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Wyszukujesz frazę "acoustic scattering" wg kryterium: Temat

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    Wyświetlanie 1-12 z 12
    Tytuł:
    Acoustic Scattering of 3D Complex Systems Having Random Rough Surfaces by Scalar Integral Equations
    Autorzy:
    Guel-Tapia, J. A.
    Villa-Villa, F.
    Mendoza-Suárez, A.
    Pérez-Aguilar, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/178120.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    integral equations
    Helmholtz equation
    acoustic scattering
    Opis:
    We propose a numerical surface integral method to study complex acoustic systems, for interior and exterior problems. The method is based on a parametric representation in terms of the arc’s lengths in curvilinear orthogonal coordinates. With this method, any geometry that involves quadric or higher order surfaces, irregular objects or even randomly rough surfaces can be considered. In order to validate the method, the modes in cubic, spherical and cylindrical cavities are calculated and compared to analytical results, which produced very good agreement. In addition, as examples, we calculated the scattering in the far field and the near field by an acoustic sphere and a cylindrical structure with a rough cross-section.
    Źródło:
    Archives of Acoustics; 2016, 41, 3; 461-472
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling materials with desired refractive index
    Autorzy:
    Andriychuk, Mykhaylo
    Marikutsa, Uliana
    Powiązania:
    https://bibliotekanauki.pl/chapters/32304267.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
    Tematy:
    refractive index
    acoustic scattering
    numerical calculations
    Opis:
    The explicit solution to the diffraction problem on a set of small particles, supplemented into homogeneous material, is used for modeling the materials with the desired refractive index. The consideration concerns to the case of acoustic scalar scattering and the solution to initial scattering problem is built using an asymptotic approach. The closed form solution is reduced for the scattering problem. This lets an explicit formula for the refractive index of the resulting inhomogeneous material to be obtained. The numerical calculations show the possibility of getting the specific values of refractive index including its negative values.
    Źródło:
    Methods and tools in CAD – selected issues; 87-98
    9788366391871
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Adaptive boundary element method for acoustic scattering problems
    Adaptacyjna metoda elementów brzegowych w zadaniu rozpraszania fali akustycznej
    Autorzy:
    Karafiat, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/281228.pdf
    Data publikacji:
    1998
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    boundary element method
    adaptive methods
    acoustic scattering
    Opis:
    The subject of the paper is an application of the boundary element method to problems of scattering of acoustic waves by an elastic solid submerged in a fluid. A model problem of linear acoustics with a simplified fluid-solid interaction on the boundary is considered. The problem is described by the Burton-Miller integral equation. The Galerkin method is used to obtain an approximate solution. Adaptive methods of approximation are discussed. Some a posteriori error estimates are given.
    Przedmiotem pracy jest zastosowanie metody elementów brzegowych do zadania rozpraszania fali akustycznej w płynie przez zanurzone w niej ciało sprężyste. Przyjmuje się postulaty liniowej akustyki i teorii sprężystości i uproszczony model interakcji ciała stałego i płynu. Do rozwiązania zadania stosuje się wariacyjne sformułowanie równania całkowego Burtona-Millera, rozwiązywane w sposób przybliżony za pomocą metody Galerkina. W pracy omówiono w skrócie zastosowanie metody elementów brzegowych z różnymi rodzajami adaptacji do aproksymacji rozwiązania, modelowania brzegu i całkowania numerycznego. Podano także najczęściej stosowane metody szacowania błędu a posteriori.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 1998, 2; 423-436
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modulation Mechanism of Acoustic Scattering in Underwater Corner Reflectors with Acoustic Metasurfaces
    Autorzy:
    Du, Jiaman
    Peng, Zilong
    Ge, Lili
    Lyu, Shijin
    Zhou, Fulin
    Liu, Yan
    Powiązania:
    https://bibliotekanauki.pl/articles/31339794.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    acoustic scattering
    metasurface
    ray tracing
    corner reflector
    virtual source method
    Opis:
    Using the tunderwater corner reflector (CR) to simulate the acoustic scattering characteristics of the military target is a new technology to counter active sonar detection. Existing underwater CRs only have the ability to interfere with the acoustic field, but have limitations in acoustic wave modulation. Therefore, acoustic metasurfaces applied on CRs to enhance the ability of acoustic wave modulation has a great application prospect. A fast prediction method based on the Kirchhoff approximation (KA) and the ray tracing theory is proposed to calculate the acoustic scattering characteristics of CR with acoustic metasurfaces in grooves array type. The accuracy of the method is verified by the finite element method (FEM) simulation. The modulation effect of CR with grooves array in different gradient combinations on the structural scattering acoustic field is analyzed. The research shows that the CR with different combinations of the acoustic metasurface has an obvious modulation effect on the amplitude of the acoustic waves and the deflection of acoustic field. In particular, the grooves array in combination with positive and negative gradients has an obvious deflection impact on the scattering acoustic field.
    Źródło:
    Archives of Acoustics; 2023, 48, 4; 465-473
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On some elliptic transmission problems
    Autorzy:
    Athanasiadis, Christodoulos
    Stratis, Ioannis
    Powiązania:
    https://bibliotekanauki.pl/articles/1311187.pdf
    Data publikacji:
    1996
    Wydawca:
    Polska Akademia Nauk. Instytut Matematyczny PAN
    Tematy:
    transmission condition
    Dirichlet problem
    Robin problem
    diffraction problem
    acoustic scattering
    Opis:
    Boundary value problems for second order linear elliptic equations with coefficients having discontinuities of the first kind on an infinite number of smooth surfaces are studied. Existence, uniqueness and regularity results are furnished for the diffraction problem in such a bounded domain, and for the corresponding transmission problem in all of $ℝ^N$. The transmission problem corresponding to the scattering of acoustic plane waves by an infinitely stratified scatterer, consisting of layers with physically different materials, is also studied.
    Źródło:
    Annales Polonici Mathematici; 1996, 63, 2; 137-154
    0066-2216
    Pojawia się w:
    Annales Polonici Mathematici
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Isogeometric Fast Multipole Boundary Element Method Based on Burton-Miller Formulation for 3D Acoustic Problems
    Autorzy:
    Chen, Leilei
    Zhao, Wenchang
    Liu, Cheng
    Chen, Haibo
    Marburg, Steffen
    Powiązania:
    https://bibliotekanauki.pl/articles/177486.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    isogeometric analysis
    boundary element method
    Burton-Miller method
    acoustic scattering
    fast multipole method
    Opis:
    An isogeometric boundary element method is applied to simulate wave scattering problems governed by the Helmholtz equation. The NURBS (non-uniform rational B-splines) widely used in the CAD (computer aided design) field is applied to represent the geometric model and approximate physical field variables. The Burton-Miller formulation is used to overcome the fictitious frequency problem when using a single Helmholtz boundary integral equation for exterior boundary-value problems. The singular integrals existing in Burton-Miller formulation are evaluated directly and accurately using Hadamard’s finite part integration. Fast multipole method is applied to accelerate the solution of the system of equations. It is demonstrated that the isogeometric boundary element method based on NURBS performs better than the conventional approach based on Lagrange basis functions in terms of accuracy, and the use of the fast multipole method both retains the accuracy for isogeometric boundary element method and reduces the computational cost.
    Źródło:
    Archives of Acoustics; 2019, 44, 3; 475-492
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Research on the modified echo highlight model for underwater vehicles with combined structures
    Autorzy:
    Xie, Xin
    Liu, Fanghua
    Jin, Guangwen
    Liu, Jinwei
    Xu, Cong
    Peng, Zilong
    Powiązania:
    https://bibliotekanauki.pl/articles/34609383.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    modified highlight model
    wedge-shaped convex structure
    piecewise synthesis method
    acoustic scattering calculation software
    Opis:
    The highlight model is widely used as a simple and convenient method in the radar field but its accuracy is not high. Based on the traditional highlight model, the algorithm has been improved to address the acoustic scattering problems of underwater vehicles with more complex line shapes. The basic idea is to partition the model into micro-bodies to calculate the scattered sound pressure, consider the phase interference of each part, and then synthesise the scattered sound pressure to approximate the target’s actual shape. A computational model of the wedge-shaped convex structure on the back of the underwater vehicles is developed using a highlight model of a trapezoidal plate. The results of the calculations using the highlight model approach are consistent with those of the planar element method. Utilising the modified highlight model method, the accuracy of acoustic scattering characteristics calculations for the stern and overall structures of underwater vehicles has proven satisfactory. Finally, fast acoustic scattering prediction software is developed for underwater vehicles, enabling the calculation of the acoustic scattering characteristics for individual structures, combined structures, and coated silent tiles. This software provides algorithmic support for the fast prediction of the acoustic stealth performance of underwater vehicles.
    Źródło:
    Polish Maritime Research; 2023, 3; 163-173
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Design, Manufacture and Characterization of an Acoustic Barrier Made of Multi-Phenomena Cylindrical Scatterers Arranged in a Fractal-Based Geometry
    Autorzy:
    Casteneira-Ibanez, S.
    Rubio, C.
    Romero-Garcia, V.
    Sanchez-Perez, J. V.
    Garcia-Raffi, L. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/176662.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    acoustic arrays
    acoustic attenuation
    acoustic wave absorption
    acoustic wave scattering
    phononic crystals
    acoustic barrier
    physical effect of sound
    Opis:
    In this work we present the design and the manufacturing processes, as well as the acoustics standard- ization tests, of an acoustic barrier formed by a set of multi-phenomena cylindrical scatterers. Periodic arrangements of acoustic scatterers embedded in a fluid medium with different physical properties are usually called Sonic Crystals. The multiple scattering of waves inside these structures leads to attenuation bands related to the periodicity of the structure by means of Bragg scattering. In order to design the acoustic barrier, two strategies have been used: First, the arrangement of scatterers is based on fractal geometries to maximize the Bragg scattering; second, multi-phenomena scatterers with several noise con- trol mechanisms, as resonances or absorption, are designed and used to construct the periodic array. The acoustic barrier reported in this work provides a high technological solution in the field of noise control.
    Źródło:
    Archives of Acoustics; 2012, 37, 4; 455-462
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Detection of wavy sea surface oil-derivative contamination with forward specular high-frequency scattering
    Autorzy:
    Pogorzelski, Stanisław
    Rochowski, Paweł
    Grzegorczyk, Maciej
    Linde, Bogumił B. J.
    Skrodzka, Ewa
    Bielasiewicz, Łukasz
    Powiązania:
    https://bibliotekanauki.pl/articles/260616.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    crude oil contamination
    capillary wave damping
    acoustic surface scattering
    statistical-frequency analyses
    at-sea pollution detection
    Opis:
    A spectrum of low-frequency (20‒30 Hz) amplitude fluctuations of the ultrasonic (10 MHz) signal specularly scattered from water surfaces covered with monomolecular and thicker crude oil origin films of well-defined, oceanographically relevant viscoelastic properties was examined in laboratory and at-sea conditions. The relationship between the Surface water wave (30 Hz) damping coefficient and the oil layer thickness was established, and compared to the one predicted by the classical Stokes theory. The depression of the spectral energy density of wind-driven waves by surface films was inferred from the ratio of acoustic signal fluctuations spectra with/without films, and compared to that resulting from the Marangoni damping theory applicable to monolayers of particular surface viscoelasticity. The agreement between the theory and experimental data was satisfactory. As shown in at-sea experiments performed with a free-floating, buoy-like acoustic system, and an artificial oil slick spread over the Baltic Sea surface, the film’s rheological Surface properties can be recovered from acoustic surface probing, as well as oil spill edge detection. Simultaneous statistical analyses of the scattered signal amplitude distribution parameters turned out to be unequivocally related to the oil substance fraction weight, oil layer thickness, and the form of oil contamination.
    Źródło:
    Polish Maritime Research; 2020, 1; 173-179
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Identification of Physical Parameters of a Porous Material Located in a Duct by Inverse Methods
    Autorzy:
    Kani, Marwa
    Makni, Amine
    Taktak, Mohamed
    Chaabane, Mabrouk
    Haddar, Mohamed
    Powiązania:
    https://bibliotekanauki.pl/articles/2141708.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    porous materials
    inverse methods
    scattering matrix
    acoustic power attenuation
    Opis:
    Lined ducts with porous materials are found in many industrial applications. To understand and simulate the acoustic behaviour of these kinds of materials, their intrinsic physical parameters must be identified. Recent studies have shown the reliability of the inverse approach for the determination of these parameters. Therefore, in the present paper, two inverse techniques are proposed: the first is the multilevel identification method based on the simplex optimisation algorithm and the second one is based on the genetic algorithm. These methods are used of the physical parameters of a simulated case of a porous material located in a duct by the computation of its acoustic transfer, scattering, and power attenuation. The results obtained by these methods are compared and discussed to choose the more efficient one.
    Źródło:
    Archives of Acoustics; 2021, 46, 4; 657-665
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation on the Effects of Acoustic Liner Variation and Geometry Discontinuities on the Acoustic Performance of Lined Ducts
    Autorzy:
    Dhief, Raja
    Makni, Amine
    Taktak, Mohamed
    Chaabane, Mabrouk
    Haddar, Mohamed
    Powiązania:
    https://bibliotekanauki.pl/articles/177513.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    absorbent systems effect
    discontinuities effect
    scattering matrix
    acoustic power attenuation
    Opis:
    Noise reduction inside waveguide systems has gained momentum owing to a great interest in it. To attenuate the sound in a broad frequency range, this study aims to compare the effects of two acoustic liners, a perforated plate backed by an air cavity (PP-Air cavity), or by a porous material (PP-PM), on the acoustic behaviour of lined ducts using a numerical model to compute the multimodal scattering matrix. From this matrix, the reflection and the transmission coefficients are computed and therefore the acoustic power attenuation is deduced. Moreover, the effects of geometry of ducts with and without changes in the section are investigated. The numerical results are obtained for five configurations, including cases of narrowing and widening of a duct portion with sudden or progressive discontinuities. Accordingly, numerical coefficients of reflection and transmission as well as the acoustic power attenuation show the relative influence of acoustic liners in each type of configuration.
    Źródło:
    Archives of Acoustics; 2020, 45, 1; 49-66
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Liner Characteristics on the Acoustic Performance of Duct Systems
    Autorzy:
    Othmani, C.
    Hentati, T.
    Taktak, M.
    Elnady, T.
    Fakhfakh, T.
    Haddar, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/176887.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    porous material
    perforated plate
    duct system
    scattering matrix
    acoustic attenuation
    Opis:
    Porous materials are used in many vibro-acoustic applications. Different models describe their performance according to material’s intrinsic characteristics. In this paper, an evaluation of the effect of the porous and geometrical parameters of a liner on the acoustic power attenuation of an axisymmetric lined duct was performed using multimodal scattering matrix. The studied liner is composed by a porous material covered by a perforated plate. Empirical and phenomenal models are used to calculate the acoustic impedance of the studied liner. The later is used as an input to evaluate the duct attenuation. By varying the values of each parameter, its influence is observed, discussed and deduced.
    Źródło:
    Archives of Acoustics; 2015, 40, 1; 117-127
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-12 z 12

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