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Stabilized Single Current Inverse Source Formulations Based on Steklov-Poincare Mappings

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2023年第10期71卷 8158-8164页

作者： Ricci, Paolo Citraro, Ermanno Merlini, Adrien Andriulli, Francesco P. Politecn Torino Dept Elect & Telecommun I-10129 Turin Italy IMT Atlantique Microwave Dept Ecole Natl Super Mines Telecom Atlantique F-29238 Brest France

The inverse source problem in electromagnetics has proved quite relevant for a large class of applications. When it is coupled with the equivalence theorem, the sources are often evaluated as electric and/or magnetic current distributions on an appropriately chosen equivalent surface. In this context, in antenna diagnostics, in particular, Love solutions, i.e., solutions that radiate zero-fields inside the equivalent surface, are often sought at the cost of an increase of the dimension of the linear system to be solved. In this work, instead, we present a reduced-in-size single current formulation of the inverse source problem that obtains one of the Love currents via a stable discretization of the Steklov- Poincare boundary operator leveraging dual functions. The new approach is enriched by theoretical treatments and by a further low-frequency stabilization of the Steklov- Poincare operator based on the quasi-Helmholtz projectors that is the first of its (i.e., low-frequency stabilization) kind in this field. The effectiveness and practical relevance of the new schemes are demonstrated via both theoretical and numerical results.

关键词： boundary-element method inverse source problem Love currents low-frequency breakdown Steklov-Poincare operator

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THE MECHANICS OF INTERMATERIAL CRACKS WITH CONTACTING FACESUNDER SHEAR WAVE LOADING

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INTERNATIONAL APPLIED MECHANICS 2022年第4期58卷 455-463页

作者： Men'shikov, V. O. Men'shikov, O. V. Kladova, O. Yu. Natl Aerosp Univ Kharkiv Aviat Inst 17 Chkalova St UA-61070 Kharkiv Ukraine Univ Aberdeen Ctr Microand Nanomech CEMINACS Sch Engn Aberdeen AB24 UE Scotland

A nonlinear problem for an intermaterial crack (cut) under a harmonic shear wave is solved using the method of boundary integral equations. A numerical analysis is carried out to identify the features of the displacements of the intermaterial crack faces and the adjacent interface surface when the frequency of the shear wave changes. The dependence of the crack opening, the length of the contact zone of the crack faces, and the contact forces on the loading frequency.

关键词： interface crack harmonic shear wave boundary-element method contact area of crack faces contact forces

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Interfacial Crack with Frictionless and Frictional Contact of Faces in a Bimaterial under a Shear Wave

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INTERNATIONAL APPLIED MECHANICS 2022年第1期58卷 102-110页

作者： Men'shikov, V. O. Men'shikov, O., V Kladova, O. Yu Natl Aerosp Univ Kharkiv Aviat Inst 17 Chkalova St UA-61070 Kharkiv Ukraine Univ Aberdeen Ctr Micro & Nanomech CEMINACS Sch Engn Aberdeen AB24 3UE Scotland

The problem of the theory of elasticity for a bimaterial with an interface crack under a harmonic shear wave is solved numerically using the boundary-element method. The faces are considered to be in frictionless or frictional contact. The distribution of displacements of the cracks, the emerging dynamic contact areas of the faces, and contact forces is analyzed.

关键词： interface crack harmonic shear wave boundary-element method contact area of crack faces contact forces

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Collapse of Capillary-Gravitational Waves and the Generation of Cumulative Jets

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FLUID DYNAMICS 2020年第8期55卷 953-964页

作者： Baykov, N. D. Petrov, A. G. Moscow MV Lomonosov State Univ Moscow 119991 Russia Russian Acad Sci Ishlinsky Inst Problems Mech Moscow 119526 Russia

In this paper, we study plane unsteady problems of motion of a free boundary in a potential flow of an ideal incompressible fluid. A numerical algorithm for calculating the shape of the free boundary is constructed based on the boundary-element method. When deriving approximations, the boundary smoothness is taken into account. The main attention is paid to the problems of the formation of thin cumulative jets and wave breaking, as well as substantiation of the reliability of numerical calculations.

关键词： cumulative jets boundary-element method wave breaking

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UNSTEADY WAVE-MAKING RESISTANCE OF AN ACCELERATING SHIP 39

UNSTEADY WAVE-MAKING RESISTANCE OF AN ACCELERATING SHIP

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ASME 39th International Conference on Ocean, Offshore and Arctic Engineering (OMAE)

作者： Li, Mingxin Yuan, Zhi-Ming Yeung, Ronald W. Jiangsu Univ Sci & Technol Sch Naval Architecture & Ocean Engn Zhenjiang Peoples R China Univ Strathclyde Dept Naval Architecture Ocean & Marine Engn Glasgow Scotland Univ Calif Berkeley Dept Mech Engn Berkeley CA 94720 USA

ISBN: (纸本)9780791884379

To measure the resistance of a ship in a towing tank, the target speed of the ship model is achieved by towing the model from the rest at a given acceleration imposed by the carriage. The fluctuations in resistance are generated because of the impulse effects during rapid acceleration. Such acceleration effects in deep water have been studied by previous works [1-3]. In shallow water, the unsteady effects are expected to be stronger, making the fluctuating resistance persisting longer. In order to predict the unsteady waves and to estimate the unsteady oscillating components in the wave resistance, a numerical method based on 3D unsteady potential-flow theory was developed. An implicit finite-difference algorithm coupled with an iterative boundary integral-equation solution procedure was used to deal with the unsteady linear and nonlinear free-surface condition. The results showed that both the acceleration intensity and water depth have a significant effect on the oscillation amplitude of the unsteady wave resistance as well as other force components. Findings of these computations and comparative evaluation of experimental observation are made where relevant. The findings in the present work can be applied to provide guidance for using the appropriate settings, e.g., magnitude and duration of carriage acceleration, when conducting ship-model resistance tests.

关键词： Free-surface effects nonlinear free-surface conditions unsteady wave resistance boundary-element method shallow-water effects ship-model testing

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Spherical Hankel-Based Creep Analysis of Time-Dependent Materials Using boundary-element Theories

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JOURNAL OF ENGINEERING MECHANICS 2020年第6期146卷

作者： Bahrampour, M. Hamzehei-Javaran, S. Shojaee, S. Shahid Bahonar Univ Kerman Dept Civil Engn Kerman *** Iran

In this article, the boundary-element method (BEM) is applied to solve viscoelastic problems with any alteration in load, time, or boundary condition. The innovation of using spherical Hankel element framework instead of the classical Lagrangian approach is an effort to estimate the state variables of essential differential equations of BEM. This approach leads to the simultaneous satisfaction of the first- and second-order Bessel functions and the customary polynomial functions. A computer code has been generated to validate this progressive method. The results of various numerical examples, in which the analytical solution is measured and compared with Lagrangian- and Hankel-based BEM, are illustrated by means of comparative graphs. This evaluation reveals that the new method portrays much better agreement with the analytical solution in contrast to the classic BEM and maintains the accuracy while using the least degrees of freedom, indicating that it has significantly less error percentage owing to the fact that by utilizing the least number of elements, the desired precision is acquired. Thus, the current method is introduced and recommended as it is more economical and time-saving.

关键词： Spherical Hankel shape functions Radial basis functions boundary-element method 2D viscoelastic problems Kelvin's fundamental solution

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Added mass of thin flat plates of arbitrary shapes with possible openings

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APPLIED OCEAN RESEARCH 2018年 79卷 149-159页

作者： Nokob, Mohamed Hariri Yeung, Ronald W. Univ Calif Berkeley Berkeley CA 94720 USA

We present results for the added mass and moment of inertia of infinitely thin plates of arbitrary shapes in an infinite potential field. The problem is modeled using a hypersingular boundary-integral equation and is treated directly using a Galerkin approach without regularization. The results are used to fill some gaps in the literature of the values of added mass for these plates, particularly those plates with openings or holes and we compare the exact numerical results with those obtained by simply subtracting the added mass or inertia from those of the full plate (an algebraic approximation). The algebraic approximation gives incorrect values compared with actual three-dimensional results.

关键词： Thin plates Hypersingular integrals boundary-element method Added mass

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Numerical Simulation of the Potential Flow around a Submerged Hydrofoil with Fully Nonlinear Free-Surface Conditions

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JOURNAL OF COASTAL RESEARCH 2018年第1期34卷 238-252页

作者： Hu, Jian Guo, Lei Sun, Shili Harbin Engn Univ Coll Shipbldg Engn Harbin 150001 Heilongjiang Peoples R China

Hydrofoils have been utilized worldwide to facilitate coastal vessels for transportation, surveillance, and patrol with high speed. Inevitably, the free surface has a significant effect on the hydrofoils because of the shallow draft. In this paper, a numerical procedure based on a boundary-element method is developed for simulating a uniform incoming flow passing a two-dimensional submerged hydrofoil with free-surface effects. In the proposed technique, the boundaries of the computational domain are discretized by small elements over which the known and unknown variables are linearly distributed. To avoid the numerical instabilities induced by the sudden start of the flow through a sharp-edged foil, it is assumed that a vortex sheet with uniform strength C has been placed within the foil at the initial time step. The unknown vortex strength C, the velocity potential phi and phi(n) on the boundaries are obtained simultaneously by solving the boundary integral equation together with an added auxiliary function at each time step. The free surface is assumed to be undisturbed at the initial time step. Then, it is traced by a Eulerian scheme. Both linear and nonlinear free-surface conditions have been applied. Convergence studies with respect to the element size, the time step, and the size of far-field boundaries have been undertaken. Comparison of the present numerical results with experimental data and previous numerical results shows that the present method gives fairly good results on the force, circulation, and wave excitation of the foil.

关键词： Kutta condition wave excitation boundary-element method vortex sheet

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New Higher Order method of Moments for Accurate Inductance Extraction in Transmission Lines of Complex Cross Sections

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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2017年第12期65卷 5104-5112页

作者： Lori, Farhad Sheikh Hosseini Hosen, Mohammad Shakander Menshov, Anton Shafieipour, Mohammad Okhmatovski, Vladimir I. Univ Manitoba Dept Elect & Comp Engn Winnipeg MB R3T 5V6 Canada Univ Texas Austin Dept Elect & Comp Engn Austin TX 78712 USA Manitoba HVDC Res Ctr Winnipeg MB R3P 1A3 Canada

A new higher order (HO) method of moments is proposed for high accuracy extraction of the resistance and inductance matrices in the multiconductor transmission lines (MTLs) of complex cross sections. The computational framework is based on the numerical solution of a surface-volume-surface electric field integral equation of magnetostatics. In order to achieve an exponentially efficient reduction in the error of the solution, HO geometrical representation of the conductor cross sections is accompanied with the discretization of the unknown field quantities on the conductor boundaries and cross sections with 1-D and 2-D HO polynomial basis functions, respectively. The methodology allows for extraction of the network parameters in broad ranges of frequencies for which resistive and inductive contributions to the impedance matrix vary within a wide dynamic range. Comparison of numerically computed currents to the currents obtained analytically for canonical transmission line configurations is performed. Solutions of the extraction problem for MTLs with complex cross sections are compared against the finite-element method solutions to demonstrate the efficiency of the proposed methodology.

关键词： boundary-element method higher order (HO) methods integral equations integrated-circuit interconnections magnetoquasi-statics method of moments (MoM) parameter extraction

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Solution of Open-boundary Problems by Means of the Hybrid FEM-GDBCI method

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IEEE TRANSACTIONS ON MAGNETICS 2017年第6期53卷 1-4页

作者： Aiello, G. Alfonzetti, S. Rizzo, S. A. Salerno, N. Univ Catania Dipartimento Ingn Elettr Elettron & Informat I-95125 Catania Italy

In this paper, the hybrid finite-element method-Galerkin Dirichlet boundary condition iteration method is described for the finite-element solution of a variety of low-frequency electromagnetic field problems in open boundary domains. The method assumes a Dirichlet boundary condition on the truncation boundary and its imposition is made by means of a Galerkin integral equation over another surface strictly enclosed by the truncation boundary.

关键词： boundary-element method computational electromagnetics finite-element method (FEM) integral equations

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