Pub Date : 2016-08-30DOI: 10.1142/S0218396X16500107
Peng Xiao, Kunde Yang
Temporal coherence of a propagating signal in the fluctuating ocean is an important property for many practical applications. In previous studies, it has been shown that the coherence time follows a − 3/2 power frequency dependence and a − 1/2 power range dependence for long-range deep-water propagations as well as for shallow water propagations. In this paper, the frequency and range dependences are studied for a relative near distance in the deep ocean based on the Monte Carlo simulations. The range is tens of kilometers and it cannot be regard as a long-range propagation. It is found in this paper that the − 3/2 power frequency dependence is still followed, while the simple − 1/2 power relationship is inadequate to show the range dependence in the near field of deep water. The signals mainly propagate through two different paths for tens of kilometers: the refracted path and the reflected paths. In different regions, the acoustic coherence times exhibit different dependences because the signals are dom...
{"title":"Temporal Coherence of Acoustic Signal Transmissions in a Fluctuating Deep Ocean","authors":"Peng Xiao, Kunde Yang","doi":"10.1142/S0218396X16500107","DOIUrl":"https://doi.org/10.1142/S0218396X16500107","url":null,"abstract":"Temporal coherence of a propagating signal in the fluctuating ocean is an important property for many practical applications. In previous studies, it has been shown that the coherence time follows a − 3/2 power frequency dependence and a − 1/2 power range dependence for long-range deep-water propagations as well as for shallow water propagations. In this paper, the frequency and range dependences are studied for a relative near distance in the deep ocean based on the Monte Carlo simulations. The range is tens of kilometers and it cannot be regard as a long-range propagation. It is found in this paper that the − 3/2 power frequency dependence is still followed, while the simple − 1/2 power relationship is inadequate to show the range dependence in the near field of deep water. The signals mainly propagate through two different paths for tens of kilometers: the refracted path and the reflected paths. In different regions, the acoustic coherence times exhibit different dependences because the signals are dom...","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"33 1","pages":"1650010"},"PeriodicalIF":0.0,"publicationDate":"2016-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500107","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64077098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-08-30DOI: 10.1142/S0218396X16500120
E. Perrey-Debain, R. Maréchal, J. Ville
In this work, acoustic performances of a liner concept based on perforated screens backed by air cavities are investigated numerically for circular ducts with mean flow. Dimensions of the cavity are chosen to be of the order or bigger than the wavelength so acoustic waves within the liner can propagate parallel to the duct surface. In this case, the liner becomes nonlocally reacting and this gives rise to additional resonance effects which renders the attenuation more effective over a broader frequency range. In order to predict the mufflers’ acoustic performances, a special boundary integral method is presented. Using a tailored Green’s function for hard wall circular ducts containing uniform mean flow, the numerical technique only requires the discretization of the acoustic velocity potential on both sides of the perforated screen separating the central channel from the air cavities. Comparisons with finite element results show that the proposed method allows accurate results for a relatively modest computational cost. Influence of the mean flow in the central airway, the dimensions of the cavity as well as the nature of the incident field on acoustic performances are also shown and discussed.
{"title":"A Special Boundary Integral Method for the Numerical Simulation of Sound Propagation in Flow Ducts Lined with Multi-Cavity Resonators","authors":"E. Perrey-Debain, R. Maréchal, J. Ville","doi":"10.1142/S0218396X16500120","DOIUrl":"https://doi.org/10.1142/S0218396X16500120","url":null,"abstract":"In this work, acoustic performances of a liner concept based on perforated screens backed by air cavities are investigated numerically for circular ducts with mean flow. Dimensions of the cavity are chosen to be of the order or bigger than the wavelength so acoustic waves within the liner can propagate parallel to the duct surface. In this case, the liner becomes nonlocally reacting and this gives rise to additional resonance effects which renders the attenuation more effective over a broader frequency range. In order to predict the mufflers’ acoustic performances, a special boundary integral method is presented. Using a tailored Green’s function for hard wall circular ducts containing uniform mean flow, the numerical technique only requires the discretization of the acoustic velocity potential on both sides of the perforated screen separating the central channel from the air cavities. Comparisons with finite element results show that the proposed method allows accurate results for a relatively modest computational cost. Influence of the mean flow in the central airway, the dimensions of the cavity as well as the nature of the incident field on acoustic performances are also shown and discussed.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1650012"},"PeriodicalIF":0.0,"publicationDate":"2016-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500120","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64077474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-08-30DOI: 10.1142/S0218396X16500089
Jinghe Li, Q. Liu
The fast scattering and inverse scattering algorithms for acoustic wave propagation and scattering in a layered medium with buried objects are an important research topic, especially for large-scale geophysical applications and for target detection. There have been increasing efforts in the development of practical, accurate, and efficient means of imaging subsurface target anomalies. In this work, the acoustic scattering problem in layered media is formulated as a volume integral equation and is solved by the stabilized bi-conjugate gradient fast Fourier transform (BCGS-FFT) method. By splitting the layered medium Green’s function interacting with the induced source into a convolution and a correlation, the acoustic fields can be calculated efficiently by the FFT algorithm. This allows both the forward solution and inverse solution to be computed with only O(Nlog N) computation time per iteration, where N is the number of degrees of freedom. The inverse scattering is solved using a simultaneous multiple ...
{"title":"Fast Frequency-Domain Forward and Inverse Methods for Acoustic Scattering from Inhomogeneous Objects in Layered Media","authors":"Jinghe Li, Q. Liu","doi":"10.1142/S0218396X16500089","DOIUrl":"https://doi.org/10.1142/S0218396X16500089","url":null,"abstract":"The fast scattering and inverse scattering algorithms for acoustic wave propagation and scattering in a layered medium with buried objects are an important research topic, especially for large-scale geophysical applications and for target detection. There have been increasing efforts in the development of practical, accurate, and efficient means of imaging subsurface target anomalies. In this work, the acoustic scattering problem in layered media is formulated as a volume integral equation and is solved by the stabilized bi-conjugate gradient fast Fourier transform (BCGS-FFT) method. By splitting the layered medium Green’s function interacting with the induced source into a convolution and a correlation, the acoustic fields can be calculated efficiently by the FFT algorithm. This allows both the forward solution and inverse solution to be computed with only O(Nlog N) computation time per iteration, where N is the number of degrees of freedom. The inverse scattering is solved using a simultaneous multiple ...","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1650008"},"PeriodicalIF":0.0,"publicationDate":"2016-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500089","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64077444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-08-30DOI: 10.1142/S0218396X16500193
Katherine F. Woolfe, M. D. Collins, D. Calvo, W. Siegmann
The accuracy of the seismo-acoustic parabolic equation is tested for problems involving sloping solid–solid interfaces and variable topography. The approach involves approximating the medium in terms of a series of range-independent regions, using a parabolic wave equation to propagate the field through each region, and applying a single-scattering approximation to obtain transmitted fields across the vertical interfaces between regions. The accuracy of the parabolic equation method for range-dependent problems in seismo-acoustics was previously tested in the small slope limit. It is tested here for problems involving larger slopes using a finite-element model to generate reference solutions.
{"title":"Seismo-Acoustic Benchmark Problems Involving Sloping Solid–Solid Interfaces and Variable Topography","authors":"Katherine F. Woolfe, M. D. Collins, D. Calvo, W. Siegmann","doi":"10.1142/S0218396X16500193","DOIUrl":"https://doi.org/10.1142/S0218396X16500193","url":null,"abstract":"The accuracy of the seismo-acoustic parabolic equation is tested for problems involving sloping solid–solid interfaces and variable topography. The approach involves approximating the medium in terms of a series of range-independent regions, using a parabolic wave equation to propagate the field through each region, and applying a single-scattering approximation to obtain transmitted fields across the vertical interfaces between regions. The accuracy of the parabolic equation method for range-dependent problems in seismo-acoustics was previously tested in the small slope limit. It is tested here for problems involving larger slopes using a finite-element model to generate reference solutions.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1650019"},"PeriodicalIF":0.0,"publicationDate":"2016-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500193","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64078460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-08-18DOI: 10.1142/S0218396X16500053
Jiangang Xie, Zichao Guo, Hai Liu, Q. Liu
We propose a pre-stack reverse time migration (RTM) seismic imaging method using the pseudospectral time-domain (PSTD) algorithm. Traditional pseudospectral method uses the fast Fourier transform (FFT) algorithm to calculate the spatial derivatives, but is limited by the wraparound effect due to the periodicity assumed in the FFT. The PSTD algorithm combines the pseudospectral method with a perfectly matched layer (PML) for acoustic waves. PML is a highly effective absorbing boundary condition that can eliminate the wraparound effect. It enables a wide application of the pseudospectral method to complex models. RTM based on the PSTD algorithm has advantages in the computational efficiency compared to traditional methods such as the second-order and high order finite difference time-domain (FDTD) methods. In this work, we implement the PSTD algorithm for acoustic wave equation based RTM. By applying the PSTD-RTM method to various seismic models and comparing it with RTM based on the eighth-order FDTD method, we find that PSTD-RTM method has better performance and saves more than 50% memory. The method is suitable for parallel computation, and has been accelerated by general purpose graphics processing unit.
{"title":"Reverse Time Migration Using the Pseudospectral Time-Domain Algorithm","authors":"Jiangang Xie, Zichao Guo, Hai Liu, Q. Liu","doi":"10.1142/S0218396X16500053","DOIUrl":"https://doi.org/10.1142/S0218396X16500053","url":null,"abstract":"We propose a pre-stack reverse time migration (RTM) seismic imaging method using the pseudospectral time-domain (PSTD) algorithm. Traditional pseudospectral method uses the fast Fourier transform (FFT) algorithm to calculate the spatial derivatives, but is limited by the wraparound effect due to the periodicity assumed in the FFT. The PSTD algorithm combines the pseudospectral method with a perfectly matched layer (PML) for acoustic waves. PML is a highly effective absorbing boundary condition that can eliminate the wraparound effect. It enables a wide application of the pseudospectral method to complex models. RTM based on the PSTD algorithm has advantages in the computational efficiency compared to traditional methods such as the second-order and high order finite difference time-domain (FDTD) methods. In this work, we implement the PSTD algorithm for acoustic wave equation based RTM. By applying the PSTD-RTM method to various seismic models and comparing it with RTM based on the eighth-order FDTD method, we find that PSTD-RTM method has better performance and saves more than 50% memory. The method is suitable for parallel computation, and has been accelerated by general purpose graphics processing unit.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1650005"},"PeriodicalIF":0.0,"publicationDate":"2016-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500053","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64077131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-08-18DOI: 10.1142/S0218396X15500204
Q. Serra, M. Ichchou, J. Deü
The transfer matrix method (TMM) is a famous analytic method in the vibroacoustic community. It is classically considered as a high frequency approach, because of the hypothesis of acoustic plane waves impinging on a flat infinite panel. Thus, it cannot take into account directly finite-size effects or lateral boundary conditions (BCs), and it needs specific algorithms to correct its results in the low frequency range. Within the transfer matrix framework, the use of finite elements makes it possible to generalize the range of applications of transfer approaches. Thus, the study of wave propagation in poroelastic media, in presence of lateral BCs can be carried out. The links between theses waves and the acoustic response of a sample are investigated. Finally, it shows that transfer approaches are not limited in the low frequency range, as usually stated. In fact, the validity of analytic transfer approaches depends more on the material and on the geometry than on the frequency range.
{"title":"On the Use of Transfer Approaches to Predict the Vibroacoustic Response of Poroelastic Media","authors":"Q. Serra, M. Ichchou, J. Deü","doi":"10.1142/S0218396X15500204","DOIUrl":"https://doi.org/10.1142/S0218396X15500204","url":null,"abstract":"The transfer matrix method (TMM) is a famous analytic method in the vibroacoustic community. It is classically considered as a high frequency approach, because of the hypothesis of acoustic plane waves impinging on a flat infinite panel. Thus, it cannot take into account directly finite-size effects or lateral boundary conditions (BCs), and it needs specific algorithms to correct its results in the low frequency range. Within the transfer matrix framework, the use of finite elements makes it possible to generalize the range of applications of transfer approaches. Thus, the study of wave propagation in poroelastic media, in presence of lateral BCs can be carried out. The links between theses waves and the acoustic response of a sample are investigated. Finally, it shows that transfer approaches are not limited in the low frequency range, as usually stated. In fact, the validity of analytic transfer approaches depends more on the material and on the geometry than on the frequency range.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1550020"},"PeriodicalIF":0.0,"publicationDate":"2016-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X15500204","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64076932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-08-18DOI: 10.1142/S0218396X16500065
R. Troian, K. Shimoyama, F. Gillot, S. Besset
Reducing the noise level in the acoustic cavities is the important problem when treating inflight conditions of commercial planes or boats. Shape optimization of the acoustic cavity that will take into account the geometrical and material uncertainties, arising during the manufacturing process, is presented in this paper. The noise level is controlled by minimizing the energy density in the cavity, obtained through an energy method called Simplified Energy Method. Such formulation is based on our previous published work where transformation function mapping 3D cavity surface on a 2D domain was proposed. The optimization process directly relies on this function and thus avoids remeshing of the geometry. Robust optimization is performed using the nondominated sorting genetic algorithm (NSGA-II) together with the Kriging surrogate model. Influence of geometrical and material characteristics on the optimal solution is identified.
{"title":"Methodology for the Design of the Geometry of a Cavity and Its Absorption Coefficients as Random Design Variables Under Vibroacoustic Criteria","authors":"R. Troian, K. Shimoyama, F. Gillot, S. Besset","doi":"10.1142/S0218396X16500065","DOIUrl":"https://doi.org/10.1142/S0218396X16500065","url":null,"abstract":"Reducing the noise level in the acoustic cavities is the important problem when treating inflight conditions of commercial planes or boats. Shape optimization of the acoustic cavity that will take into account the geometrical and material uncertainties, arising during the manufacturing process, is presented in this paper. The noise level is controlled by minimizing the energy density in the cavity, obtained through an energy method called Simplified Energy Method. Such formulation is based on our previous published work where transformation function mapping 3D cavity surface on a 2D domain was proposed. The optimization process directly relies on this function and thus avoids remeshing of the geometry. Robust optimization is performed using the nondominated sorting genetic algorithm (NSGA-II) together with the Kriging surrogate model. Influence of geometrical and material characteristics on the optimal solution is identified.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1650006"},"PeriodicalIF":0.0,"publicationDate":"2016-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500065","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64077223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-08-18DOI: 10.1142/S0218396X16500041
A. Mimani, M. Munjal
This work presents a semi-analytical technique based on the Green's function and uniform-piston driven model to determine the end-correction length l in an axially long flow-reversal end chamber muffler having an end-inlet and an end-outlet. The semi-analytical procedure is based on the 3D analytical uniform piston-driven model for obtaining the impedance Z] matrix parameters and numerically evaluating the frequency f(p) at which the imaginary part of the cross-impedance parameter Z(E2E1) crosses the frequency axis at the first instance. The frequency f(p) corresponds to the low-frequency peak in the transmission loss (TL) spectrum of the axially long flow-reversal end-chamber muffler obtained a priori to its computation by considering the influence of higher order evanescent transverse modes. The effective chamber length (and thence, the end-correction length) in the low-frequency range are determined by using the expression for resonance frequency of a classical quarter-wave resonator. This method is employed to determine the end-correction in axially long elliptical cylindrical end chambers and circular cylindrical end chambers (with or without a rigid concentric circular pass-tube). The TL graph predicted by the 1D axial plane wave model (incorporating the end-correction length) is shown to be in an excellent agreement with that obtained by the 3D analytical approach and an experimental result (from literature) up to the low-frequency limit, thereby validating the semi-analytical technique. Parametric studies are conducted using the proposed semi-analytical method to investigate and qualitatively explain the effect of angular location and offset distance of the end ports and the pass-tube diameter on the end-correction length, thereby yielding important insights into the influence of transverse evanescent modes on dominant axial plane wave modes of the axially long end-chamber. Development of an empirical end-correction expression in a flow-reversal circular end-chamber with offset inlet and outlet ports is a practically useful contribution of this work.
{"title":"Acoustic End-Correction in a Flow-Reversal End Chamber Muffler: A Semi-Analytical Approach","authors":"A. Mimani, M. Munjal","doi":"10.1142/S0218396X16500041","DOIUrl":"https://doi.org/10.1142/S0218396X16500041","url":null,"abstract":"This work presents a semi-analytical technique based on the Green's function and uniform-piston driven model to determine the end-correction length l in an axially long flow-reversal end chamber muffler having an end-inlet and an end-outlet. The semi-analytical procedure is based on the 3D analytical uniform piston-driven model for obtaining the impedance Z] matrix parameters and numerically evaluating the frequency f(p) at which the imaginary part of the cross-impedance parameter Z(E2E1) crosses the frequency axis at the first instance. The frequency f(p) corresponds to the low-frequency peak in the transmission loss (TL) spectrum of the axially long flow-reversal end-chamber muffler obtained a priori to its computation by considering the influence of higher order evanescent transverse modes. The effective chamber length (and thence, the end-correction length) in the low-frequency range are determined by using the expression for resonance frequency of a classical quarter-wave resonator. This method is employed to determine the end-correction in axially long elliptical cylindrical end chambers and circular cylindrical end chambers (with or without a rigid concentric circular pass-tube). The TL graph predicted by the 1D axial plane wave model (incorporating the end-correction length) is shown to be in an excellent agreement with that obtained by the 3D analytical approach and an experimental result (from literature) up to the low-frequency limit, thereby validating the semi-analytical technique. Parametric studies are conducted using the proposed semi-analytical method to investigate and qualitatively explain the effect of angular location and offset distance of the end ports and the pass-tube diameter on the end-correction length, thereby yielding important insights into the influence of transverse evanescent modes on dominant axial plane wave modes of the axially long end-chamber. Development of an empirical end-correction expression in a flow-reversal circular end-chamber with offset inlet and outlet ports is a practically useful contribution of this work.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1650004"},"PeriodicalIF":0.0,"publicationDate":"2016-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500041","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64077508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-14DOI: 10.1142/S0218396X16500144
N. Grigorieva, M. Kupriyanov, D. Stepanova, D. B. Ostrovskiy, I. Seleznev
The paper is devoted to modeling of the backscattered field from a spherical target immersed in a homogeneous waveguide covered with ice. A bottom of the waveguide and an ice cover are fluid, attenuating half-spaces. A target is assumed to be acoustically rigid or fluid. In particular, the properties of the ice cover and a scatterer may coincide. The emitted signal is a pulse with a Gaussian envelope. The normal mode evaluation is applied to the scattering coefficients of a sphere. The amount of normal modes forming the backscattered field is determined by a given directivity of the source. Computational results are obtained in a wide frequency range 8–12kHz for water depths equal to several hundreds of meters, and distances between a source/receiver and a target from 1km up to 10km. It is shown that in a range interval up to several kilometers the backscattered field can be calculated also using a simplified medium model consisting of a water half-space and an ice half-space. In this case the scattering coefficients of a sphere are evaluated by the steepest descent method. For the considered oceanic waveguide of 200m depth with a sandy bottom the use of the simplified medium model essentially shortens a computing time.
{"title":"Pulse Scattering on an Ice Sphere Submerged in a Homogeneous Waveguide Covered with Ice","authors":"N. Grigorieva, M. Kupriyanov, D. Stepanova, D. B. Ostrovskiy, I. Seleznev","doi":"10.1142/S0218396X16500144","DOIUrl":"https://doi.org/10.1142/S0218396X16500144","url":null,"abstract":"The paper is devoted to modeling of the backscattered field from a spherical target immersed in a homogeneous waveguide covered with ice. A bottom of the waveguide and an ice cover are fluid, attenuating half-spaces. A target is assumed to be acoustically rigid or fluid. In particular, the properties of the ice cover and a scatterer may coincide. The emitted signal is a pulse with a Gaussian envelope. The normal mode evaluation is applied to the scattering coefficients of a sphere. The amount of normal modes forming the backscattered field is determined by a given directivity of the source. Computational results are obtained in a wide frequency range 8–12kHz for water depths equal to several hundreds of meters, and distances between a source/receiver and a target from 1km up to 10km. It is shown that in a range interval up to several kilometers the backscattered field can be calculated also using a simplified medium model consisting of a water half-space and an ice half-space. In this case the scattering coefficients of a sphere are evaluated by the steepest descent method. For the considered oceanic waveguide of 200m depth with a sandy bottom the use of the simplified medium model essentially shortens a computing time.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1650014"},"PeriodicalIF":0.0,"publicationDate":"2016-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X16500144","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64078006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-22DOI: 10.1142/S0218396X15500198
Chunmei Yang, Wenyu Luo, Renhe Zhang, L. Lyu, F. Qiao
The direct-global-matrix coupled-mode model (DGMCM) for sound propagation in range-dependent waveguides was recently developed by Luo et al. [A numerically stable coupled-mode formulation for acoustic propagation in range-dependent waveguides, Sci. China G: Phys. Mech. Astron.55 (2012) 572–588]. A brief review of the formulation and characteristics of this model is given. This paper extends this model to deal with realistic problems involving an inhomogeneous water column and a penetrable sloping bottom. To this end, the normal mode model KRAKEN is adopted to provide local modal solutions and their associated coupling matrices. As a result, the extended DGMCM model is capable of providing full two-way solutions to two-dimensional (2D) realistic problems with a depth- and range-dependent sound speed profile as well as a penetrable sloping bottom. To validate this model, it is first applied to a benchmark problem of sound propagation in a plane-parallel waveguide with a depth- and range-dependent sound speed profile, and then it is applied to a problem involving both an inhomogeneous water column and a sloping bottom. Comparisons with the analytical solution proposed by DeSanto and with the numerical model COUPLE are also provided, which show that the extended DGMCM model is accurate and efficient and hence can serve as a benchmark for realistic problems of sound propagation in an inhomogeneous waveguide.
{"title":"An Efficient Coupled-Mode Formulation for Acoustic Propagation in Inhomogeneous Waveguides","authors":"Chunmei Yang, Wenyu Luo, Renhe Zhang, L. Lyu, F. Qiao","doi":"10.1142/S0218396X15500198","DOIUrl":"https://doi.org/10.1142/S0218396X15500198","url":null,"abstract":"The direct-global-matrix coupled-mode model (DGMCM) for sound propagation in range-dependent waveguides was recently developed by Luo et al. [A numerically stable coupled-mode formulation for acoustic propagation in range-dependent waveguides, Sci. China G: Phys. Mech. Astron.55 (2012) 572–588]. A brief review of the formulation and characteristics of this model is given. This paper extends this model to deal with realistic problems involving an inhomogeneous water column and a penetrable sloping bottom. To this end, the normal mode model KRAKEN is adopted to provide local modal solutions and their associated coupling matrices. As a result, the extended DGMCM model is capable of providing full two-way solutions to two-dimensional (2D) realistic problems with a depth- and range-dependent sound speed profile as well as a penetrable sloping bottom. To validate this model, it is first applied to a benchmark problem of sound propagation in a plane-parallel waveguide with a depth- and range-dependent sound speed profile, and then it is applied to a problem involving both an inhomogeneous water column and a sloping bottom. Comparisons with the analytical solution proposed by DeSanto and with the numerical model COUPLE are also provided, which show that the extended DGMCM model is accurate and efficient and hence can serve as a benchmark for realistic problems of sound propagation in an inhomogeneous waveguide.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"24 1","pages":"1550019"},"PeriodicalIF":0.0,"publicationDate":"2016-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X15500198","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64076795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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