Influence de l’anisotropie hydrodynamique sur les ecoulements convectifs dans les lits poreux fluidises

In this paper, a study is made of convection heat transfer through packed porous beds which consists of a fluid zone (river) and a porous zone underlined by a surface heated by a constant temperature T1. Thefree surface of the fluid zone, receiving solar rays to length of day, is then supposed heated isothermally at T2 (T2 > T1). The influence of hydrodynamic anisotropy on the convective phenomenon is investigated. It showed that the anisotropic permeability ratio, the inclination angle of the principal axes of the porous medium and the thickness of the porous lining have a strong influence of the geothermal convective flow and help to predict the environmental aquatic behavior. On étudie ici la convection thermique dans les lits poreux fluidisés, constitués d'une zone fluide (cours d'eau) dont la surface libre est à une température constante T2 et reçoit à longueur de journée les rayonssolaires puis d'une zone poreuse limitée en bas par une surface de température T1 (< T2). L'influence de l'anisotropie hydrodynamique sur ce phénomène convectif est examinée. Il ressort que le rapportd'anisotropie en perméabilité, l'angle d'orientation des axes principaux du milieu poreux et l'épaisseur des couches constituant le lit fluidisé, influencent grandement l'écoulement convectif géothermique etaident à prédire le comportement environnemental des milieux aquatiques

On convergence rate of the augmented Lagrangian algorithm for nonsymmetric saddle point problems

Abstract We are interested in solving the system by a variant of the augmented Lagrangian algorithm. This type of problem with nonsymmetric A typically arises in certain discretizations of the Navier-Stokes equations. Here A is a (n, n) matrix, c, F ∈ R n , L is a (m, n) matrix, and λ, G ∈ R m . We assume that A is invertible on the kernel of L. Convergence rates of the augmented Lagrangian algorithm are known in the symmetric case but the proofs in [R. Glowinski, P. LeTallec, Augmented Lagrangian and Operator Splitting Methods in Nonlinear Mechanics, SIAM, 1989] used spectral arguments and cannot be extended to the nonsymmetric case. The purpose of this paper is to give a rate of convergence of a variant of the algorithm in the nonsymmetric case. We illustrate the performance of this algorithm with numerical simulations of the lid-driven cavity flow problem for the 2D Navier-Stokes equations

Distributed approach for aerodynamic model identification of the ice aircraft using the alternating direction method of multipliers in combination with simplotope b-splines

High performance control allocation methods for the Innovative Control Effectors (ICE) aircraft require accurate onboard aerodynamic models, with preferably first order continuity. Simplotope B-Splines, an extension on Simplex B-Splines, have a high approximation power by using local cost functions. However, enforcing global continuity produces computationally expensive optimization problems. This paper presents a distributed approach, using the Alternating DirectionMethod of Multipliers (ADMM), to reduce the complexity of the B-Coefficients’ estimation. ADMM decouples the simplotopes, and introduces coupling coefficients to enforce global continuity, resulting in a parallel estimation algorithm whose complexity is depending solely on the partition size, being independent of refinement of the model tessellation. Results show that for a 3D model, the distributed algorithm converges steadily to the global solution with a good approximation after a couple hundred iterations. Validation results of the distributed approach were similar to those of the global optimal solution for various noise intensities, and the continuity constraints were satisfied with maximum mismatches below 10-4. The distributed approach has been used to construct a first order continuous aerodynamic model for the ICE aircraft, which has been implemented in Simulink, and proven to perform well compared to the original model.Control & SimulationAstrodynamics & Space Mission