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See detailA non-destructive testing application solved with A-X geometric eddy-current formulation
Codecasa, Lorenzo; Dular, Patrick ULg; Specogna, Ruben et al

in COMPEL (2010), 29(6), 1606-1615

Purpose – The purpose of this paper is to introduce a perturbation method for the A-X geometric formulation to solve eddy-current problems and apply it to the feasibility design of a non-destructive ... [more ▼]

Purpose – The purpose of this paper is to introduce a perturbation method for the A-X geometric formulation to solve eddy-current problems and apply it to the feasibility design of a non-destructive evaluation device suitable to detect long-longitudinal volumetric flaws in hot steel bars. Design/methodology/approach – The effect of the flaw is accurately and efficiently computed by solving an eddy-current problem over an hexahedral grid which gives directly the perturbation due to the flaw with respect to the unperturbed configuration. Findings – The perturbation method, reducing the cancelation error, produces accurate results also for small variations between the solutions obtained in the perturbed and unperturbed configurations. This is especially required when the tool is used as a forward solver for an inverse problem. The method yields also to a considerable speedup: the mesh used in the perturbed problem can in fact be reduced at a small fraction of the initial mesh, considering only a limited region surrounding the flaw in which the mesh can be refined. Moreover, the full three-dimensional unperturbed problem does not need to be solved, since the source term for computing the perturbation is evaluated by solving a two-dimensional flawless configuration having revolution symmetry. Originality/value – A perturbation method for the A-X geometric formulation to solve eddy-current problems has been introduced. The advantages of the perturbation method for non-destructive testing applications have been described. [less ▲]

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See detailFinite-Element Analysis of a Shielded Pulsed-Current Induction Heater -- Experimental Validation of a Time-Domain Thin-Shell Approach
V Sabariego, Ruth ULg; Sergeant, Peter; Gyselinck, Johan et al

in COMPEL (2010), 29(6), 1585-1595

Purpose – The aim of this paper is the experimental validation of an original time-domain thin-shell formulation. The numerical results of a three-dimensional thin-shell model are compared with the ... [more ▼]

Purpose – The aim of this paper is the experimental validation of an original time-domain thin-shell formulation. The numerical results of a three-dimensional thin-shell model are compared with the measurements performed on a heating device at different working frequencies. Design/methodology/approach – A time-domain extension of the classical frequency-domain thin-shell approach is used for the finite-element analysis of a shielded pulse-current induction heater. The time-domain interface conditions at the shell surface are expressed in terms of the average flux density vector in the shell, as well as in terms of a limited number of higher-order components. Findings – A very good agreement between measurements and simulations is observed. A clear advantage of the proposed thin-shell approach is that the mesh of the computation domain does not depend on the working frequency anymore. It provides a good compromise between computational cost and accuracy. Indeed, adding a sufficient number of induction components, a very high accuracy can be achieved. Originality/value – The method is based on the coupling of a time-domain 1D thin-shell model with a magnetic vector potential formulation via the surface integral term. A limited number of additional unknowns for the magnetic flux density are incorporated on the shell boundary. [less ▲]

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See detailMagnetic model refinement via a perturbation finite element method – from 1D to 3D
Dular, Patrick ULg; V Sabariego, Ruth ULg; Krähenbühl, Laurent

in COMPEL (2009), 28(4), 974-988

Purpose – The purpose of this paper is to develop a sub-domain perturbation technique for refining magnetic circuit models with finite element (FE) models of different dimensions. Design/methodology ... [more ▼]

Purpose – The purpose of this paper is to develop a sub-domain perturbation technique for refining magnetic circuit models with finite element (FE) models of different dimensions. Design/methodology/approach – A simplified problem considering ideal flux tubes is first solved, as either a 1D magnetic circuit or a simplified FE problem. Its solution is then corrected via FE perturbation problems considering the actual flux tube geometry and the exterior regions, that allow first 2D and then 3D leakage fluxes. Each of these sub-problems requires an appropriate proper volume mesh, with no need of interconnection. The solutions are transferred from one problem to the other through projections of source fields between meshes. Findings – The developed perturbation FE method allows to split magnetic circuit analyses into subproblems of lower complexity with regard to meshing operations and computational aspects. A natural progression from simple to more elaborate models, from 1D to 3D geometries, is thus possible, while quantifying the gain given by each model refinement and justifying its utility. Originality/value – Approximate problems with ideal flux tubes are accurately corrected when accounting for leakage fluxes via surface sources of perturbations. The constraints involved in the subproblems are carefully defined in the resulting FE formulations, respecting their inherent strong and weak nature. As a result, an efficient and accurate computation of local fields and global quantities, i.e. flux, MMF, reluctance, is obtained. The method is naturally adapted to parameterized analyses on geometrical and material data. [less ▲]

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See detailh- and b-conform finite element perturbation techniques for nondestructive eddy current testing
V Sabariego, Ruth ULg; Dular, Patrick ULg

in COMPEL (2008), 27(1), 319-327

Purpose - The aim of the present paper is to compare the performances of a finite-element perturbation technique applied either to the h- conform magnetodynamic formulation or to its b-conform counterpart ... [more ▼]

Purpose - The aim of the present paper is to compare the performances of a finite-element perturbation technique applied either to the h- conform magnetodynamic formulation or to its b-conform counterpart in the frame of nondestructive eddy-current testing problems. Design/methodology/approach - In both complementary perturbation techniques, the computation is split into a computation without defect (unperturbed problem) and a computation of the field distorsion due to its presence (perturbation problem). The unperturbed problem is conventionally solved in the complete domain. The source of the perturbation problem is then determined by the projection of the unperturbed solution in a relatively small region surrounding the defect. The discretisation of this reduced domain is chosen independently of the dimensions of the excitation probe and the specimen under study and is thus well adapted to the size of the defect. Findings - The accuracy of the perturbation model is evidenced by comparing the results of the two counterpart formulations to those achieved in the conventional way for different dimensions of the reduced domain. The size of the reduced domain increases with the size of the defect at hand. This proposed sub-domain approach eases considerably the meshing process and speeds-up the computation for different probe positions. Originality/value - At a discrete level, the impedance change due to the defect is efficiently and accurately computed by integrating only over the defect itself and a layer of elements in the reduced domain that touches its boundary. Therefore, no integration of any flux variation in the coils is required. [less ▲]

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See detailSubdomain Perturbation Finite Element Method for Skin and Proximity Effects in Inductors
Dular, Patrick ULg; V Sabariego, Ruth ULg; Krähenbühl, Laurent

in COMPEL (2008), 27(4), 72-84

Purpose – This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE ... [more ▼]

Purpose – This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE) analyses. Design/methodology/approach – A reference eddy current FE problem is first solved by considering perfect conductors. This is done via appropriate boundary conditions (BCs) on the conductors. Next the solution of the reference problem gives the source for eddy current FE perturbation sub-problems in each conductor then considered with a finite conductivity. Each of these problems requires an appropriate volume mesh of the associated conductor and its surrounding region. Findings – The skin and proximity effects in both active and passive conductors can be accurately determined in a wide frequency range, allowing for precise losses calculations in inductors as well as in external conducting pieces. Originality/value – The developed method allows one to accurately determine the current density distributions and ensuing losses in conductors of any shape, not only in the frequency domain but also in the time domain. Therefore, it extends the domain of validity and applicability of impedance-type BC techniques. It also offers an original way to uncouple FE regions that allows the solution process to be lightened, as well as efficient parameterized analyses on the signal form and the conductor characteristics. [less ▲]

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See detailA finite element analysis of spatial solitons in optical fibres
Nicolet, A.; Drouart, F.; Renversez, G. et al

in COMPEL (2007), 26(4), 1105--1113

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See detailA perturbation finite element method for modeling moving conductive and magnetic regions without remeshing
Dular, Patrick ULg; V Sabariego, Ruth ULg

in COMPEL (2007), 26(3), 700-711

Purpose - To develop a sub-domain perturbation technique for efficiently modeling moving systems in magnetodynamics with a magnetic field h-conform finite element (FE) formulation. Design/methodology ... [more ▼]

Purpose - To develop a sub-domain perturbation technique for efficiently modeling moving systems in magnetodynamics with a magnetic field h-conform finite element (FE) formulation. Design/methodology/approach - A reference problem is first solved in a global mesh excluding some moving regions and thus avoiding the inclusion of their meshes. Its solution gives the sources for a sequence of perturbation problems with the supplementary moving magnetic and conductive regions. Each of these sub-problems requires an appropriate proper volume mesh of the associated moving region and its surrounding region, with no need of interconnection. The solutions are transferred from one problem to the other through projections of source fields between meshes. Findings - The consideration of sub-problems and associated sources, in a sequence of perturbation problems, leads to a significant speed-up of the repetitive solutions in analyses of moving systems. A free movement in any direction can be considered with no need of remeshing. Originality/value - When working with the perturbation fields, the volume sources can be limited to the moving regions, what allows for homogeneous perturbation boundary conditions and reduces the computational efforts for projecting and evaluating the sources. The curl-conformity of the unknown magnetic field is preserved during the whole process thanks to the use of edge FEs for both the magnetic field and the intermediate source quantities. The sub-problem approach also gives an easy way to directly express the time derivatives in moving frames. [less ▲]

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See detailSub-domain finite element method for efficiently considering strong skin and proximity effects
Dular, Patrick ULg; V Sabariego, Ruth ULg; Gyselinck, Johan et al

in COMPEL (2007), 26(4), 974-985

Purpose - This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE ... [more ▼]

Purpose - This paper seeks to develop a sub-domain perturbation technique to efficiently calculate strong skin and proximity effects in conductors within frequency and time domain finite element (FE) analyses. Design/methodology/approach - A reference eddy current FE problem is first solved by considering perfect conductors. This is done via appropriate boundary conditions (BCs) on the conductors. Next the solution of the reference problem gives the source for eddy current FE perturbation sub-problems in each conductor then considered with a finite conductivity. Each of these problems requires an appropriate volume mesh of the associated conductor and its surrounding region. Findings - The skin and proximity effects in both active and passive conductors can be accurately determined in a wide frequency range, allowing for precise losses calculations in inductors as well as in external conducting pieces. Originality/value - The developed method allows one to accurately determine the current density distributions and ensuing losses in conductors of any shape, not only in the frequency domain but also in the time domain. Therefore, it extends the domain of validity and applicability of impedance-type BC techniques. It also offers an original way to uncouple FE regions that allows the solution process to be lightened, as well as efficient parameterized analyses on the signal form and the conductor characteristics. [less ▲]

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See detailAccuracy analysis of the thrust force in 2D-3D finite element models
Deliège, Geoffrey ULg; Henrotte, François; Hameyer, Kay

in COMPEL (2006), 25(2), 320-333

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See detailThree-dimensional finite element modeling of inductive and capacitive effects in micro-coils
Dular, Patrick ULg; V Sabariego, Ruth ULg; Kuo-Peng, Patrick

in COMPEL (2006), 25(3), 642-651

Purpose - The paper seeks to develop dual 3D finite element (FE) formulations for modeling both inductive and capacitive effects in massive inductors, in particular micro-coils. The paper aims to build ... [more ▼]

Purpose - The paper seeks to develop dual 3D finite element (FE) formulations for modeling both inductive and capacitive effects in massive inductors, in particular micro-coils. The paper aims to build circuit relations relating the voltages and the currents in such inductors to be used in circuit coupling. Design/methodology/approach - A circuit relation involving a unique voltage and complementary inductive and capacitive currents is defined for each inductor. the inductive circuit relation is first classically obtained by a FE magnetodynamic model. Then, the capacitive relation is obtained through a FE electric model, using sources evaluated from the first model. The conformity is defined on one hand for the magnetic flux density and the electric field, and on the other hand for the magnetic field and the electric flux density. Mixed FE, i.e. nodal, edge and face elements, are used to satisfy each chosen conformity level for the unknown fields and to naturally define the involved global quantities, i.e. the voltages, currents and charges. Findings - This contribution points out the interest of satisfying conformity properties for the coupled magnetic and electric problems. An accurate computation of these effects is obtained in the critical frequency range of their strong interaction. In addition, the complementarity of dual solutions gives the possibility to estimate the discretisation error. Originality/value - The mathematical and discretisation tools for any wished conformity level are unified for naturally coupling magnetic and electric problems. The global quantities basis functions involved in the FE circuit relations benefit from a significant support reduction, which facilitates their evaluation and gives them direct physical interpretations. [less ▲]

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See detail2D Harmonic Balance FE Modelling of Electromagnetic Devices coupled to Nonlinear Circuits
Gyselinck, J.; Dular, Patrick ULg; Geuzaine, Christophe ULg et al

in COMPEL (2004), 23(3), 800--812

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See detailApplication of data mining to optimize settings for generator tripping and load shedding system in emergency control at Hydro-Quebec
Huang, J. A.; Harrison, S.; Vanier, G. et al

in COMPEL (2004), 23(1 Sp. Iss. SI), 21-34

This paper describes the on-going work done by Hydro-Quebec to optimize the settings of automatic devices installed in its main power plants to maintain secure operation under extreme contingencies. The ... [more ▼]

This paper describes the on-going work done by Hydro-Quebec to optimize the settings of automatic devices installed in its main power plants to maintain secure operation under extreme contingencies. The automatic generator tripping and load shedding system (RPTC) described in this paper is installed at the Churchill Falls hydroelectric power plant (5,500 MW) in Labrador. Data mining techniques such as decision trees and regression trees have been used. Real time snapshots of the Hydro-Quebec power system collected over a 5 year period have been used to generate large amounts of results by transient stability simulations. The processing of these data has been done using software developed by the University of Liege. This approach gives the most relevant parameters and finds optimal settings for the RPTC system, minimizing the number of tripped generator units while maintaining the same performance in terms of security coverage. New operation rules can thus be established. [less ▲]

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See detailComparisons of finite element and Rayleigh methods for the study of conical Bloch waves in arrays of metallic cylinders
Guenneau, S.; Nicolet, A.; Geuzaine, Christophe ULg et al

in COMPEL (2004), 23(4), 932--949

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See detailThe eggshell approach for the computation of electromagnetic forces in 2D and 3D
Henrotte, François; Deliège, Geoffrey ULg; Hameyer, Kay

in COMPEL (2004), 23(4), 996-1005

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See detailCoupled mechanical-electrostatic FE-BE analysis with FMM acceleration
V Sabariego, Ruth ULg; Gyselinck, Johan; Dular, Patrick ULg et al

in COMPEL (2004), 23(4), 876-884

This paper deals with the coupled mechanical-electrostatic analysis of a shunt capacitive MEMS switch. The mechanical and electrostatic parts of the problem are modelled by the FE and BE methods ... [more ▼]

This paper deals with the coupled mechanical-electrostatic analysis of a shunt capacitive MEMS switch. The mechanical and electrostatic parts of the problem are modelled by the FE and BE methods, respectively. The fast multipole method is applied to reduce the storage requirements and the computational cost of the BE electrostatic model An adaptive truncation expansion of the 3D Laplace Green function is employed The strong interaction between the mechanical and electrostatic systems is considered iteratively. [less ▲]

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See detail3D h-phi finite element formulation for the computation of a linear transverse flux actuator
Deliège, Geoffrey ULg; Henrotte, François; Vande Sande, Hans et al

in COMPEL (2003), 22(4), 1077-1088

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See detailApplication of the fast multipole method to the 2D finite element-boundary element analysis of electromechanical devices
V Sabariego, Ruth ULg; Gyselinck, J.; Geuzaine, Christophe ULg et al

in COMPEL (2003), 22(3), 659-673

The present paper deals with the fast multipole acceleration of the 2D finite element-boundary element modelling of electromechanical devices. It is shown that the fast multipole method, usually applied ... [more ▼]

The present paper deals with the fast multipole acceleration of the 2D finite element-boundary element modelling of electromechanical devices. It is shown that the fast multipole method, usually applied to large 3D problems, can also lead to a reduction in computational time when dealing with relatively small 2D problems, provided that an adaptive truncation scheme for the expansion of the 2D Laplace Green function is used. As an application example, the 2D hybrid modelling of a linear actuator is studied, taking into account saturation, the voltage supply and the mechanical equation. The computational cost without and with fast multipole acceleration is discussed for both the Linear and nonlinear case. [less ▲]

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See detailA finite element formulation for spectral problems in optical fibers
Guenneau, S.; Nicolet, A.; Zolla, F. et al

in COMPEL (2001), 20(1), 120--131

Detailed reference viewed: 7 (2 ULg)