Dorsey, Di Bartolo and Dolgert (Di Bartolo et al., 1996; 1997) have constructed asymptotic matched solutions at order two for the half-space Ginzburg-Landau model, in the weak-κ limit. These authors deduceda formal expansion for the superheating field in powers of $\kappa^{\frac{1}{2}}$ up to order four, extending the formula by De Gennes (De Gennes, 1966) and the two terms in Parr's formula (Parr, 1976). In this paper, we construct asymptotic matched solutions at all orders leading to a complete expansion in powers of $\kappa^{\frac{1}{2}}$ for the superheating field.

Domain decomposition techniques provide a powerful tool for the numerical approximation of partial differential equations.We focus on mortar finite element methods on non-matching triangulations.In particular, we discuss and analyze dual Lagrange multiplier spacesfor lowest order finite elements.These non standard Lagrange multiplier spaces yield optimal discretizationschemes and a locally supported basis for the associatedconstrained mortar spaces. As a consequence,standard efficient iterative solvers as multigrid methods or domain decomposition techniques can be easily adapted to the nonconformingsituation.Here, we introduce new dual Lagrange multiplier spaces. We concentrateon the construction of locally supported and continuous dualbasis functions.The optimality of the associated mortar method is shown. Numerical results illustrate the performance of our approach.

This work is concerned with the flow of a viscousplastic fluid. We choose a model of Bingham typetaking into account inhomogeneous yield limit of thefluid, which is well-adapted in the description oflandslides. After setting the generalthreedimensional problem, the blocking property isintroduced. We then focus on necessary andsufficient conditions such that blocking of the fluidoccurs.The anti-plane flow intwodimensional andonedimensional cases is considered.A variational formulation in terms of stresses isdeduced. More fine properties dealing with localstagnant regions as well as local regions where thefluid behaves like a rigid body are obtained indimension one.

Les méthodes sans maillage emploient une interpolation associée à un ensemble de particules : aucune information concernant la connectivité ne doit être fournie.Un des atouts de ces méthodes est que la discrétisationpeut être enrichie d'une façon très simple, soit en augmentant le nombre de particules (analogue à lastratégie de raffinement h), soit en augmentant l'ordre de consistance (analogueà la stratégie de raffinement p). Néanmoins, le coût du calcul des fonctionsd'interpolation est très élevé et ceci représente un inconvénient vis-à-visdes éléments finis. Cet article présente une interpolation mixte élémentsfinis-particules qui résulte de la généralisation de plusieurs travaux dans cedomaine. La formulation de cette interpolation mixte est valable pour n'importe quel ordre de consistance. Dans ce contexte, onénonce un estimateur d'erreur a priori dont la démonstrationse base dans les propriétés de l'interpolation mixte.Ce résultat permet d'étudier la convergence de laméthode d'enrichissement et d'établir les stratégies de raffinement del'interpolation qui permettent d'atteindre une solutionavec une précision satisfaisante.

This paper is concerned with the computation of 3D vertex singularities of anisotropic elastic fields with Dirichlet boundary conditions, focusing on the derivation of error estimates for a finite element method on graded meshes. The singularities are described by eigenpairs of a corresponding operator pencil on spherical polygonal domains. The main idea is to introduce a modified quadratic variational boundary eigenvalue problem which consists of two self-adjoint, positive definite sesquilinear forms and a skew-Hermitean form. This eigenvalue problem is discretized by a finite element method on graded meshes. Based on regularity results for the eigensolutions estimates for the finite element error are derived both for the eigenvalues and the eigensolutions. Finally, some numerical results are presented.

In this paper, we prove the convergence of the current defined from the Schrödinger-Poisson system with the presence of a strong magnetic field toward a dissipative solution of the Euler equations.

We analyze the compressible isentropic Navier–Stokes equations (Lions, 1998) in the two-dimensional case with $\gamma=\displaystyle{{c_{p}}/{c_{v}}}=2$ . These equations also modelizethe shallow water problem in height-flow rate formulation used tosolve the flow in lakes and perfectly well-mixed sea. We establisha convergence result for the time-discretized problem when themomentum equation and the continuity equation are solved with theGalerkin method, without adding a penalization term in thecontinuity equation as it is made in Lions (1998). The secondpart is devoted to the numerical analysis and mainly deals withproblems of geophysical fluids. We compare the simulationsobtained with this compressible isentropic Navier–Stokes model andthose obtained with a shallow water model (Di Martino et al., 1999). At first,the computations are executed on a simplified domain in order tovalidate the method by comparison with existing numerical resultsand then on a real domain: the dam of Calacuccia (France). At last, we numerically implement an analyticalexample presented by Weigant (1995) which shows thateven if the data are rather smooth, we cannot have bounds onρ in Lp for p large if $\gamma<2$ when N=2.

We present here a discretization of a nonlinear obliquederivative boundary value problem for the heat equation in dimensiontwo. This finite difference scheme takes advantages of thestructure of the boundary condition, which can be reinterpreted as aBurgers equation in the space variables. This enables to obtain anenergy estimate and to prove the convergence of the scheme. We also provide some numerical simulations of thisproblem and a numerical study of the stability of the scheme, whichappears to be in good agreement with the theory.

The present paper is devoted to the computation of single phase or two phase flows using the single-fluid approach. Governing equations rely on Euler equations which may be supplemented by conservation laws for mass species. Emphasis is given on numerical modelling with help of Godunov scheme or an approximate form of Godunov scheme called VFRoe-ncv based on velocity and pressure variables. Three distinct classes of closure laws to express the internal energy in terms of pressure, density and additional variables are exhibited. It is shown first that a standard conservative formulation of above mentioned schemes enables to predict “perfectly” unsteady contact discontinuities on coarse meshes, when the equation of state (EOS) belongs to the first class. On the basis of previous work issuing from literature, an almost conservative though modified version of the scheme is proposed to deal with EOS in the second or third class. Numerical evidence shows that the accuracy of approximations of discontinuous solutions of standard Riemann problems is strengthened on coarse meshes, but that convergence towards the right shock solution may be lost in some cases involving complex EOS in the third class. Hence, a blend scheme is eventually proposed to benefit from both properties (“perfect” representation of contact discontinuities on coarse meshes, and correct convergence on finer meshes). Computational results based on an approximate Godunov scheme are provided and discussed.

The Boltzmann–Poisson system modeling the electron flow in semiconductorsis used to discuss the validity of the Child–Langmuir asymptotics.The scattering kernel is approximated by a simple relaxation time operator.The Child–Langmuir limit gives an approximation of the current-voltagecharacteristic curves by means of a scalingprocedure in which the ballistic velocity is much larger that the thermal one. We discuss the validity of the Child–Langmuir regime by performing detailed numerical comparisons between the simulation of theBoltzmann–Poisson system and the Child–Langmuir equations in testproblems.

Along with the classical requirements on B-splines bases(minimal support, positivity, normalization)we show that it is natural to introduce an additional“end point property". When dealing with multiple knots,this additional property is exactly the appropriate requirementto obtain the poles of nondegenerate splinesas intersections of osculating flats at consecutive knots.