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Wave Diffraction (wave + diffraction)

Distribution by Scientific Domains

Engineering	57%
Mathematics and Statistics	42%

Selected Abstracts

Wave diffraction by a strip grating: the two-straight line approach

MATHEMATISCHE NACHRICHTEN, Issue 1 2004
M. A. Bastos
Abstract Boundary-value problems of wave diffraction by a periodic strip grating are associated with a Toeplitz operator acting on a space of functions defined on a two-straight line contour. Simple formulas are given for the left inverse of the operator associated with the Neumann boundary-value problem and for the right inverse of the operator associated with the Dirichlet boundary-value problem when the period of the grating is equal to double the width of the strips. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Two-dimensional anisotropic Cartesian mesh adaptation for the compressible Euler equations

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2004
W. A. Keats
Abstract Simulating transient compressible flows involving shock waves presents challenges to the CFD practitioner in terms of the mesh quality required to resolve discontinuities and prevent smearing. This paper discusses a novel two-dimensional Cartesian anisotropic mesh adaptation technique implemented for transient compressible flow. This technique, originally developed for laminar incompressible flow, is efficient because it refines and coarsens cells using criteria that consider the solution in each of the cardinal directions separately. In this paper, the method will be applied to compressible flow. The procedure shows promise in its ability to deliver good quality solutions while achieving computational savings. Transient shock wave diffraction over a backward step and shock reflection over a forward step are considered as test cases because they demonstrate that the quality of the solution can be maintained as the mesh is refined and coarsened in time. The data structure is explained in relation to the computational mesh, and the object-oriented design and implementation of the code is presented. Refinement and coarsening algorithms are outlined. Computational savings over uniform and isotropic mesh approaches are shown to be significant. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Absorbing boundary condition on elliptic boundary for finite element analysis of water wave diffraction by large elongated bodies

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2001
Subrata Kumar Bhattacharyya
Abstract In a domain method of solution of exterior scalar wave equation, the radiation condition needs to be imposed on a truncation boundary of the modelling domain. The Bayliss, Gunzberger and Turkel (BGT) boundary dampers of first- and second-orders, which require a circular cylindrical truncation boundary in the diffraction-radiation problem of water waves, have been particularly successful in this task. However, for an elongated body, an elliptic cylindrical truncation boundary has the potential to reduce the modelling domain and hence the computational effort. Grote and Keller [On non-reflecting boundary conditions. Journal of Computational Physics 1995; 122: 231,243] proposed extension of the first- and second-order BGT dampers for the elliptic radiation boundary and used these conditions to the acoustic scattering by an elliptic scatterer using the finite difference method. In this paper, these conditions are implemented for the problem of diffraction of water waves using the finite element method. Also, it is shown that the proposed extension works well only for head-on wave incidence. To remedy this, two new elliptic dampers are proposed, one for beam-on incidence and the other for general wave incidence. The performance of all the three dampers is studied using a numerical example of diffraction by an elliptic cylinder. Copyright © 2001 John Wiley & Sons, Ltd. [source]

On wave diffraction by a half-plane with different face impedances

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 5 2007
L. P. Castro
Abstract The impedance wave diffraction problem by a half-plane screen is revisited in view of its well-posedness upon different impedance and wave parameters. The problem is analysed with the help of potential and pseudo-differential operators. Seven conditions between the impedance and wave numbers are found under which the problem will be well-posed in Bessel potential spaces. In addition, an improvement of the regularity of the solutions is shown for the previous seven conditions. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Wave diffraction by a strip grating: the two-straight line approach

Analytical solution of the harmonic waves diffraction by a cylindrical lined cavity in poroelastic saturated medium

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2007
Y. S. Karinski
Abstract This paper presents a model for the analysis of plane waves diffraction at a cavity in an infinite homogeneous poroelastic saturated medium, lined by a lining composed of four equal segments. An elastic boundary layer is placed between the cavity lining and the infinite porous medium. The boundary layer is simulated by ,elastic boundary conditions' in which the bulk matrix stress is proportional to the relative displacement between the lining and the surrounding medium matrix boundary. In addition, fluid impermeability through the intermediate layer is assumed. For the frequencies, that differ from the pseudoresonanse frequencies, the problem was reduced to the problem of an ideal elastic medium. A closed-form analytical solution of the problem was obtained using Fourier,Bessel series, the convergence of which was proven. It was shown that the number of series terms required to obtain a desired level of accuracy can be determined in advance. The influence of the medium porosity on the medium dynamic stress concentration was studied. Copyright © 2006 John Wiley & Sons, Ltd. [source]