel axis and the ISW is located far from the source. The abnormal increase is analyzed by using a two-mode approach (assuming a trapped mode and a bottom interacting mode). The two-mode approach explains the relation between the RL increase and the ISW location explicitly: the ISW transfers trapped mode energy to bottom interacting mode energy, and its increasing rate is a function of its modal attenuation and ISW location from the source. The sensitivity test according to several ISW parameters is also performed.

A Coupled-Mode Method for Acoustic Propagation and Scattering in Inhomogeneous Ocean Waveguides

2014 ◽  
Author(s):  
K. A. Belibassakis ◽  
G. A. Athanassoulis
Keyword(s):  
Bottom Topography ◽  
Three Dimensional ◽  
Acoustic Propagation ◽  
Local Mode ◽  
Scattering Problems ◽  
Coupled Mode ◽  
Cylindrically Symmetric ◽  
Present Solution ◽  
Mode Method ◽  
Additional Mode

We consider the problem of acoustic propagation and scattering in inhomogeneous waveguide governed by the Helmholtz equation. We focus on an ideal, cylindrically symmetric ocean waveguide, limited above by an acoustically soft boundary modelling the free surface, and below by a hard boundary modelling the impenetrable seabed with general bottom topography. The wave field is excited by a monochromatic point source, and thus, the present solution is equivalent to the construction of the Green’s function in the inhomogeneous domain. An improved coupled-mode method is developed, based on an enhanced local-mode series for the representation of the acoustic field, which includes an additional mode accounting for the effects of the bottom slope and curvature. The additional mode provides an implicit summation of the slowly convergent part of the series, rendering the remaining part to converge much faster, pemitting truncation of the modal expansions keeping only a few evanescent terms. Using the enhanced representation, in conjunction with an appropriate variational principle, a system of coupled-mode equations on the horizontal plane is derived for the determination of the complex modal-amplitude functions. Numerical results are presented including comparisons with analytical solutions illustrating the role and significance of the additional mode and the efficiency of the present coupled-mode tmodel, which can be naturally extended to treat propagation and scattering problems in three-dimensional, multi-layered ocean acoustic waveguides.

scholarly journals Coupled Mode Sound Propagation in Inhomogeneous Stratified Waveguides

2021 ◽  
Vol 11 (9) ◽  
pp. 3957
Author(s):  
Juan Liu ◽  
Qi Li
Keyword(s):  
Differential Equations ◽  
Sound Propagation ◽  
Computational Cost ◽  
Acoustic Medium ◽  
Acoustic Fields ◽  
Local Modes ◽  
Finite Element Software ◽  
Coupled Mode ◽  
Mode Method ◽  
Admittance Method

An efficient coupled mode method for modeling sound propagation in horizontally stratified inhomogeneous waveguides, in which the seabed is modeled as a (layered) acoustic medium, is presented. The method is based on Fawcett’s coupled mode method and the multimodal admittance method. The acoustic field is expanded onto the unusual local eigenfunctions composed by normal modes in the corresponding one-layer homogeneous waveguides with constant depth equal to the local total depth of the multilayered waveguide. A set of energy-conserving first-order differential equations governing the modal amplitudes of acoustic fields is derived. The admittance method is employed to solve the differential equations in a numerically stable manna. The coupled mode method considers the backscattering effect of inhomogeneities and full coupling between local modes, and offers improvement from the viewpoint of efficiency and computational cost. The acoustic fields predicted by the method agree well with those computed by the commercial finite element software COMSOL Multiphysics. The method can be extended to further establish fast and accurate 3D sound propagation models in complex shallow water environments.

scholarly journals Coupled mode theory of scattering by a cylindrically symmetric seamount

2016 ◽  
Vol 472 (2185) ◽  
pp. 20150465 ◽  
Author(s):  
Ronald F. Pannatoni
Keyword(s):  
Three Dimensional ◽  
Numerical Procedure ◽  
Infinite Dimensional ◽  
Coupled Mode ◽  
Cylindrically Symmetric ◽  
Finite Dimensional ◽  
Time Harmonic ◽  
Acoustic Waveguides ◽  
Algebraic Formula ◽  
Stratified Ocean

The coupled-mode equations of Shevchenko are extended to three-dimensional irregular acoustic waveguides. These equations are solved for a model of a cylindrically symmetric seamount and a time-harmonic point source in a horizontally stratified ocean. An algebraic formula for the scattered field beyond the seamount is obtained from this solution. The formula is characterized by a set of infinite-dimensional matrices that are independent of the source. A stable numerical procedure is developed to compute finite-dimensional approximations to these matrices for use in truncated versions of the formula.

scholarly journals A Finite Element Model for Underwater Sound Propagation in 2-D Environment

2021 ◽  
Vol 9 (9) ◽  
pp. 956
Author(s):  
Yi-Qing Zhou ◽  
Wen-Yu Luo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Element Model ◽  
Sound Propagation ◽  
Element Model ◽  
Two Dimensional ◽  
Underwater Sound ◽  
The Finite Element Method ◽  
The Finite Element Model ◽  
Element Method

The finite element method is a popular numerical method in engineering applications. However, there is not enough research about the finite element method in underwater sound propagation. The finite element method can achieve high accuracy and great universality. We aim to develop a three-dimensional finite element model focusing on underwater sound propagation. As the foundation of this research, we put forward a finite element model in the Cartesian coordinate system for a sound field in a two-dimensional environment. We firstly introduce the details of the implementation of the finite element model, as well as different methods to deal with boundary conditions and a comparison of these methods. Then, we use four-node quadrilateral elements to discretize the physical domain, and apply the perfectly matched layer approach to deal with the infinite region. After that, we apply the model to underwater sound propagation problems including the wedge-shaped waveguide benchmark problem and the problem where the bathymetry consists of a sloping region and a flat region. The results by the presented finite element model are in excellent agreement with analytical and benchmark numerical solutions, implying that the presented finite element model is able to solve complex two-dimensional underwater sound propagation problems accurately. In the end, we compare the finite element model with the popular normal mode model KRAKEN by calculating sound fields in Pekeris waveguides, and find that the finite element model has better universality than KRAKEN.

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