Publications

2007

• Convergence analysis of the Jacobi-Davidson method applied to a generalized eigenproblem
  
  • Hechme Grace
  Comptes Rendus. Mathématique, Académie des sciences (Paris), 2007, 345 (5), pp.293-296. In this Note we consider the Jacobi-Davidson method applied to a nonsymmetric generalized eigenproblem. We analyze the convergence behavior of the method when the linear systems involved, known as the correction equations, are solved approximately. Our analysis also exhibits quadratic convergence when the corrections are solved exactly. To cite this article: G. Hechme, C. R. Acad. Sci. Paris, Ser. I 345 (2007). © 2007 Académie des sciences. (10.1016/j.crma.2007.07.003)
  DOI : 10.1016/j.crma.2007.07.003
• Non-Spurious Spectral Like Element Methods for Maxwell's equations
  
  • Cohen Gary
  • Duruflé Marc
  Journal of Computational Mathematics -International Edition-, Global Science Press, 2007, pp.282-304. In this paper, we give the state of the art for the so called "mixed spectral elements" for Maxwell's equations. Several families of elements, such as edge elements and discontinuous Galerkin methods (DGM) are presented and discussed. In particular, we show the need of introducing some numerical dissipation terms to avoid spurious modes in these methods. Such terms are classical for DGM but their use for edge element methods is a novel approach described in this paper. Finally, numerical experiments show the fast and low-cost character of these elements.
• Spectral theory for an elastic thin plate floating on water of finite depth
  
  • Hazard Christophe
  • Meylan Michael H.
  SIAM Journal on Applied Mathematics, Society for Industrial and Applied Mathematics, 2007, 68 (3), pp.629-647. The spectral theory for a two-dimensional elastic plate floating on water of finite depth is developed (this reduces to a floating rigid body or a fixed body under certain limits). Two spectral theories are presented based on the first-order and second-order formulations of the problem. The first-order theory is valid only for a massless plate, while the second-order theory applies for a plate with mass. The spectral theory is based on an inner product (different for the first- and second-order formulations) in which the evolution operator is self-adjoint. This allows the time-dependent solution to be expanded in the eigenfunctions of the self-adjoint operator which are nothing more than the single frequency solutions. We present results which show that the solution is the same as those found previously when the water depth is shallow, and show the effect of increasing the water depth and the plate mass. © 2007 Society for Industrial and Applied Mathematics. (10.1137/060665208)
  DOI : 10.1137/060665208
• Generalized formulations of Maxwell's equations for numerical Vlasov-Maxwell simulations
  
  • Ciarlet Patrick
  • Barthelmé Régine
  • Sonnendrücker Eric
  Mathematical Models and Methods in Applied Sciences, World Scientific Publishing, 2007, 17 (5), pp.657--680. (10.1142/S0218202507002066)
  DOI : 10.1142/S0218202507002066
• Asymptotic analysis for the solution to the Helmholtz problem in the exterior of a finite thin straight wire
  
  • Claeys Xavier
  , 2007. In this document we are interested in the solution of the Helmholtz equation with Dirichlet boundary condition in the exterior of a thin elongated body. We suppose that the geometry is well described in ellipsoidal coordinates. We propose an asymptotic analysis of this problem, using matched expansions. This leads to the construction of an approximate field with more explicit expression. The approximate field is composed of the first terms of the asymptotic expansion of the exact solution. Our study also leads to a validation of an acoustic version of the Pocklington's equation.
• Asymptotic expansion of highly conductive thin sheets
  
  • Schmidt Kersten
  • Tordeux Sébastien
  , 2007, 7 issue 1, pp.2040011-2040012. (10.1002/pamm.200700278)
  DOI : 10.1002/pamm.200700278
• Augmented Galerkin Schemes for the Numerical Solution of Scattering by Small Obstacles.
  
  • Claeys Xavier
  • Collino Francis
  , 2007. Dans le contexte de la propagation des ondes electromagnétiques, nous nous intéressons au problème de diffraction par des fils minces parfaitement conducteurs. Si l'on suppose que leur épaisseur est bien plus petite que la longueur d'onde caractéritique de l'onde incidente, il n'est pas posible de prendre en compte des fils minces sans faire face à un problème de verrouillage numérique. Le modèle de Holland, largement utilisé dans les codes différences finis, fournit une solution pragmatique à ce problème, en modifiant le schéma numérique sur quelques noeuds du maillage avoisinant les fils. Jusqu'à présent ce modèle n'a pas re\c cu de justification théorique solide, et il implique un paramètre appelé l'inductance linéique, qu'il doit être choisi suivant des considértions heuristiques. Nous nous intéressons ici au problème modèle de la diffraction acourtique par un petit obstacle, avec condition de Dirichlet au bord, en deux dimensions dans un milieu homogène. Nous présentons et analysons un schéma numérique qui est compatible avec les méthodes éléments finis standards (sans raffinement de maillage) et ne souffre de verrouillage numérique. Ce schéma mélange des techniques d'analyse asymptotique avec une formulation de type domaine fictif. Suivant les résultats que nous démontrons sur ce schéma, nous aboutissons à une généralisation du modèle de Holland et à un calcul automatique de l'inductance linéique. Notre analyse amène, à notre connaissance, à la première justification théorique de ce type de modèle.
• Continuous Galerkin methods for solving the time-dependent Maxwell equations in 3D geometries
  
  • Ciarlet Patrick
  • Jamelot Erell
  Journal of Computational Physics, Elsevier, 2007, 226 (1), pp.1122-1135. A few years ago, Costabel and Dauge proposed a variational setting, which allows one to solve numerically the time-harmonic Maxwell equations in 3D geometries with the help of a continuous approximation of the electromagnetic field. In this paper, we investigate how their framework can be adapted to compute the solution to the time-dependent Maxwell equations. In addition, we propose some extensions, such as the introduction of a mixed variational setting and its discretization, to handle the constraint on the divergence of the field. © 2007 Elsevier Inc. All rights reserved. (10.1016/j.jcp.2007.05.029)
  DOI : 10.1016/j.jcp.2007.05.029