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Eatock R Taylor - One of the best experts on this subject based on the ideXlab platform.
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water Wave Diffraction by a cylinder array part 1 regular Waves
Journal of Fluid Mechanics, 2001Co-Authors: C O G Ohl, Eatock R Taylor, P H Taylor, Alistair G L BorthwickAbstract:Diffraction of irregular Waves, focused Wave groups, and random seas by an array of vertical bottom-mounted circular cylinders is investigated using theoretical, computational and experimental methods. This is an extension of our study of such an array in regular Waves, reported in Part 1. Linear focused Wave group theory is reviewed as a method for predicting the probable shape of extreme events from random Wave spectra. Measurements are presented of the free surface elevation distribution in the vicinity of a multi-column structure in an offshore basin when subjected to irregular Waves having peak frequencies and significant Wave heights in the range 0.449 < kpa < 0.555 and 0.114 < Hs < 0.124 respectively, where a is the cylinder radius. Analytical linear Diffraction theory is extended for application to focused Wave groups and random seas. Experimental irregular Wave data are analysed for comparison with this theory. Linear Diffraction theory for random seas is shown to give an excellent prediction of incident Wave spectral Diffraction, while linear Diffraction theory for focused Wave groups works well for linearized extreme events. Due to the phase shifting of incident Wave spectral components, Diffraction is shown to generate focused Wave groups in the vicinity of the cylinder array.
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second order Wave Diffraction by an axisymmetric body in monochromatic Waves
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 1997Co-Authors: Eatock R Taylor, J B HuangAbstract:An analysis is given for the Diffraction of a plane monochromatic incident gravity Wave by an axisymmetric structure. The formulation is exact to second order in the sense of a Stokes expansion where Wave steepness is the perturbation parameter. The problem is defined in terms of the second–order velocity potential which satisfies Laplace9s equation in the fluid domain and appropriate boundary conditions. In finding the complete solution, we have decomposed the velocity potential into a particular ‘locked–Wave’ component and a ‘free–Wave’ component, which satisfy the inhomogeneous and homogeneous free–surface conditions, respectively. Special attention has been paid to finding a particular locked–Wave component that exactly satisfies the inhomogeneous free–surface condition, this inhomogeneity being a distinguishing feature of the second order problem. A semi–analytical expression for the particular component of the second–order Diffraction potential has been derived. The homogeneous component of the second–order potential is obtained by solving a boundary integral equation, using a ring–source approach. Numerical results are given for several types of fixed bodies.
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semi analytical solution for second order Wave Diffraction by a truncated circular cylinder in monochromatic Waves
Journal of Fluid Mechanics, 1996Co-Authors: J B Huang, Eatock R TaylorAbstract:A complete semi-analytical solution is given for second-order Diffraction of monochromatic Waves by a truncated vertical circular cylinder in water of uniform finite depth. The methodology presented in detail elsewhere (Eatock Taylor & Huang 1996) is adopted to find a particular solution which exactly satisfies the governing equation, the inhomogeneous free-surface condition and the seabed condition. In order to satisfy the boundary condition on the cylinder bottom, the fluid domain around the cylinder is divided into two regions. First- and second-order velocity potentials are described separately in the two regions and matched on the interface by the pressure and normal-velocity continuity conditions. Based on the formulation, the second-order Wave field in the vicinity of the cylinder and the corresponding Wave forces and overturning moments on the cylinder are studied in detail. Numerical results for the double frequency forces obtained by using the present semi-analytical approach are compared with those computed with a higher-order boundary element method (Eatock Taylor & Chau 1992). As well as the exact solution, an approximate solution is also given for the second-order potential and the corresponding forces. Numerical results show that the approximate solution possesses excellent accuracy for the total second-order heave force over a wide range of conditions. When kb > 1.2 (where k, b are the incident Wavenumber and the draught of the cylinder respectively), the accuracy for total second-order surge force and pitch moment is also satisfactory. These results could lead to the development of very efficient solutions and corresponding algorithms for the analysis of second-order Wave Diffraction by more complicated structures such as tension leg platforms. Numerical results based on the present solution show that in many cases, both the first- and the second-order-free surface elevation in the vicinity of a truncated cylinder is very close to that of a bottom-seated cylinder. For Waves with larger amplitudes, the maximum free-surface elevation around a vertical cylinder predicted with the second-order theory can significantly exceed that given by linear theory. There is also a considerable difference in the location of the maximum elevation predicted by the linear and nonlinear theories.
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new higher order boundary element methods for Wave Diffraction radiation
Applied Ocean Research, 1995Co-Authors: Bin Teng, Eatock R TaylorAbstract:This paper describes some higher-order boundary element methods and presents a novel integral equation for the calculation of the Wave Diffraction and radiation problem. A higher-order element discretisation of the resulting integral equation is used. An examination of the convergence and CPU time is carried out, and the results demonstrate the advantages of the new method.
I. M. Fuks - One of the best experts on this subject based on the ideXlab platform.
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Wave Diffraction by a rough boundary of an arbitrary plane-layered medium
IEEE Transactions on Antennas and Propagation, 2001Co-Authors: I. M. FuksAbstract:The problem of electromagnetic (EM) Wave scattering by a slightly rough boundary of an arbitrary, layered medium is solved by a small perturdation method, The bistatic amplitude of scattering as well as scattering cross sections for statistically rough surface are calculated for linear and circular polarized Waves. Along with the scattering into the upgoing Waves in the homogeneous medium, the scattering cross sections in the downgoing Waves into a layered medium are obtained, Analytical results are applied to the modeling of natural, layered media (ice and sand layers) remote sensing problems employing global position system (GPS) technics.
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Wave Diffraction by rough interfaces in an arbitrary plane-layered medium
Waves in Random Media, 2000Co-Authors: I. M. Fuks, Alexander G VoronovichAbstract:Abstract The problem of electromagnetic Wave scattering by a slightly rough interface in an arbitrarily layered medium is solved by a small-perturbation method. The bistatic amplitude of scattering as well as the scattering cross sections for statistically rough surfaces are calculated for linear polarized Waves. Along with scattering into up-going Waves in a homogeneous medium and scattering cross sections in down-going Waves into a layered medium, scattering amplitudes from a rough interface in the arbitrarily layered medium are obtained.
Ryoichi Sato - One of the best experts on this subject based on the ideXlab platform.
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Hybrid Ray-Mode Analysis of E-Polarized Plane Wave Diffraction by a Thick Slit
IEEE Transactions on Antennas and Propagation, 2016Co-Authors: Hiroshi Shirai, Masayuki Shimizu, Ryoichi SatoAbstract:A high-frequency asymptotic method has been applied to formulate E-polarized plane Wave Diffraction by a thick slit. The slit structure is regarded as an open-ended parallel plane Waveguide cavity, and the excitation of the Waveguide modes and their reradiation are derived from a ray-mode conversion technique. Comparison with another method reveals the validity and effectiveness of our formulation.
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e polarized plane Wave Diffraction by a wide and thick slit
IEEE Antennas and Propagation Society International Symposium, 2014Co-Authors: Hajime Hasegawa, Hiroshi Shirai, Ryoichi SatoAbstract:E polarized electromagnetic plane Wave Diffraction by a wide and thick slit has been analyzed by the high frequency asymptotic method. Ray-mode coupling conversion has been utilized, and the total diffracted field is considered as a summation of successive modal radiation contribution from the slit aperture due to the original modal excitation by the incident plane Wave. The derived results are compared those by the other method.
J Homer - One of the best experts on this subject based on the ideXlab platform.
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a computer simulation study of imaging flexural inhomogeneities using plate Wave Diffraction tomography
Ultrasonics, 2008Co-Authors: A Rohde, M Veidt, L R F Rose, J HomerAbstract:This paper investigates the feasibility of plate-Wave Diffraction tomography for the reconstruction of flexural inhomogeneities in plates using the results of computer simulation studies. The numerical implementation of the fundamental reconstruction algorithm, which has recently been developed by Wang and Rose [C.H. Wang, L.R.F. Rose, Plate-Wave Diffraction tomography for structural health monitoring, Rev. Quant. Nondestr. Eval. 22 (2003) 1615–1622] is investigated addressing the essential effects of applying the discrete form of the Fourier Diffraction theorem for solving the inverse problem as discussed by Kak and Slaney [A.C. Kak, M. Slaney, Principles of Computerized Tomographic Imaging, IEEE Press, New York, 1988] for the acoustic case, viz. Diffraction limited sensitivity, influence of weak scatterer assumption, damage location and scatter field data processing in time and Fourier space as well as experimental limitations such as finite receiver length and limited views. The feasibility of the imaging technique is investigated for cylindrical inhomogeneities of various severities and relative position within the interrogation space and a normal incident interrogation configuration. The results show that plate-Wave Diffraction tomography enables the quantitative reconstruction of location, size and severity of plate damage with excellent sensitivity and offers the potential for detecting corrosion thinning, disbonds and delamination damage in structural integrity management applications.
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imaging flexural inhomogeneities using plate Wave Diffraction tomography
Review of Progress in Quantitative Nondestructive Evaluation Vols 26A and 26B, 2007Co-Authors: A Rohde, M Veidt, L R F Rose, J HomerAbstract:This paper presents the first experimental implementation of plate‐Wave Diffraction tomography for the quantitative evaluation of laminar damage in plates using normal incidence inspection. The technique is investigated for origin centered, cylindrical bonded‐mass of various size and severity. The results show that Diffraction tomography using Lamb Waves and Mindlin plate theory offers excellent sensitivity and has the potential for detecting corrosion thinning, disbonds and delamination damage in structural integrity management applications.
Pleshchinskii N. - One of the best experts on this subject based on the ideXlab platform.
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Parallel algorithm of solving the electromagnetic Wave Diffraction problem on the spherical screen
2020Co-Authors: Karchevskiy E., Pleshchinskii N.Abstract:The electromagnetic Wave Diffraction problem on a thin conducting spherical screen is reduced to pair summatorial equation relative to unknown coefficients of expansion into a series of spherical Waves. This equation can be transformed to a regular infinite set of linear algebraic equations by integral-summatorial identities method. For all stages of numerical algorithm of solving the problem the parallel calculating processes are possible. At first, if field traces of outside source at the sphere are decomposed onto magnetic and electric parts, then magnetic and electric parts of the unknown field can be found independently. Secondly, if coefficients of field conjugation conditions at the sphere do not depend on longitude coordinate, then calculations also can be fulfilled independently for every number of the series coefficients. Thirdly, if by reduction of infinite set the finite set of linear equations of large dimension is obtained, then it can be solved by one of parallel algorithms. But the most effect can be obtained just at the stage of calculating the auxiliary integrals over screen
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Wave Diffraction problems on periodical sets of heterogeneities in the stratified media
2020Co-Authors: Osipov E., Pleshchinskii N., Rogozhin P.Abstract:The universal approach to solving the Diffraction problems on the periodical set of heterogeneities in the stratified media is proposed. The infinite periodic grating consisting of thin conducting bands embedded into a dielectric plate is considered as an example. The boundary value problem for the quasi-periodic potential functions is equivalent to the pair summatorial functional equation for the Floquet coefficients. At first, it is advisable to solve the auxiliary Diffraction problem for the stratified medium in the case when the heterogeneities are moved off. The heterogeneities generate the field perturbation; it is a solution of a similar pair equation. Secondly, we need to define new unknown variables in such way that the pair equation should have the standard form. To get this result we propose to use the boundary value conditions on the heterogeneities. Then the other conditions on the media interface can be transformed to standard form. The dual equation is equivalent to regular infinite set of linear algebraic equations for the coefficients of decomposition of the electromagnetic field by Floquet harmonics. In the case of elastic Waves the Wave Diffraction problems on the periodical sets of heterogeneities can be reduced to vector dual summatorial functional equations. The electromagnetic Wave Diffraction problems on the periodical knife grating was investigated by analogous scheme
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On problems of electromagnetic Wave Diffraction on periodical sets of heterogeneities in the layered media
2020Co-Authors: Osipov E., Pleshchinskii N., Rogozhin P.Abstract:The universal approach to solving the Diffraction problems on the periodical set of heterogeneities in the layered media is proposed. The infinite periodic grating consisting of thin conducting bands embedded into a dielectric plate is considered as an example. At first, it is advisable to solve the auxiliary Diffraction problem in the case when the heterogeneities are moved off. The heterogeneities generate the field perturbation; it is a solution of a similar pair equation. Secondly, we need to define new unknown variables in such way that the pair equation should have the standard form. To get this result we propose to use the boundary value conditions on the heterogeneities. The dual equation is equivalent to regular infinite set of linear equations for the Floquet coefficients. In some case the Wave Diffraction problems on the periodical sets of heterogeneities can be reduced to vector dual summatorial functional equations. © 2012 IEEE
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The over-determined boundary value problems for the maxwell equations set in the orthogonal coordinates and some applications for the electromagnetic Wave Diffraction problems
2020Co-Authors: Pleshchinskii N.Abstract:The necessary and sufficient conditions of solvability of the over-determined problems for the Maxwell equations set are obtained in the cases of Cartesian, cylindrical and spherical coordinates. These conditions are used by reduction of the electromagnetic Wave Diffraction problems on the thin conducting screen placed on the coordinate surfaces to integral or summatorial equations. Moreover, these conditions can be used for regularization of the integral equations of the first kind obtained by solving the Diffraction problems. In the case on three-dimensional problems of electrodynamics the over-determined problems appear when both the tangential components of the electric vector and of the magnetic vector are given on the boundary of the partial domains. It is shown that the conditions of solvability of the over-determined problems can be obtained in the different form. The common form is the dependence of the Fourier transforms or Fourier coefficients of the boundary functions. But the mixed form is possible when both expressions participate. The set of the three-dimensional Diffraction problems on the thin conducting screens in the Wave-guided structures is considered as examples
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Diffraction on the eigenWaves on an inclined medium interface in the Waveguides with metallic bounds
2020Co-Authors: Pleshchinskii N.Abstract:© 2002 IEEE. The electromagnetic Wave Diffraction problems on an inclined medium interface with a metallic plate and without it in the plane Waveguide and in the rectangular Waveguide are considered. It is shown that these problems can be reduced to boundary value problems for the Helmholtz equation or for the Maxwell system in a bounded rectangular domain
