Use of direct and large eddy simulations for the development of multicomponent reacting compressible turbulent boundary layer wall model

A study of multicomponent reacting channel flows with significant heat transfer and low Mach number has been performed using a set of direct and large eddy simulations. The use of LES computations was needed to analyze accurate and relevant data of such flows at a sufficient Reynolds number and reasonable computational cost. The analysis of these data will be detailed leading to the development of an analytical wall model for predicting the total shear stress and heat flux at the wall

High Performance Pre-Computing: Prototype Application to a Coastal Flooding Decision Tool

International audienceAfter defining the High Performance Pre- Computing --referred as HPPC-- concept, the aim of the present study is to develop a prototype whether to approve or not the benefits of this concept. Our application case tries to answer the geophysical issue of coastal flooding. This is an example of an alert system based on the HPPC architecture, thus on pre-computed scenarios. The prototype provides the scientists with an ergonomic and on-demand tool allowing the run of scenarios of any implemented numerical models. These runs are available through a web application which submits the corresponding jobs on the remote french public cluster of HPC@LR. In this study we simulate the waves propagation over a Mediterranean grid using the wave model WaveWatch III⃝R . A reference simulation using usual conditions is approximated using the k-NN algorithm over 12, 98 and then 980 pre-computed scenarios. This simple experiment demonstrates how useful the pre-computing of scenarios is for alert systems as far as enough and relevant scenarios are pre-computed. This is the reason why searches continue in each critical points of the HPPC architecture such as the design of experiment, the approximation of the results by meta-models and the research of the closest scenarios in this big data context

A Finite Element Inverse Method for the Design of Turbomachinery Blades

ABSTRACT We present a quasi-3D inverse method for the design of turbomachinery blades corresponding to a velocity distribution give

A PIV-Guided Large-Eddy Simulation of In-Cylinder Flows

A combination of Large-Eddy Simulation (LES) and Particle Image Velocimetry (PIV) was utilized to investigate the three-dimensional in-cylinder flow within an optically accessible Direct Injection Spark Ignition (DISI) engine at motored engine operation. The PIV measurements were used to guide the meshing procedure by identifying the regions were refinements and improvements were needed. From the iteratively optimized meshes LES results are shown from two selected meshes, an intermediate coarse mesh and the final optimized mesh, and compared to PIV measurements. The evolution of the intake flow and the tumble in the central tumble plane during compression are presented and discussed. Exploitation of the LES results allowed showing the influence of out-of-plane velocities along the cylinder liner impacting the formation of the tumble flow. The optimized mesh was then used to investigate the influence of the spark plug on the in-cylinder flow. For the studied engine the spark plug had a significant impact on the evolution of the tumble flow during compression. Finally 35 engine cycles were simulated using the optimized mesh with the spark plug in place. Velocity distributions in a region below the spark plug are shown and compared with PIV results. The two-sample Kolmogorov-Smirnov test revealed a strong similarity between the velocity distributions obtained by PIV and LES, thus validating the potential of LES for investigating cycle-to-cycle variability

Le logiciel libre dans la gestion de projet IT

L’objectif de ce travail de diplôme est d’explorer le monde du logiciel libre, de tester des logiciels libres de gestion de projet et d’avoir l’avis d’entreprises ayant fait la démarche d’utiliser des logiciels libres. Ce mémoire permettra à tous les chefs de projet, qui recherchent un logiciel libre de gestion de projet, d’avoir une description et une étude détaillée de sept logiciels libres de gestion de projet. Ils choisiront le logiciel qui sied le mieux à leurs besoins. De plus, l’analyse facilite au maximum l’utilisation du logiciel choisi. Vous trouverez aussi le compte rendu des entreprises cibles : Hortis, le CTI et LynuxSolutions qui m’ont permis de les interviewer. Les thèmes concernant l’historique, le business et les logiciels libres de l’entreprise, ainsi que la mise en place, l’attente et la sécurité des logiciels libres seront abordés. Il est essentiel que le lecteur utilise cet ouvrage s’il désire se familiariser avec un des sept logiciels libres de gestion de projet qui a passé le test de l’analyse multicritère* avec pondération par matrice de préférence*

Modélisation des flux pariétaux sur les tuyères des moteurs à propergol solide

Les tuyères des moteurs à propergol solide sont soumises à des flux pariétaux intenses. Les composites carbone/carbone sont alors retenus pour assurer l'intégrité des composants. Outre leurs excellentes propriétés thermo-mécaniques, ces matériaux sont exposés au phénomène d'ablation : réaction chimique hétérogène de surface entre le matériau et les espèces oxydantes de l'écoulement. D'une certaine façon, cette spécificité protège la structure car elle permet de réduire considérablement le flux de chaleur entrant dans le solide. En contrepartie, le phénomène doit être parfaitement contrôlé car il s'accompagne d'une récession de la surface. La prédiction des flux pariétaux de masse, de quantité de mouvement, et de chaleur, est donc un point crucial pour la conception des tuyères. La simulation numérique fait maintenant partie des outils de conception incontournables pour la mise au point de nouvelles tuyères. Néanmoins, au vu de la puissance des calculateurs disponibles, l'emploi de modèles de paroi est une étape nécessaire pour pouvoir simuler ces écoulements à l'échelle 1. Dans ce cadre, on présente une série de simulations numériques directes dont l'analyse permet d'élaborer des nouvelles lois de paroi intégrant plusieurs phénomènes physiques complexes qui modifient le comportement "classique" de la couche limite turbulente : dilatabilité de l'écoulement, influence de l'aspect multi-espèces réactif du fluide, nombre de Prandtl non unité, transfert radiatif, gradient de pression longitudinal, et ablation des parois. La mise en oeuvre de ces modèles est dès à présent envisageable.The nozzles of solid rocket motors must resist to severe wall fluxes. Carbon/carbon composite materials are then chosen to insure the structure integrity. In spite of their excellent thermo-mechanical properties, these materials are exposed to the ablation phenomenon: chemical oxidation of the solid material by the combustion products. On the one hand, this feature protects the nozzle structure since this process considerably reduces the wall heat flux. On the other hand, the ablation process must be perfectly controlled because of the geometrical changes induced by the surface recession. The assessment of mass/momentum/heat fluxes at the wall is thus a crucial part for the nozzle design. Numerical simulations are nowadays commonly used to define new nozzles. However, considering the power of the available computers, the use of wall models is a necessary step to simulate full scale devices. With this framework, one presents a set of direct numerical simulations whose analysis allows to derive new wall functions integrating several complex physical aspects that modify the "classical" behavior of the turbulent boundary layer: multicomponent reacting compressible flow, with non-unity Prandtl number, radiative transfer, streamwise pressure gradient, and wall ablation. These new models are now ready to be tested on realistic configurations.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

The Ba 10 S(VO 3 S) 6 Oxysulfide: 1D-Structure and Mixed Anion Chemical Bonding

International audienceThe new oxysulfide Ba10V6S7O18, that can be written as Ba10S(VO3S)6, was prepared by solid state reaction. It crystallizes in the non-centrosymmetric P63 space group with the unit cell parameters a=18.3018(2) Å and c=8.6525(2) Å, R1 = 3.21%. This original phase exhibits (VO3S) units separated by Ba 2+ cations, the later delimit 1D-hexagonal-like cavities filled by disordered sulfur S 2anions and arranged into two kinds of sulfur-deficient 1D-channels. DFT calculations were employed to get insights into the chemical bonding and parameters ruling the structure, particularly the V-O vs. V-S bonding inside the mixed anion VO3S tetrahedra, and the contribution of the S 2of the cavities. The title compound can be decomposed with three components mainly interacting by ionic bonds as follows, Ba10V6S7O18 → [Ba10] 20+ [S] 2-[(VO3S)6] 18-, this description may pave the way to the design of other phases related to this system with adjusted band gap features. In particular, the effect of the V(O,S)4/Ba ratio is discussed to emphasize the presence of the [S] 2component, in comparison with related structures such as Ba6V4O5S11 [Ba6(VO2S2)2(VS3O)(VS4)], as it contributes strongly just below the fermi level with subsequent alteration of the band gap

Recent Exotic Topotactic Modifications of Magnetic oxides

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Design of New Oxychalcogenides From Heteroleptic Building Blocks

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