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Limite quasi-neutre en dimension 1

Emmanuel Grenier — 1999

Journées équations aux dérivées partielles

L’objet de cette note est d’étudier la limite quasineutre des équations de Vlasov Poisson en dimension 1 d’espace. Ceci inclut l’obtention de résultats d’existence pour le système limite ainsi que la preuve de la convergence.

On the derivation of homogeneous hydrostatic equations

Emmanuel Grenier — 2010

ESAIM: Mathematical Modelling and Numerical Analysis

In this paper we study the derivation of homogeneous hydrostatic equations starting from 2D Euler equations, following for instance [2,9]. We give a convergence result for convex profiles and a divergence result for a particular inflexion profile.

Numerical boundary layers for hyperbolic systems in 1-D

Claire Chainais-HillairetEmmanuel Grenier — 2001

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

The aim of this paper is to investigate the stability of boundary layers which appear in numerical solutions of hyperbolic systems of conservation laws in one space dimension on regular meshes. We prove stability under a size condition for Lax Friedrichs type schemes and inconditionnal stability in the scalar case. Examples of unstable boundary layers are also given.

A zoology of boundary layers.

In meteorology and magnetohydrodynamics many different boundary layers appear. Some of them are already mathematically well known, like Ekman or Hartmann layers. Others remain unstudied, and can be much more complex. The aim of this paper is to give a simple and unified presentation of the main boundary layers, and to propose a simple method to derive their sizes and equations.

Numerical boundary layers for hyperbolic systems in 1-D

Claire Chainais-HillairetEmmanuel Grenier — 2010

ESAIM: Mathematical Modelling and Numerical Analysis

The aim of this paper is to investigate the stability of boundary layers which appear in numerical solutions of hyperbolic systems of conservation laws in one space dimension on regular meshes. We prove stability under a size condition for Lax Friedrichs type schemes and inconditionnal stability in the scalar case. Examples of unstable boundary layers are also given.

Ekman boundary layers in rotating fluids

Jean-Yves CheminBenoît DesjardinsIsabelle GallagherEmmanuel Grenier — 2002

ESAIM: Control, Optimisation and Calculus of Variations

In this paper, we investigate the problem of fast rotating fluids between two infinite plates with Dirichlet boundary conditions and “turbulent viscosity” for general L 2 initial data. We use dispersive effect to prove strong convergence to the solution of the bimensionnal Navier-Stokes equations modified by the Ekman pumping term.

On the spectral instability of parallel shear flows

Emmanuel GrenierYan GuoToan T. Nguyen

Séminaire Laurent Schwartz — EDP et applications

This short note is to announce our recent results [2,3] which provide a complete mathematical proof of the viscous destabilization phenomenon, pointed out by Heisenberg (1924), C.C. Lin and Tollmien (1940s), among other prominent physicists. Precisely, we construct growing modes of the linearized Navier-Stokes equations about general stationary shear flows in a bounded channel (channel flows) or on a half-space (boundary layers), for sufficiently large Reynolds number R . Such an instability is linked...

Oscillatory limits with varying spectrum

Emmanuel Grenier — 2012

ESAIM: Proceedings

High time frequency oscillations occur in many different physical cases: slightly compressible fluids, almost quasineutral plasmas, small electron mass approximation .... In many case, small parameters arise in fluids mechanics or plasma physics, leading to these oscillations as the small parameter goes to zero. The aim of this note is to detail how to obtain formal expansions and to give some indications on how to justify them.

Ekman boundary layers in rotating fluids

Jean-Yves CheminBenoît DesjardinsIsabelle GallagherEmmanuel Grenier — 2010

ESAIM: Control, Optimisation and Calculus of Variations

In this paper, we investigate the problem of fast rotating fluids between two infinite plates with Dirichlet boundary conditions and “turbulent viscosity” for general initial data. We use dispersive effect to prove strong convergence to the solution of the bimensionnal Navier-Stokes equations modified by the Ekman pumping term.

Fluids with anisotropic viscosity

Jean-Yves CheminBenoît DesjardinsIsabelle GallagherEmmanuel Grenier — 2010

ESAIM: Mathematical Modelling and Numerical Analysis

Motivated by rotating fluids, we study incompressible fluids with anisotropic viscosity. We use anisotropic spaces that enable us to prove existence theorems for less regular initial data than usual. In the case of rotating fluids, in the whole space, we prove Strichartz-type anisotropic, dispersive estimates which allow us to prove global wellposedness for fast enough rotation.

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