References of "Geuzaine, Christophe"
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See detailA high-order absorbing boundary condition for 2D time-harmonic elastodynamic scattering problems
Mattesi, Vanessa ULiege; Darbas, Marion; Geuzaine, Christophe ULiege

in Computers and Mathematics with Applications (2019), 77(6), 1703-1721

In this paper, we are concerned with the construction of a new high-order Absorbing Boundary Condition (ABC) for 2D-elastic scattering problems. It is defined by an approximate local Dirichlet-to-Neumann ... [more ▼]

In this paper, we are concerned with the construction of a new high-order Absorbing Boundary Condition (ABC) for 2D-elastic scattering problems. It is defined by an approximate local Dirichlet-to-Neumann (DtN) map. First, we explain the derivation of this approximation. Next, a detailed analytical study in terms of Hankel functions in the circular case is addressed. The new ABC is compared with the standard low-order Lysmer–Kuhlemeyer ABC. Finally, its accuracy and efficiency are investigated for various numerical examples, particularly at high frequencies. [less ▲]

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See detailCombination of topology optimization and Lie derivative-based shape optimization for electro-mechanical design
Kuci, Erin ULiege; Henrotte, François ULiege; Duysinx, Pierre ULiege et al

in Structural and Multidisciplinary Optimization (2018)

Detailed reference viewed: 58 (11 ULiège)
See detailNumerical simulations of the penetration of magnetic field in a superconducting film : H-phi formulation with shell-transformation techniques
Burger, Loïc ULiege; Geuzaine, Christophe ULiege; Henrotte, François ULiege et al

Poster (2018, June 28)

We consider the Finite Element Method (FEM) to solve numerically the problem of the penetration of magnetic field applied perpendicularly to a superconducting thin film. Although theoretical boundary ... [more ▼]

We consider the Finite Element Method (FEM) to solve numerically the problem of the penetration of magnetic field applied perpendicularly to a superconducting thin film. Although theoretical boundary conditions on electromagnetic fields are given at an infinite distance from sources, the FEM method applies boundary conditions at the surface of the mesh, and hence has to incorporate in the model a large volume of air outside the superconducting film. This not only represents an approximation with regard to the theoretical boundary conditions, but also increases the number of degrees of freedom and the computation time. The shell-transformation techniques [1] consists in enclosing the near-field FE model in a meshed shell region, and to map this shell region, which is of finite extension, onto the exterior of the FE model, which is of infinite extension. The shell region can have various shapes (e.g., hollow parallelepiped and hollow sphere in 3D), and the boundary condition can then be imposed on the outer surface of the shell with no approximation. We investigate the possibility to reduce the number of degrees of freedom with the help of the shell transformation techniques, in the framework of an H-phi formulation. To this aim, we compare the number of degrees of freedom, the computational time, and the accuracy of the solutions in two cases : (1) with a shell-transformation, and (2) : without shell-transformation, in a large non conducting domain. The obtained results are compared for different geometries (thin disk and thin strip in the critical state, square thin film). The influence of the order of the elements in the transformed region, the shape and size of the region where the shell-transformation is applied, and the mesh quality inside this region are also considered. [less ▲]

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See detailImproved Energy-Based Hysteresis Model and Parameter Identification for Magnetic Hysteresis Materials
Jacques, Kevin ULiege; Henrotte, François ULiege; Geuzaine, Christophe ULiege et al

Conference (2018, April 12)

This paper aims first to clarify the transition between the thermodynamic balance from the mesoscale, at the scale of one cell, to the macroscale, at the homogenized level. Actually this homogenization ... [more ▼]

This paper aims first to clarify the transition between the thermodynamic balance from the mesoscale, at the scale of one cell, to the macroscale, at the homogenized level. Actually this homogenization can be tackled in different ways, leading to different construction of EB hysteresis loops, one approach being in better agreement with experimental data. Then, the observed asymmetry between ascending and descending branches in measured hysteresis loops, which cannot be accounted for by the original EB model, is further investigated. An extension of the EB model is proposed and a comparison with classical Jiles-Atherton results to material measurements will be shown. Additionally, the parameter identification technique will be adapted accordingly in the full paper. [less ▲]

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See detailThree-dimensional modeling of multilayer busbar incorporating domains of lesser dimension
Velasco, Jonathan ULiege; Spirlet, Maxime ULiege; Geuzaine, Christophe ULiege et al

Poster (2018, April 11)

This paper describes the efficient modeling of a three-dimensional busbar, starting from a time-harmonic full-wave finite-element model, modifying the formulation to account for the skin effect, avoiding ... [more ▼]

This paper describes the efficient modeling of a three-dimensional busbar, starting from a time-harmonic full-wave finite-element model, modifying the formulation to account for the skin effect, avoiding the need for explicitly modeling the volumes of the conducting domains. This is performed by specifying jacobian methods on the geometrical transformations based on their dimension (3D, 2D or 1D). [less ▲]

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See detailSteady-State, Nonlinear Analysis of Large Arrays of Electrically Actuated Micromembranes Vibrating in a Fluid
Halbach, Alexandre ULiege; Geuzaine, Christophe ULiege

in Engineering with Computers (2018)

This paper describes a robust and efficient method to obtain the steady-state, nonlinear behaviour of large arrays of electrically actuated micromembranes vibrating in a fluid. The nonlinear ... [more ▼]

This paper describes a robust and efficient method to obtain the steady-state, nonlinear behaviour of large arrays of electrically actuated micromembranes vibrating in a fluid. The nonlinear electromechanical behavior and the multiple vibration harmonics it creates are fully taken into account thanks to a multiharmonic finite element formulation, generated automatically using symbolic calculation. A domain decomposition method allows to consider large arrays of micromembranes by efficiently distributing the computational cost on parallel computers. Two- and three- dimensional examples highlight the main properties of the proposed method. [less ▲]

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See detailMultiscale finite element modeling of nonlinear magnetoquasistatic problems using magnetic induction conforming formulations
Niyonzima, I.; Sabariego, R. V.; Dular, P. et al

in Multiscale Modeling and Simulation (2018), 16(1), 300-326

In this paper we develop magnetic induction conforming multiscale formulations for magnetoquasistatic problems involving periodic materials. The formulations are derived using the periodic homogenization ... [more ▼]

In this paper we develop magnetic induction conforming multiscale formulations for magnetoquasistatic problems involving periodic materials. The formulations are derived using the periodic homogenization theory and applied within a heterogeneous multiscale approach. Therefore the fine-scale problem is replaced by a macroscale problem defined on a coarse mesh that covers the entire domain and many mesoscale problems defined on finely-meshed small areas around some points of interest of the macroscale mesh (e.g., numerical quadrature points). The exchange of information between these macro and meso problems is thoroughly explained in this paper. For the sake of validation, we consider a two-dimensional geometry of an idealized periodic soft magnetic composite. © 2018 Society for Industrial and Applied Mathematics. [less ▲]

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See detailRepresentation of microstructural features and magnetic anisotropy of electrical steels in an energy-based vector hysteresis model
Jacques, Kevin ULiege; Steentjes, Simon; Henrotte, François ULiege et al

in AIP Advances (2018), 8(4),

This paper demonstrates how the statistical distribution of pinning fields in a ferromagnetic material can be identified systematically from standard magnetic measurements, Epstein frame or Single Sheet ... [more ▼]

This paper demonstrates how the statistical distribution of pinning fields in a ferromagnetic material can be identified systematically from standard magnetic measurements, Epstein frame or Single Sheet Tester (SST). The correlation between the pinning field distribution and microstructural parameters of the material is then analyzed. © 2017 Author(s). [less ▲]

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See detailA coupled electro-thermal Discontinuous Galerkin method
Homsi, Lina ULiege; Geuzaine, Christophe ULiege; Noels, Ludovic ULiege

in Journal of Computational Physics (2017), 348

This paper presents a Discontinuous Galerkin scheme in order to solve the nonlinear elliptic partial differential equations of coupled electro-thermal problems. In this paper we discuss the fundamental ... [more ▼]

This paper presents a Discontinuous Galerkin scheme in order to solve the nonlinear elliptic partial differential equations of coupled electro-thermal problems. In this paper we discuss the fundamental equations for the transport of electricity and heat, in terms of macroscopic variables such as temperature and electric potential. A fully coupled nonlinear weak formulation for electro-thermal problems is developed based on continuum mechanics equations expressed in terms of energetically conjugated pair of fluxes and fields gradients. The weak form can thus be formulated as a Discontinuous Galerkin method. The existence and uniqueness of the weak form solution are proved. The numerical properties of the nonlinear elliptic problems i.e., consistency and stability, are demonstrated under specific conditions, i.e. use of high enough stabilization parameter and at least quadratic polynomial approximations. Moreover the prior error estimates in the H1-norm and in the L2-norm are shown to be optimal in the mesh size with the polynomial approximation degree. [less ▲]

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See detailComparison between The Energy-Based Hysteresis Model and The Jiles-Atherton Model in Finite Element Simulations
Jacques, Kevin ULiege; Henrotte, François ULiege; Gyselinck, Johan et al

Conference (2017, September 06)

This paper focuses on ferromagnetic hysteresis phenomena, a crucial point in the evaluation of iron losses in the modelling of electromagnetic devices. The Energy-Based hysteresis model appears as a ... [more ▼]

This paper focuses on ferromagnetic hysteresis phenomena, a crucial point in the evaluation of iron losses in the modelling of electromagnetic devices. The Energy-Based hysteresis model appears as a convenient candidate for the representation of magnetic hysteresis within numerical simulations. Built from thermodynamic principles and inspired by dry-friction like mechanisms in viscoplasticity, this naturally vectorial model offers the possibility to calculate directly the stored and dissipated energy at any time, not only after the closure of minor hysteresis loops. The model parameters are identified from common material measurements and their number is not limited, allowing for a trade-off between accuracy and complexity. In this paper, this model is incorporated into 2D magnetic vector potential finite element formulation simulations and compared with the very popular Jiles-Atherton hysteresis model on the basis of their ability to accurately and efficiently predict measurements from an experimental set-up constituted by a three limbed ferromagnetic core. [less ▲]

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See detailModel Order Reduction of Nonlinear Eddy Current Problems Using Missing Point Estimation
Paquay, Yannick ULiege; Bruls, Olivier ULiege; Geuzaine, Christophe ULiege

in Model Reduction of Parametrized Systems (2017)

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See detailExperimental Correction of Radiation Patterns Between Electromagnetic Environments
Spirlet, Maxime ULiege; Geuzaine, Christophe ULiege; Beauvois, Véronique ULiege

in IEEE Transactions on Antennas and Propagation (2017), 65(03),

This manuscript presents an experimental method to estimate a radiation pattern obtained in a particular echoic environment (for example from in-situ measurements) as if measurements were performed in a ... [more ▼]

This manuscript presents an experimental method to estimate a radiation pattern obtained in a particular echoic environment (for example from in-situ measurements) as if measurements were performed in a given anechoic chamber. The correction is achieved using some reference measurements collected both in echoic and anechoic environments. An angular transfer function is estimated from these two sets of measurements and deconvolved from the measured radiation pattern to be corrected. [less ▲]

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See detailPerfectly matched layers for convex truncated domains with discontinuous Galerkin time domain simulations
Modave, Axel; Lambrechts, Jonathan; Geuzaine, Christophe ULiege

in Computers and Mathematics with Applications (2017), 73(4), 684-700

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See detailShape and Topology Optimization of Electrical Machines using Lie Derivative-Based Analytical Sensitivity Analysis
Kuci, Erin ULiege; Henrotte, François ULiege; Duysinx, Pierre ULiege et al

in 2016 IEEE Conference on Electromagnetic Field Computation (CEFC) (2017)

The paper addresses the optimal design of electric machines, through the general setting of both shape and topology optimization. The optimization problems are efficiently solved with a classical gradient ... [more ▼]

The paper addresses the optimal design of electric machines, through the general setting of both shape and topology optimization. The optimization problems are efficiently solved with a classical gradient-based mathematical programming algorithm. An analytical sensitivity analysis for the nonlinear magnetostatic problem that can handle both shape and topology design variables, based on the Lie derivative is derived and applied to the optimal design of an interior permanent magnet (IPM) machine. [less ▲]

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See detailDesign sensitivity analysis for shape optimization based on the Lie derivative
Kuci, Erin ULiege; Henrotte, François ULiege; Duysinx, Pierre ULiege et al

in Computer Methods in Applied Mechanics and Engineering (2017)

Abstract The paper presents a theoretical framework for the shape sensitivity analysis of systems governed by partial differential equations. The proposed approach, based on geometrical concepts borrowed ... [more ▼]

Abstract The paper presents a theoretical framework for the shape sensitivity analysis of systems governed by partial differential equations. The proposed approach, based on geometrical concepts borrowed from differential geometry, shows that sensitivity of a performance function (i.e. any function of the solution of the problem) with respect to a given design variable can be represented mathematically as a Lie derivative, i.e. the derivative of that performance function along a flow representing the continuous shape modification of the geometrical model induced by the variation of the considered design variable. Theoretical formulae to express sensitivity analytically are demonstrated in detail in the paper, and applied to a nonlinear magnetostatic and a linear elastic problem, following both the direct and the adjoint approaches. Following the analytical approach, one linear system of which only the right-hand side needs be evaluated (the system matrix being known already) has to be solved for each of the design variables in the direct approach, or for each performance functions in the adjoint approach. A substantial gain in computation time is obtained this way compared to a finite difference evaluation of sensitivity, which requires solving a second nonlinear system for each design variable. This is the main motivation of the analytical approach. There is some freedom in the definition of the auxiliary flow that represents the shape modification. We present a method that makes benefit of this freedom to express sensitivity locally as a volume integral over a single layer of finite elements connected to both sides of the surfaces undergoing shape modification. All sensitivity calculations are checked with a finite difference in order to validate the analytic approach. Convergence is analyzed in 2D and 3D, with first and second order finite elements. [less ▲]

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See detailOptimized Schwarz Domain Decomposition Methods for Scalar and Vector Helmholtz Equations
Antoine, Xavier; Geuzaine, Christophe ULiege

in Lahaye, Domenico; Tang, Jok; Vuik, Kees (Eds.) Modern Solvers for Helmholtz Problems (2017)

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See detailWaveform relaxation for the computational homogenization of multiscale magnetoquasistatic problems
Niyonzima, Innocent; Geuzaine, Christophe ULiege; Schöps, Sebastian

in Journal of Computational Physics (2016), 327

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See detailDual Magnetodynamic Finite Element Formulations with Inclusion of an Energy-Based Hysteresis Model
Jacques, Kevin ULiege; Dular, Patrick; Geuzaine, Christophe ULiege et al

Conference (2016, November 16)

This paper studies dual magnetodynamic 2D finite element h - phi and a - v formulations including an energy-based hysteresis model. These formulations use unknowns directly associated with the magnetic ... [more ▼]

This paper studies dual magnetodynamic 2D finite element h - phi and a - v formulations including an energy-based hysteresis model. These formulations use unknowns directly associated with the magnetic field h and the magnetic flux density b respectively. Therefore, the direct form of the hysteresis model (having h as input) is exploited for the h - phi formulation, while the costly and sometimes unstable inverted form (having b as input) is used for the a - v formulation. Both formulations are evaluated in terms of robustness, efficiency and computational cost. As test case, the behaviour of a three-phase transformer is simulated. A good agreement is observed for global and local results obtained with each formulation. [less ▲]

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