Dissertations / Theses on the topic 'Approche statistique de la mécanique des fluides'
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Venaille, Antoine. "Mélange et circulation océanique : une approche par la physique statistique." Phd thesis, Grenoble 1, 2008. http://www.theses.fr/2008GRE10310.
Understanding how the small scales affect the large scales in oceans is an important issue for the description of surface currents and of the vertical structure of the oceans. The huge number of degrees of freedom involved in those problems makes any deterministic approach illusory. By contrast, the traditional tools of statistical mechanics allow to reduce those problems to the study of only a few parameters. In the first part, the equilibrium statistical mechanics of two-dimensional flows is applied to the study of simple ocean models. The second part is a phenomenological approach to turbulent mixing in stratified flows; the aim is to describe the temporal evolution of the probability to measure a certain value of the fluid density at a given depth
Venaille, Antoine. "Mélange et circulation océanique : une approche par la physique statistique." Phd thesis, Université Joseph Fourier (Grenoble), 2008. http://tel.archives-ouvertes.fr/tel-00347063.
Ottonelli, Claudio. "Apprentissage statistique de modèles réduits non-linéaires par approche expérimentale et design de contrôleurs robustes: le cas de la cavité ouverte." Phd thesis, Ecole Polytechnique X, 2014. http://pastel.archives-ouvertes.fr/pastel-01065782.
Fontaine, Côme. "Etude de deux modèles simplifiés de turbulence à l'aide du groupe de renormalisation fonctionnel : l'équation de Burgers et le modèle de Sabra." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALY083.
In this thesis, we focus on two simplified models describing turbulent flows. In these two models, the turbulent state exhibits scale-invariance and universal statistical properties resembling those of true hydrodynamical turbulence. This type of behaviour is very familiar in physics: it corresponds to a critical system. In this work, we use a widely used tool in the study of criticality: the functional renormalisation group (FRG). The first model, named the Sabra shell model, describes effective interactions among a discrete number of velocity modes of a turbulent fluid. This schematic description captures many essential properties of turbulent flows. In particular, the velocity field is multifractal. The way in which the dynamics generates this multifractality is still poorly understood from a theoretical perspective. In this thesis, we formulate a reverse renormalisation flow, meaning that we integrate out the largest scales first. Using this method, we find a fixed point of the renormalisation flow with anomalous scale invariance, relatively close to the expected value for certain observables. We show that it is clearly distinct from the fixed point obtained when all scales are forced, through a forcing with a power-law spectrum, which corresponds to the fixed point of the RG obtained in perturbation theory. The second model studied is the Burgers equation, which describes the dynamics of a fluid in the absence of pressure. We focus on the effect of a conservative noise on the velocity field. We prove the existence of a scale invariant regime with a critical dynamical exponent z=1 using an exact closure of the renormalisation flow equation. This closure relies on the existence of certain symmetries of the Burgers equation. Indications of the existence of this new scaling regime were previously found in numerical solutions of the Burgers equation. We provide in this thesis a theoretical proof of its existence and calculate the associated universal properties
Monchaux, Romain. "Approche statistique des écoulements turbulents." Paris 7, 2007. http://www.theses.fr/2007PA077206.
This work presents two studies based on the experimental von Karman flow. On the one side, we compare theoritical predictions obtained in the ideal case of a statistical mechanics derived for inviscid force-free axisymmetric flows to Stereoscopic Particule Imaging Velocimetry (SPIV) measurements. We get global relations characterizing the system's steady states and showing a tendency to velocity-vorticity alignement at high Reynolds numbers. On the other side, in the VKS collaboration, we study dynamo action in an unconstrained liquid sodium flow. This effet is an instability which is assumed to be responsible for astrophysic object's magnetic fields, the Earth's one for example. The VKS2 experiment has demonstrated for the first time a dynamo action leading to a wide variety of time-dependent dynamics: steady states, oscillations, intermittency and even randomly switching behaviours close to Earth's magnetic field are presented. We show that these different dynamics can be classified with respect to the experiment's Rossby number. We underline the links existing between hydrodynamic and magnetohydrodynamic bifurcations
Bonnifet, Valentin. "Prédiction du phénomène de tremblement sur un profil d'aile avec une approche LES de type PANS-RSM." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS389.
This PhD was devoted to develop a Large Eddy Simulation subgrid scale model based on transport equations. The subgrid scale model is built in the same manner as second order statistical model suggested by Gerolymos-Lo-Vallet-Younis. A constant control parameter has been introduced to tune the amount of turbulent kinetic energy handled by subgrid scale model. This parameter allows a bridging from Direct Numerical Simulation to Reynolds Averaged Navier-Stokes. This approach can correctly predict turbulent flow with coarser grid and time step than canonical Large Eddy Simulation based on algebraic subgrid scale models where subgrid length scale corresponds to Taylor micro scale. Indeed, the subgrid scale model handles a large part of turbulent kinetic energy in the boundary layer.Transonic flow simulation around OAT15A airfoil is carried out using the suggested approach. On particular inflow conditions, the shock-wave shows a self-sustained motion on the airfoil upper side resulting from the shock-wave boundary layer interaction. Reynolds Averaged Navier-Stokes is not able to predict averaged field because this large unsteadiness is undeterministic and an LES approach is needed. According to the results, the suggested approach can handle shock-wave motion. Filtered flow field, turbulent correlation and control parameter impact analysis are presented. Finally, development ways are suggested in order to improve the subgrid scale model using inhomogeneous control parameter in space and/or time
Agullo, Olivier. "Dynamique des tourbillons et statistique des vortex ponctuels." Aix-Marseille 1, 1997. http://www.theses.fr/1997AIX11067.
Lafon, Philippe. "Mélange laminaire de fluides miscibles en cuve agitée : approche numérique." Toulouse, INPT, 1989. http://www.theses.fr/1989INPT021G.
Ngot, Kongolo Joseph Christian. "Stabilité des gradins des exploitations à ciel ouvert : approche statistique mécanique et probabiliste." Vandoeuvre-les-Nancy, INPL, 1990. http://www.theses.fr/1990INPL050N.
Poli, Charles. "Chaos ondulatoire en milieux ouverts : approche statistique par la théorie des matrices aléatoires non-hermitiennes." Nice, 2009. http://www.theses.fr/2009NICE4091.
In the field of Wave Chaos, statistics of ideal closed systems are nowadays well understood. However, much less is known for open systems, namely for systems those coupling to environment cannot be neglected anymore. Applying the Random Matrix Theory to the formalism of the effective Hamiltonian, spectral and spatial statistics of open chaotic systems are investigated analytically. Furthermore, theoretical predictions are checked systematically through numerical simulations of random matrices. In the spectral domain, the modifications induced by the openness on the spacings and the avoided crossings are illustrated using the resonance trapping effect. The well-known distributions of spacings and avoided crossings are generalized to open chaotic systems that allow to explain results based on microwave experiments. In the spatial domain, statistics of the non-orthogonal parameter, which measures the impact of the openness on the eigenfunctions of the effective Hamiltonian, are derived analytically and verified by numerical simulations modelling chaotic complexness parameter for a given resonance, is also obtained. This finding is confirmed through electrodynamics experiments
Serra, Roger. "Sur une approche statistique de l'identification modale des structures." Besançon, 1999. http://www.theses.fr/1999BESA2055.
Feliachi, Ouassim. "From Particles to Fluids : A Large Deviation Theory Approach to Kinetic and Hydrodynamical Limits." Electronic Thesis or Diss., Orléans, 2023. http://www.theses.fr/2023ORLE1063.
The central problem of statistical physics is to understand how to describe a system with macroscopic equations, which are usually deterministic, starting from a microscopic description, which may be stochastic. This task requires taking at least two limits: a “large N ” limit and a “local equilibrium” limit. The former allows a system of N particles to be described by a phase-space distribution function, while the latter reflects the separation of time scales between the fast approach to local equilibrium and the slow evolution of hydrodynamic modes. When these two limits are taken, a deterministic macroscopic description is obtained. For both theoretical and modeling reasons (N is large but not infinite, the time-scale separation is not perfect), it is sometimes important to understand the fluctuations around this macroscopic description. Fluctuating hydrodynamics provides a framework for describing the evolution of macroscopic, coarse-grained fields while taking into account finite- particle-number induced fluctuations in the hydrodynamic limit. This thesis discusses the derivation of fluctuating hydrodynamics from the microscopic description of particle dynamics. The derivation of the fluctuating hydrodynamics is twofold. First, the “large N” limit must be refined to account for fluctuations beyond the average behavior of the system. This is done by using large deviation theory to establish kinetic large deviation principles that describe the probability of any evolution path for the empirical measure beyond the most probable path described by the kinetic equation. Then, the fluctuating hydrodynamics is derived by studying the hydrodynamical limit of the kinetic large deviation principle, or the associated fluctuating kinetic equation. This dissertation discusses this program and its application to several physical systems ranging from the dilute gas to active particles
Gouair, Hassan. "Approche probabiliste de la rupture fragile et ductile à grandes vitesses de déformations." Metz, 1994. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1994/Gouair.Hassan.SMZ9434.pdf.
In this work we have examined fracture initiations mechanisms on notches under dynamic loadings. Two kinds of fractures where examined : the brittle fracture of a glass and a molybdenum alloy TZM and the ductile fracture of a XC18 steel. Our work point out the interest of using notched specimens instead of craked specimens for fracture toughness evaluation and justifies the notch stress intensity factor approach. We have observed that the fracture mecanisms under static and dynamic loads are the same. However we have noticed an increase in the scattering of results in both types of fracture. This increase is explained by the multiactivation mecanism of structure defects. We have particulary shown this point for ductile fracture by observation of the number of cavity per fractured area. To solve this problem we have developped a microstatistic approach. Two possibilities are available : the numer of activated defects is unknown and a microstatistic model allows to know this number per volume unit from phenomenological results, the number of activated defects is experimentaly obtained and microstatistic allows to forsee phenomenological results. We have followed this approach in the case of ductile fracture of a steel. These two approaches although elementary got us promising results
Depardon, Sébastien. "Analyse topologique d'écoulements complexes : utilisation de la vélocimétrie par imagerie de particules pour une approche quantitative." Poitiers, 2006. http://www.theses.fr/2006POIT2280.
This thesis presents a topological analysis of 3-D bluff body flows. The skin-friction pattern topology around a wall-mounted cube is studied. Near-wall PIV is a valuable tool for this purpose, conbining the advantages of both global/qualitative and analytical/quantitative approaches of 3D separation. The 3D mean flow topology is extrapolated from an iterative analysis of the shear-stress pattern. A post-processing strategy of instantaneous velocity fields is also presented. Based on POD, automated critical point detection and topology classification algorithms, it enables to extract large scale dynamic behaviors of the flow from insufficiently time-resolved datasets. These methods are then applied to an industrial case : the analysis of the flow around a 1/4 scale car model. Not only is the extrapolation of the 3D flow structure from near-wall PIV data addressed, but also the link between near-wall topology and the wall-pressure distribution (i. E. Aerodynamic forces)
Maurel, Stéphane. "Étude par imagerie laser de la génération et de la rupture d'un écoulement tourbillonnaire compressé : situation modèle pour la validation de simulations aux grandes échelles dans les moteurs." Toulouse, INPT, 2001. http://www.theses.fr/2001INPT035H.
Bianco, Federico. "Theoretical and numerical analysis of the interaction between dynamics and chemistry in reactive flows." Paris 6, 2013. http://www.theses.fr/2013PA066243.
The thesis is divided in three parts. In the first part we investigate a nonlinear advection-diffusion-reaction equation for a passive scalar field. The purpose is to understand how compressible advection can affect the front dynamics and the bulk burning rate. The effect is quantitatively measured, and it turns out to be generally small. In the second part, reaction-diffusion processes in two-dimensional percolating structures are investigated. Two different problems are addressed: reaction spreading on a percolating cluster and front propagation in a percolating channel. For reaction spreading, numerical data show a power-law behavior of the reaction product. For percolating channels, a statistically stationary traveling wave develops. While the front speed is a low-fluctuating quantity and its behavior can be understood using a simple theoretical argument, the front width is a high-fluctuating quantity showing a power-law behavior as function of the channel size. In the third part, we study numerically the combustion instabilities that may appear in a micro-combustor. A one-dimensional and a two-dimensional (axially symmetric) constant density model, with one global reaction kinetic, are considered. The purpose of this analysis is to show how complex dynamics of combustion, in certain limits, can be captured by low-order models (chemically and gas-dinamically). Numerical results show a good qualitative agreement with experiments in a large range of regimes. In the end, we extend our analysis investigating the range of stability for different diameter of the combustor, and we show that dimensionality of the model can play a central role
Deveaux, Vincent. "Modèles markoviens partiellement orientés. Approche géométrique des Automates cellulaires probabilistes." Phd thesis, Université de Rouen, 2008. http://tel.archives-ouvertes.fr/tel-00325051.
Au cours de la première, nous définissons la notion de chaîne partiellement ordonnée qui généralise celle d'automate cellulaire probabiliste. Cette définition se fait par l'intermédiaire de spécification partiellement ordonnée de la même façon que les mesures de Gibbs sont définies à l'aide de spécifications. Nous obtenons des résultats analogues sur l'espace des phases : caractérisation des mesures extrêmes, construction/reconstruction en partant des noyaux sur un seul site, critères d'unicité. Les résultats sont appliqués tout au long du texte à des automates déjà connus.
La deuxième partie est essentiellement vouée à l'étude d'automates cellulaires unidimensionnels à deux voisins et deux états. Nous donnons deux décompositions des configurations spatio-temporelles en flot d'information. Ces flots ont une signification géométrique. De cela nous tirons deux critères d'unicité.
En annexe, nous donnons une démonstration de transition de phase d'un automate cellulaire défini par A. Toom, le modèle NEC. Tout au long du texte, des simulations sont présentées.
Carlier, Jean-Philippe. "Modélisation du transfert de masse en milieu poreux par approche stochastique." Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13171.
Application of stochastic methods to flow and transport in porous media allowed one to cast off one of the major difficulties encountered in field conditions : heterogeneity in parameters values (in particular for hydraulic conductivity) combined with scarcity of available data. Nevertheless, due to the complexity of equations to be solved, it has been necessary to work under some simplifying assumptions, mainly with regards to the nature of the medium and of the occurring flow. Thus, most of the existing results only apply to uniform flow, in infinite or semi-infinite and weakly heterogeneous media. The aim of the present work, focused on the injection/pumping doublet, commonly encountered in remediation schemes, is the study the impact on existing solutions for infinite medium of no flux finite boundaries. Two methods are adopted : one analytical based on the properties of potential functions, the other one based upon the theory of bayesian conditioning. . These two methods, compared one to another and both showing limitations, allow us to enlighten the necessity to take into account the domain's geometry, especially the relative positions of limits and wells. Another difficulty of the application of stochastic theories to concrete cases being statistical parameters identification, a sensitivity analysis is conducted upon the previous case, leading to definition of a sampling optimum for a pump-and-treat characterization test, and leading the way to inverse identification methods
Muller, René. "Comportement rhéologique et mesures d'orientation moléculaire de polymères à l'état fondu dans un écoulement élongationnel simple." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13102.
Muller, Florian. "Etude hydraulique et statistique d'écoulements métastables en faisceaux d'assemblage REP." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0588/document.
The analysis of fuel rod bundle flows constitute a key element of pressurized-water reactors safety studies. Indeed, an insufficient flow thermal mixing can lead to a boiling crisis, which is nefarious for the reactor safety. Numerous studies have shown the existence of reorganisation phenomena in the flow large-scale structures. This thesis work aims at improving our understanding of these phenomena, with the long-term goal of developing small-scales models suited for this type of flow. A bibliographic study has brought to light the challenges faced by simulations attempting to capture these phenomena, as well as various questions regarding their physical meaning. 3D simulations have been performed in order to study this flow ; they allowed to identify two reorganisation mechanisms for the large-scale structures consisting in a sign change for either a transverse velocity in rod-to-rod gaps or for a subchannel vortex. It appeared relevant to adopt a Taylor hypothesis in order to consider the evolution of large-scale 3D structures as transported-2D. A statistical method has then been applied to the 2D field in order to determine its thermodynamically-stable states in geometries with obstacles using the resolution of an optimization problem with a numerical calculation tool. Interesting similarities have been obtained between the PWR coherent structures and the stable states in a simplified 2D geometry. Further, 2D numerical simulations allowed to identify two different possible flow bifurcations. A parallel is drawn between these bifurcations and the two reorganizations observed in 3D simulations, laying the foundations for a physical explanation of this phenomenon
Deveaux, Vincent. "Modèles markoviens partiellement orientés. Approche géométrique des automates cellulaires probabilistes." Phd thesis, Rouen, 2008. http://www.theses.fr/2008ROUES004.
The global subject of this thesis is probabilistic cellular automata (PCA). It is divided into two parts. In the first part, we define the notion of partially ordered chains (POC) that generalise PCA. They are defined thought partially ordered specification (POS) in analogy with the statistical mechanics notion of Gibbs measure. We obtain the analogous of Gibbs measure phase space properties characterization of extremal measures, construction/reconstruction starting from single site kernels, criterion of uniqueness. These results are applied to some well-known PCA. The second part is essentially devoted to 1-dimensional PCA with two neighbours and two states. We show two decompositions of space-time configurations in flow of information. Those flows have a geometrical meaning that induce two uniqueness criteria. In appendix, we give a version of the proof of phase transition of the NEC Toom's PCA. The whole thesis is punctuated by simulations
Lafitte, Thomas. "Estimation simultanée des équilibres de phases et des propriétés dérivées de fluides complexex à l'aide d'une approche SAFT-VR." Pau, 2007. http://www.theses.fr/2007PAUU3032.
In this work a new equation of state based on the SAFT-VR theory (Statistical associating Fluid Theory for potential of variable range) adapted for the use of Mie potentials m-n is derived. The incorporation of this to model the repulsive and attractive interactions together with a new method for optimizing the molecular parameters allows now for an accurate description of vapour-liquid equilibria and derivative properties of complex fluids (isothermal compressibility, thermal expansivity, heat capacities, speed of sound, Joule-Thomson inversion phenomenon). The new equation of state improves significantly other models available in literature in the condensed liquid region. Moreover due to the sound physical meaning to the approach, no deterioration of the results is found for long chain molecules and a clear dependence of the characteristic molecular parameters with the increasing chain length is obtained. Taking into account the good results obtained for alkanes and the possibility of incorporating an association term in the equation, we have extended the scope of the study to associating coumpounds. We have found that the model is able to reproduce the complex behaviour of the isobaric heat capacity and thermal expansivity which display singularities due to the formation of aggregates. The accurate modelling of these two special features which are often considered as discriminatory tests for equation of states emphasize the consistency of the model proposed
Friggit, Jacques. "Mécanique statistique des marchés : une approche darwinienne des comportements financiers : application à la dynamique des taux de change." Aix-Marseille 3, 1995. http://www.theses.fr/1995AIX32020.
The dissertation models market behavior in very liquid markets. It assumes that financial behaviors adapt to information not instantaneously but following a darwinian evolution process, then reformulates and solves the problem thus posed by using tools borrowed from statistical mechanics. Some properties of the resulting price process are then compared to actual price processes observed in the foreign exchange market on short time scales. A potential predictor of instabilities is derived. A complete translation of the dissertation into english is available
Laurindo, João Borges. "Évaporation en milieu poreux : étude expérimentale sur milieux-modèles et modélisation de type percolation." Toulouse, INPT, 1996. http://www.theses.fr/1996INPT070H.
Carpy, Sabrina. "Contribution à la modélisation instationnaire de la turbulence : modélisations urans et hybride rans/les." Poitiers, 2006. http://www.theses.fr/2006POIT2342.
The aim of this work is to account for the unsteadiness effects on the turbulence in single point closure. The existence of large scale structures in statistically steady flows leads to reconsider some hypothesis. Much more than adding the time derivatives , the URANS equations needs to consider a new decomposition and an assiociated operator. Therefore, the applicability of usual closure methods has to be examined. For exemple, the periodicity of a synthetic jet leads to a non-equilibrium, which induces a permanent misalignment of anisotropy tensor and strain tensors. RSM are able to reproduce this misalignment, whereas k-ε. Model can't. A seamless hybrid RANS/LES method, based on the version of Schiestel's model, relies on transport equations for the subgrid stress (ij)SGS and dissipation. The decomposition operator is then assimilated as a filter with an adapatative cutoff frequency. The predictions obtained on a temporal mixing layer shows the ability of this model to capture the very large structure of the flow
Caillol, Jean-Michel. "Contribution à la théorie des fluides coulombiens et des solutions électrolytiques." Paris 11, 1987. http://www.theses.fr/1987PA112241.
Abboudi, Saïd. "Contribution à l'étude du transfert de chaleur, en régime instationnaire, entre parois et écoulement fluide en convection forcée, dans un conduit soumis à une condition de flux généralisée : approche numérique et détermination des coefficients de transfert "métal fluide" par thermographie infrarouge." Aix-Marseille 1, 1988. http://www.theses.fr/1988AIX11166.
Canivet, Eric. "Réconciliation et validation des mesures sur un système hydraulique complexe : le canal de Provence." Lyon 1, 2002. http://www.theses.fr/2002LYO10011.
Bouleux, François. "Approche discrète de l'évaporation en milieu poreux : étude de fronts stabilisés par les forces de gravité ou de viscosité en deux dimensions." Toulouse, INPT, 1999. http://www.theses.fr/1999INPT012H.
Darbani, Mohsen. "Approche sans maillage basée sur la Méthode des Eléments Naturels (NEM), pour les écoulements bidimensionnels à surface libre." Compiègne, 2009. http://www.theses.fr/2009COMP1851.
Solving equation with free surface often encounters numerical difficulties related to excessive mesh distortion as is the case of dambreak or breaking waves. In this work we explore the meshfree technique based on the Natural Element Method(NEM) to simulate the 2D fluid flow in presence of strong gradients. The equations considered here are those of Saint-Venant shallow water where we consider the full non-linear equations, with a transient flow under the Coriolis effect. The nonlinear terms are computed by using a Lagrangian technique based on the method of the characteristics. This will allow us to avoid setting up a numerical algorithm, like Newton-Raphson’s, which tend to extend the computing time. However, the management of boundary conditions remains a major difficulty in meshless methods. We have therefore defined a thin geometrical domain close to the boundaries and a domain for computing that will be submitted to nodal enrichment, when the particles leave the computational domain
Spinelli, Lionel. "Une approche topologique des transitions de phase." Aix-Marseille 1, 1999. http://www.theses.fr/1999AIX11042.
Faghani, Dariush. "Étude des structures tourbillonnaires de la zone proche d'un jet plan : approche non stationnaire multidimensionnelle." Toulouse, INPT, 1996. http://www.theses.fr/1996INPT096H.
Loubère, Raphaël. "Une méthode particulaire lagrangienne de type Galerkin discontinu : Application à la mécanique des fluides et l'interaction laser/plasma." Bordeaux 1, 2002. http://www.theses.fr/2002BOR12568.
Diet, Ambre. "Une approche de bout en bout du tolérancement statistique sous contraintes industrielles : contribution au jumeau virtuel industriel." Thesis, Toulouse 3, 2021. http://www.theses.fr/2021TOU30014.
In the manufacturing process of a product, various assembly steps are necessary. Several types of requirements have to be met at each level and involve considerations about dimensional uncertainties on the parts to be assembled. Tolerancing is the activity in charge of the management of these uncertainties and takes place both in the product development phase and in the series production phase. In the context of the aeronautics industry, in particular with regards to tolerancing on aerostructures, specificities have to be taken into account in the development of adequate methods and tools. Prior to production, one of the main issues of tolerancing amounts to allocate tolerance limits suited to a given acceptable scrap rate. The aim is to allow the actors concerned with tolerance intervals to agree on a consistent and robust tolerance value. A statistical methodology based on a Chernov bound approach applied to a sum of uniform distributions is proposed. In the production phase, the availability of measurement data allows to refine the statistical tolerancing approach. The linear model often considered can be corrected to serve new approaches. A methodology to manage acceptance criteria on tolerance values is proposed, basing the decision support on risk concepts pertinently defined for industrial actors. Within the framework of the revision of tolerance sharing in an assembly, an optimization problem is formulated with appropriate industrial costs in order to propose the optimal tolerance re-sharing in a stack chain. Finally, the proposed methodologies are implemented in tools allowing industrial processing and end-to-end management of tolerances from elementary parts to final product assembly, thus contributing to the elaboration of the product virtual twin
Queffeulou, Amélie. "Étude cinétique de la dégradation photocatalytique de composés organiques volatils (COV) et modélisation par une approche numérique de la mécanique des fluides." Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL068N/document.
VOCs are a source of discomfort for occupants and can have harmful effects on health. Photocatalysis is a promising process to remove these compounds. ArcelorMittal Liège Research has indeed developed TiOB2 Bthin film coated on steel which can be easily integrated into purification air systems. Objectives of this research are firstly, identifying parameters which influence the photocatalytic degradation of these VOCs using of such catalyst. Secondly, validate the possibility to predict performances of the photocatalytic reactor by combining fluid flow and photocatalytic reaction. An experimental set-up including an annular reactor has been designed and realized in order to conduct kinetic studies. Acetaldehyde has been chosen as a pollutant model and studied mainly with concentrations of few ppm ranges. Its conversion yield depends on pollutant concentration, relative humidity, temperature, UV light intensity and presence of others VOCs. Based on a theoretical surface model of the photocatalytic reaction, and using experimental data, this reaction is modelled. In order to predict performances of the photocatalytic reactor packed thin film of TiOB2B, a methodology which consists to combine fluid flow and photocatalytic reaction has been developed and validated. Space-time distribution of pollutant concentration is then determined with a computational fluid dynamics approach. Comparison between experimental data and numerical simulations obtained with a photocatalytic reactor at the laboratory scale and another one in semi-pilot scale are well satisfactory
Nguyen, Thi Thuy Linh. "Approche micromécanique du comportement d'une suspension de bulles dans un fluide à seuil." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1092/document.
This thesis contributes to characterizing the behavior of a suspension of bubbles dispersed in a non-Newtonian fluid (yield stress fluid type).It consists of three parts. The first part is a literature review identifying the theoretical and experimental works for bubbles sheared in a Newtonian material. The second part is dedicated to the experimental study of the simple shear of a bubble suspended in a yield stress fluid. The last part consists in developing an upscaling approach to study the macroscopic behavior of a suspension of bubbles in a yield stress fluid. For experimental work, we developped a first prototype of device for the study of the shearing of a bubble in a yield stress fluid. For that purpose, an air bubble is injected in a big volume of Carbopol sheared far from the bubble by a system in two parallel bands. A fist series of tests allowed to show the efficiency of the device and to obtain some results on the deformability of a sheared bubble in a yield stress fluid. For theoretical work, first we proposed estimates of the behavior of the suspension in the case of diluted scheme, Mori-Tanaka, autocoherent and morphological patterns. These models have allowed us to find that in the elastic regime the macroscopic elastic modulus of the suspension depends on the capillary number Caelast defined as the ratio of the shear modulus of the fluid suspended over the capillary pressure of the bubble. Then using a modified secant homogenization method (Suquet 1997), we estimated the overall nonlinear properties of the suspension. The model predicts that the overall yield stress of the suspension is that of the suspending fluid regardless of the size of bubbles. The validation of these micromechanical models was achieved thanks to the experimental results obtained in the laboratory (Ducloué 2014).Keywords: bubbles suspensions, yield stress fluid, rheology, capillary number, upscaling approach
Wallot, Louis Philippe. "Approche numérique bidimensionnelle de la convection naturelle dans une enceinte fermée : transition vers le chaos par quasi-périodicité." Perpignan, 2006. http://www.theses.fr/2006PERP0698.
The author numerically explores the road towards chaos by two-dimensional non stationary natural convection developing in a closed enclosure containing of the air, of square cross-section. The cavity is tilted of an angle of 15° have regard to the plane horizontal and heated by two opposite sides. This study showed that the system forwards towards chaos via three supercritical bifurcation of Hopf. By increase in the number of Rayleigh, the point limit attractor is destabilized and yields the place to an attractor cycle limit which, in its turn, loses its linear stability with the profit of an attractor torus T2. A phenomenon of fixing of frequency, rather fugacious, brings back this torus to an attractor cycle limit. This cycle is destabilized, again, thus giving rise to an attractor torus T2. It occurs a second phenomenon of fixing of frequency to the insue of which the dynamic evolution of the system becomes chaotic
Andreotti, Bruno. "Action et réaction entre étirement et rotation, du laminaire au turbulent." Paris 7, 1999. http://www.theses.fr/1999PA077004.
The dynamics of turbulence can be interpreted in terms of interaction between two components : stretching. Which corresponds to a local convergence (or divergence) of streamlines, and rotation. The effect of stretching on rotation is well known : rotation is amplified in a stretching direction and decreased in a compressive direction. The retroaction of rotation on stretching is studied experimentally, considering flows where particular interactions between stretching and rotation are constrained by geometry. The same mechanism of retroaction is observed in three experiments : if stretching amplifies rotation, rotation tends to reduce stretching. This mechanism is linked to the fact that pressure gradient, in a region of disturbed rotation, cannot completely balance centrifugai force. And tends to bring the flow back to a locally two-dimensional state. The action and reaction between stretching and rotation are at the origin of the relative stability of rotation dominated flows in comparison with those domianted by stretching. The instability of an hyperbolic flow is shown and characterised experimentally. Above a threshold £tiven by geometry, an alternats array of vortices aligned in the stretching direction appears. Once these vortices are formed, a réduction of stretching is observed in their core. Symmetrically, the stability of a large Reynolds number stretched vortex is studied by analysing the properties of velocity fluctuations in ifs vicinitv. A depletion of the tendencv to stretching, signature. In turbulence of an energy cascade, is observed. It is shown. As a conclusion, how a prohabilistic reformulation of simple dynamical mechanisms. As those which dominate the interaction between stretching and rotation, may lead to a type of modelling of turbulence dvnamics
Demuro, Antonietta. "La mécanique des fluides en France durant l’entre-deux-guerres : J. Kampé de Fériet et l'IMFL." Thesis, Lille 3, 2018. http://www.theses.fr/2018LIL3H032/document.
Joseph Kampé de Fériet (1893-1982), a French mathematician of Lille, was an international specialist in fluid mechanics and was director of the Institut de mécanique des fluides de Lille (IMFL) from its creation in 1929. By familiarizing himself with this field and by addressing questions of an experimental nature through his work on ballistics, during his scientific wartime service to the Gâvre Commission (1915-1919), this scientist played a triple role in the institute. As a mathematician, he made a remarkable contribution to Taylor-von Kármán's statistical theory of turbulence using the theory of random functions due to Kolmogorov, Khintchine, and Slutsky. As an experimental scientist, he took part in the experimental work of the IMFL aiming on one hand to study atmospheric turbulence and, on the other hand, to validate the ideas of the school of Philippe Wehrle and Georges Dedebant. This school was formed within the Atmospheric Turbulence Commission, created by the Minister of Air in 1935. Finally, as director of the institute, he strengthened links with industry and society in Lille, in the same way that he reinforced links with military officers during his work in Gâvre.In our thesis, we will use the scientific and institutional career path of J. Kampé de Fériet – from his service at Gâvre (1915) up until the year of his resignation as director of the IMFL (1945) - as a prism by which we will answer further questions of a more general nature regarding fluid mechanics in France during the first half of the twentieth century. Some but not all of these considerations bring to light new elements that are common to ballistics and to other areas of applied mathematics
Fezzani, Riadh. "Approche parallèle pour l'estimation du flot optique par méthode variationnelle." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00713970.
Besson, Ugo. "Une approche mésoscopique pour l'enseignement de la statique des fluides : étude des raisonnements des apprenants, élaboration et expérimentation d'une séquence d'enseignement." Paris 7, 2001. http://www.theses.fr/2001PA070033.
This thesis presents: a study of the forms of reasoning learners apply when dealing with fluids; the design, experimentation and evaluation of a teaching sequence on the static of fluids in the presence of gravity, kinetic and thermal aspects excluded. It contains an analysis of previous research on this topic by other authors; and some guiding ideas on the reasoning involved in this context. Content analysis and the study of conceptions are linked throughout. Besides two preliminary interviews, the research on reasoning involves several questionnaires put to high school and first-year university students. One crucial point is a difficulty in connecting local actions and global effects; this requires a systemic form of reasoning, to explain the mechanism establishing the final situation of equilibrium. The short teaching sequence experimented among first-year university students is based on a simple mechanical model of fluids, at the mesoscopic level, using sponge balls as elements. The aim is to make concrete and visual the typical decomposition of the mechanics of fluids, using objects through which a behavioural analogy can be established. . . Established (Attention is drawn to local interactions and a transmission of changes, to help students overcome the difficulty of conciliating certain formal laws and the local behaviour of fluids. The sequence is evaluated by means of paper-and-pencil questionnaires as pre-tests and post-tests, whose results are compared against those of "classically" taught control groups, and by studying the transcripts of the student debates that were held in the final session. The observations of a group of trainee-teachers are given, regarding the implementation of the sequence in class. Some directions for developing the research are suggested at the end of the thesis
Seshasayanan, Kannabiran. "Rotating turbulent dynamos." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066158/document.
In this thesis, we study the effect of rotating turbulent flows on the dynamo instability. We study the different limits of rotating turbulence using numerical simulations and theoretical tools. We first look at the dynamo instability driven by quasi-twodimensional flows (flows with three components varying along two directions), which models the limit of very fast rotation. We look at the saturation amplitude of the magnetic field as a function of the magnetic Prandtl number for such flows. A theoretical model for the dynamo instability is later developed and compared with the numerical results. We also study the effect of a fluctuating velocity field on the growth rate of different moments of the magnetic field. The three dimensional rotating flow is then studied for different range of parameters. For the hydrodynamic problem, we study the transition to an inverse cascade and the different saturation mechanism of the inverse cascade. Later the dynamoinstability driven by such flows is investigated. We show that the effect of rotation modifies the most unstable mode and in some cases can reduce the dynamo threshold
Saint-Michel, Brice. "L'écoulement de von Kármán comme paradigme de la physique statistique hors de l'équilibre." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00911544.
Maurer, Paco. "Approche expérimentale de la dynamique non-linéaire d'ondes internes en rotation." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN014/document.
Through their instabilities, internal gravity waves, which propagate in stratified fluids, play a paramount role in the oceanic dynamics. Indeed, their instabilities transfer energy to small scales and lead to mixing. Among these instabilities, we studied the triadic resonant instability (TRI). This process is characterized by the generation from a primary wave of two secondary internal waves, whose frequencies and wave vectors fulfill the spatial and time resonance conditions. If the fluid is also rotating (which is in generally the case in geophysics), rotation changes not only the properties of internal waves, which, in this case, are named inertia-gravity waves, but also the properties of the TRI. The experimental study on a rotating plateform of the instability of a controlled internal wave beam highlighted the role played by rotation on TRI features, such as the instability threshold or the characteristics of the secondary waves. Moreover, these results are in excellent agreement with an asymptotic development of the instability that takes into account the finite width of the wave beam, key parameter in a laboratory and oceanic context. this effect is responsible for the existence of a critical latitude in the ocean.In a second part of this work, we built a new wave generator, which allowed for the study of tridimensional axisymmetric waves. The axisymmetric modes generated by this new set-up were characterized and compared to analytical solutions. The generator can also produce a localized axisymmetric bump which focalises the wave in the center of the tank. By changing the group velocity of the waves, through a non-linear stratification, we are able to create a large energy build-up at the point of focalisation. Depending on the amplitude of the wave, we observe the transition from a stable state to a strongly unstable one
Bereaux, Yves. "Procédés de Plasturgie : Approche par des modèles numériques, thermiques et mécaniques." Habilitation à diriger des recherches, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-01023401.
Le, Moullec Yann. "Comparaison des approches systémique, mécanique des fluides numérique et compartimentale pour la modélisation des réacteurs : application à un réacteur canal à boues activées." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL053N/document.
The purpose of this work is the comparison of the systemic, computational fluid dynamics (CFD) and compartmental approaches. This last approach is a new method of model construction based on the quantitative results of a CFD simulation. A methodology to build such a model is described. These three modelisation approaches have been used to model a bench scale activated sludge wastewater treatment reactor : a complex biological tree-phase reactor (gas/liquid/floc). The CFD modelling has been validated with velocity and turbulence fields, obtained with laser doppler velocimétry and with void fraction measurements obtained with an optical probe. The global hydrodynamics of the reactor is well represented by a plug flow model with axial dispersion. This behaviour is well represented by CFD simulation of residence time distribution. Experiments on the bench scale activated sludge reactor fed with a synthetic substrate primarily composed of Viandox have been carried out. Biological reactions have been modelled by the ASM1 model developped by IWA. Evolution of almost all the concentrations along the reactor are simulated with a maximum error of 25 \% with systemic and CFD models. Some differences are highlighted between these two models. The compartmental model gives almost the same results as the CFD model with a calculation time from 10 to 20 times shorter. Moreover this compartment model is as easy to handle as the sytemic model and allows a better understanding of the phenomena which take place in the reactor than the CFD model
Al-Izzi, Sami. "Dynamics of lipid membrane tubes." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS674.
Membrane tubes are structures ubiquitous in cells, and understanding their dynamics and morphology is of vital importance for cellular biophysics. This thesis will discuss several aspects of the dynamics of membrane tubes in situations where they are driven out of equilibrium by various biologically inspired processes. We analyse the inflation of membrane tubes and their subsequent instability due to ion pumps driving an osmotic pressure difference. This is inspired by the structure of an organelle called the contractile vacuole complex, and leads to a new instability with a much longer natural wavelength than a typical Pearling instability. The stability of membrane tubes with a shear in the membrane flow is analysed and a novel helical instability which acts to amplify the fluctuations is found. We discuss the relevance of this instability in the process of Dynamin mediated tube scission. Finally we consider the dynamics and fluctuations of a membrane tube with active forces acting on it
Laage, de Meux Benoît de. "Modélisation des écoulements turbulents en rotation et en présence de transferts thermiques par approche hybride RANS/LES zonale." Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2012. https://theses.hal.science/docs/00/74/35/42/PDF/these_de_Laage.pdf.
The numerical simulation of turbulent flows in cooling system of hydrau- lic pumps sealing requires considering large computational domains and long integration times. The zonal hybrid RANS/LES modelling of turbulence could deal with such appli- cations, in order to reproduce the whole thermal and dynamical phenomena of the flow, with a computational cost compatible with industrial studies. This approach aims at pro- perly interfacing a Large Eddy Simulation (LES), which provides an accurate unsteady description of turbulence in some critical regions of the flow, with the statistical RANS approach, less demanding in computational resources, applied in the whole remaining fluid domain in order to take into account the imposed global variations of the flow (cool water injection in hot water, shaft and rotor rotation,. . . ). To this end, a detailed study of tur- bulence models appropriate for rotating flows is presented, following both the RANS and the LES approaches. Numerous turbulence models are compared in the rotating channel flow test case. The zonal coupling at boundary faces using the Synthetic Eddy Method (SEM) is studied and an innovative volumic coupling using a source term on overlapping RANS/LES area, the Anisotropic Linear Forcing, is proposed. For the first time, these two coupling methods are extended to heat transfer. The present zonal hybrid RANS/LES computations of static or rotating channel flows in isothermal or forced convection regimes, show the applicability of such modelling for industrial studies
Buron, Franck. "Etude d'une nouvelle approche de la méthode Particle-In-Cell pour le calcul d'écoulements instationnaires incompressibles tridimensionnels de fluide parfait ; application au cas de la plaque plane en incidence." Poitiers, 2000. http://www.theses.fr/2000POIT2255.
Lecointre, Pierre. "A la recherche de la texture hydrophobe, et quelques effets collectifs dans les milieux granulaires et en économie." Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAX009.
Fog or hot water can destroy the superhydrophobic properties of a textured surface owing to the condensation inside the texture. However, it was recently shown that such surfaces covered with cones at a scale of hundred nanometers could resist fog: condensed droplets can be ejected during their coalescence. We first experimentally show by electronic microscopy that a conical texture enables water drops to remain in a “fakir state”, even at a very small scale. We then studied different families of cone-textured surfaces by varying the spacing and the texture height. At the nanoscale, we showed that the texture size has a low influence on the antifogging efficiency whose limits rather lie in the water properties themselves, especially its viscosity. At the microscale, we described new situations where spontaneous ejection of condensed drops occurs despite a local trapping of water. We also studied the trajectory of expelled drops on such surfaces and confirmed that viscous effects play a major role in their ballistics. Finally, we focused on the ability of superhydropho- bic surfaces to repel hot water, a challenging situation for which we identified two independent recipes. In the second part of the thesis, we studied the ability of wetted fibers to capture dust. We showed that the quantities of captured particles is only influenced by the quantity of oil deposited on the fiber and not by its configuration (film or drop) on the fiber, unlike the growth kinetics of the aggregate where large differences are observed between the two configurations. The last part of the thesis focused on the Slutsky equation, a classical equation encountered in microeconomics. We described how the Slutsky matrix is modified when challenging classical economics hypotheses such as irrationality, interactions between goods or agents’ heterogeneity, and how it exhibits surprising features not predicted by consumer choice theory. The three parts can be addressed independently