Дисертації з теми "Dynamique des fluides – Vélocimétrie par images de particules"
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Funfschilling, Denis. "Dynamique de bulles dans des fluides rhéologiquement complexes." Vandoeuvre-les-Nancy, INPL, 1999. http://docnum.univ-lorraine.fr/public/INPL_T_1999_FUNFSCHILLING_D.pdf.
Повний текст джерелаLacroix, Thomas. "Performances et limites de la mesure de vitesse par la vélocimétrie laser par corrélation : application à des milieux optiquement denses." Rouen, 2014. http://www.theses.fr/2014ROUES035.
Повний текст джерелаEnvironmental standards in terms of pollution and consumption require an optimal injection, with a control of the size of the droplets, of their spatial distribution, and of the quantity of the liquid injected. The numerical calculations modeling the behavior of the spray need measuring points validating the initial conditions of the atomization process. Experimental measurements in the near injector outlet are necessary, because this is where grow instabilities, leading to the rupture of the spray. Most conventional measurement techniques become ineffective in this region by the high concentration of liquid droplets, their high velocity and especially their random shape (ligaments or non-spherical droplets). This work focuses on the Laser Correlation Velocimetry (LCV), an optical technique for measuring the velocity of the spray in the near injector outlet. This technique has the advantage of being implemented with a relatively simple installation and requires no assumptions about the shape of the liquid elements passing through the measurement volumes. Measurements have been made on a gasoline injector and on a triple disc injector, which have been characterized by PDPA and in terms of granulometry respectively. Imaging techniques coupled to the LCV technique allowed visualization of the measured flow. By comparing the liquid fraction in the images with the signals recorded at the same time, the goal was to establish a link between the collected signal and the morphology of the spray, and to link the measured velocity to the properties of the spray. Finally, information on the spatial, temporal and in terms of optical density have been noted, to evaluate the operating limits of the LCV technique
Boualia, Hassan. "Etude numérique et expérimentale des champs dynamiques et scalaires dans un écoulement turbulent fourni par un brûleur coaxial. Effet de la stratification." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR129/document.
Повний текст джерелаRésumé non fourni
Mouhali, Waleed. "Etude d'un écoulement forcé par précession : transition vers la turbulence et applications à l'effet dynamo." Paris 7, 2009. http://www.theses.fr/2009PA077242.
Повний текст джерелаThis thesis is the study of hydrodynamic flow in a cylindrical precession. This study brings together aspects of analytical (non-linear coupling) and experimental (PIV). The results are promising for a dynamo
Danlos, Amélie. "Dynamique des jets contrôlés : Application à l’étude du mélange dans des écoulements de jets annulaires à très grand rapport de diamètres." Phd thesis, Rouen, 2009. http://www.theses.fr/2009ROUES055.
Повний текст джерелаFavelier, Thomas. "Couplage de la vélocimétrie par images de particules en deux temps avec la décomposition en modes propres pour la caractérisation d'un écoulement." Phd thesis, Université Claude Bernard - Lyon I, 2006. http://tel.archives-ouvertes.fr/tel-00080473.
Повний текст джерелаUne étude expérimentale de l'écoulement bidimensionnel en moyenne en aval d'un cylindre semi-circulaire, par vélocimétrie par image de particules en deux temps (PIV2T) caractérise l'écoulement
Une analyse POD du champ de vitesse permet d'extraire les modes spatiaux et de définir un paramètre de phase décrivant l'instationnarité à grande échelle qui régit la partie déterministe. La modélisation de l'évolution temporelle des coefficients associés aux modes s'effectue par des fonctions soit harmoniques pour la partie déterministe, soit stochastiques pour la partie aléatoire.
La modélisation est en accord avec les mesures expérimentales des premiers moments statistiques en un point et des fonctions de corrélation spatio-temporelle du champ de vitesse.
Kuhlmann, Abrantes Juliana. "Vélocimétrie par Image de Particules Holographique pour les Mesures de Turbulence de Paroi." Phd thesis, Ecole Centrale de Lille, 2012. http://tel.archives-ouvertes.fr/tel-00862796.
Повний текст джерелаDérian, Pierre. "Wavelets and Fluid Motion Estimation." Rennes 1, 2012. https://ecm.univ-rennes1.fr/nuxeo/site/esupversions/5cdcde8f-715b-4725-a6d4-4eea6474aead.
Повний текст джерелаThis work falls within the general problematic of designing measurement tools adapted to the specificities of fluid flows. The development of digital imaging, combined with visualization techniques commonly employed in experimental fluid dynamics, enables to extract the apparent flow motion from image sequences, thanks to computer vision methods. The objective is to propose a novel “optical flow” algorithm dedicated to the multiscale motion estimation of fluid flows, using a wavelet representation of the unknown motion field. This wavelet formulation introduces a multiscale framework, conveniently adapted both to the optical flow estimation and to the representation of turbulent motion fields. It enables as well to design divergence-free bases, thereby respecting a constraint given by fluid dynamics. Several regularization schemes are proposed; the simplest consists in truncating the basis at fine scales, while the most complex builds high-order schemes from the connection coefficients of the wavelet basis. Proposed methods are evaluated on synthetic images in the first place, then on actual experimental images of characteristic fluid flows. Results are compared to those given by the usual “cross-correlations”, highlighting the advantages and limits of the wavelet-based estimator
Roy, Clément. "Dynamique et stabilité de tourbillons avec écoulement axial." Phd thesis, Université de Provence - Aix-Marseille I, 2008. http://tel.archives-ouvertes.fr/tel-00436894.
Повний текст джерелаYoussef, Jean. "Étude expérimentale d'un jet plan turbulent se développant dans un flux uniforme en co-courant." Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2012. http://tel.archives-ouvertes.fr/tel-00784840.
Повний текст джерелаBeaulieu, Sébastien. "Étude expérimentale par la technique PIV de l'écoulement dans le canal inter-aube d'une turbine axiale de type hélice." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27758/27758.pdf.
Повний текст джерелаCapiaux, Sylvie. "Application et développement de la vélocimétrie par images de particules pour l'étude de la phase d'admission dans les moteurs à allumage commandé." Rouen, 1997. http://www.theses.fr/1997ROUES068.
Повний текст джерелаRouland, Eric. "Etude et développement de la technique de vélocimétrie par intercorrélation d'images de particules. Application aux écoulements en tunnel hydrodynamique." Rouen, 1994. http://www.theses.fr/1994ROUES078.
Повний текст джерелаJarrahi, Khameneh Mojtaba. "Intensification du mélange par advection chaotique pulsée." Nantes, 2010. https://archive.bu.univ-nantes.fr/pollux/show/show?id=33a6dbf5-3e54-4105-a044-5387a8986d1b.
Повний текст джерелаThe purpose of this study is to investigate mixing enhancement by superposition of a temporal dependence, in the form of a pulsation, on a twisted pipe flow where the trajectories of fluid particles are spatially chaotic. In the steady case, the secondary flow in a curved tube is composed of two counter-rotating cells (Dean cells), however, the temporal dependence of the flow can make this structure more complex. This modification of the secondary flow which results in stronger velocity gradients enhances stretching and folding (the main mechanism of mixing). Here, the chaotic configuration is composed of six alternating 90° curved pipes. When a pulsating (steady+sinusoidal) flow passes through this geometry, the velocity field is measured by particle image velocimetry (PIV) for different pulsating conditions. To obviate light-refraction effects during PIV measurements, a T-shaped end channel is installed at the exit of the curved pipe. Experiments are carried out for the steady Reynolds numbers range 420≤Rest≤1000, velocity component ratios 1≤ (β = Umax,sin / Ust) ≤ 4 and frequency parameters 8. 37≤(α=r0(ω/ν)0. 5)≤24. 5. The effects of each parameter (Rest, β and α) on transverse mixing are discussed by comparing the dimensionless vorticity (|ζP|/|ζS|) and dimensionless transverse strain rates (|εP|/|εS|) during a complete oscillation period. The results show that β ≥ 2 and α ≤ 15 are favorable pulsating conditions for mixing enhancement. Moreover, in some pulsation conditions, the cells’ centers visit a zone (in the flow cross-section) 9 times larger that that of the steady case
Vigié, Franc. "Étude expérimentale d'un écoulement à surface libre au-dessus d'un obstacle." Toulouse, INPT, 2005. http://ethesis.inp-toulouse.fr/archive/00001382/.
Повний текст джерелаFree-surface flows over a single two-dimensional obstacle placed on the channel bottom wall are investigated in this work. The main objective is to determine the obstacle role and its influence on the flow dynamics. Two obstacles, a semi-cylinder and a flat gaussian one are used in this work. For both obstacles, free-surface profiles in the channel centerline are performed using water depth measurements. These profiles are classified in surface waves regimes, depending on the flow parameters: the Froude number and the blocking factor, which compares the height and the undisturbed water depth. Hydrodynamic in the obstacle vicinity is characterized with two-dimensional velocity fields measurements. Mean-velocity-field topology and the turbulence structure are analysed. Some of physical mechanisms, which control the free-surface shape and the local structure of the flow are exhibited
Albugues, Laurent. "Analyse expérimentale et numérique d'un jet débouchant dans un écoulement transverse." Toulouse, ENSAE, 2005. http://www.theses.fr/2005ESAE0001.
Повний текст джерелаDelay, Guillaume. "Analyse des écoulements transitoires dans les systèmes d'injection directe essence : effets sur l'entraînement d'air instationnaire du spray." Phd thesis, Toulouse, INPT, 2005. http://oatao.univ-toulouse.fr/7367/1/delay1.pdf.
Повний текст джерелаSteinmann, Thomas. "Métrologie optique en dynamique des fluides appliquées à l'écologie physique des insectes." Thesis, Tours, 2017. http://www.theses.fr/2017TOUR4050/document.
Повний текст джерелаFlow sensing is used by a vast number of animals in various ecological contexts, from preypredator interactions to mate selection, and orientation to flow itself. Among these animals, crickets use hundreds of filiform hairs on two cerci as an early warning system to detect remote potential predators. Over the years, the cricket hairs have been described as the most sensitive sensor in the animal kingdom. The energy necessary for the emission of an action potential by its sensory neuron was estimated to be a tenth of the energy of a photon. This PhD thesis aims to describe recent technological advances in the measurement and model of flows around biological and artificial flow sensors in the context of organismal sensory ecology. The study and understanding of the performance of sensory systems requires a high spatial precision of non-intrusive measurement methods. Thus, non-contacting measurement methods such as and Particle Image Velocimetry (PIV), originally developed by aerodynamics and fluid mechanics engineers, have been used to measure flows of biological relevance. The viscous oscillatory boundary layer surrounding filiform hairs has been visualized and used as input to model the mechanical response of these hairs, described as second order mechanical systems. The viscous hydrodynamic coupling occurring within hair canopy was also characterized using PIV measurements on biomimetic micro-electro-mechanical systems (MEMS) hairs, mimicking biological ones. Using PIV, we have also measured the air flow upstream of hunting spiders. We prove that this flow is highly conspicuous aerodynamically, due to substantial air displacement detectable up to several centimeters in front of the running predator. This disturbance of upstream air flows were also assessed by computational fluid dynamics (CFD) with the finite elements method (FEM). The development of non-intrusive measurement and CFD methods and their application to the analysis of the biological flow involved in cricket sensory ecology allowed us to revisit the extreme sensitivity of cricket filiform hairs. We predicted strong hydrodynamic coupling within natural hair canopies and we addressed why hairs are packed together at such high densities, particularly given the exquisite sensitivity of a single hair. We also proposed a new model of hair deflection during the arrival of a predator, by taking into account both the initial and long-term aspects of the flow pattern produced by a lunging predator. We conclude that the length heterogeneity of the hair canopy mirrors the flow complexity of an entire attack, from launch to grasp
Gagnon, Jean-Mathieu. "Contribution to the study of the 3D unsteady flow in a propeller turbine." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/28126/28126.pdf.
Повний текст джерелаReyt, Ida. "Écoulements induits en guide d'onde acoustique fort niveau." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2292/document.
Повний текст джерелаHigh amplitude acoustic propagation in a guide is associated with several non linear phenomena including acoustic streaming, discontinuity effects and transition to turbulence. Those phenomena are studied in this work and are all associated with acoustically induced flows. The present experimental study therefore is based on velocimetry laser techniques: Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV), wich are fitted to the measurement of the different flow velocity components. Firstly, PIV measurements at the exit of a convergent enable to complement previous LDV measurements. Then, in order to a better understanding of the specificity of transition to turbulence in acoustics, the evolution of the Stokes boundary layer is studied for increasing acoustic velocity amplitudes. Then an experimental study of acoustic streaming in a square channel is reported, and the influence of the geometry is examined. Moreover, the evolution of acoustic streaming vortices in a cylindrical waveguide is analyzed for fast streaming and some parameters that could control such evolution are modified. The harmonicdistribution inside the guide is changed and then the influence of thermal conditions is studied by coupling velocity measurements and mean temperature measurements inside the waveguide and along the wall. Some comparisons between measured streaming velocities and numerical simulation results are presented
Schaeffer, Eric. "Modèles régularisés locaux pour l'analyse de scènes dynamiques : application au traitement d'images et à la mécanique des fluides." Toulouse, ENSAE, 1997. http://www.theses.fr/1997ESAE0017.
Повний текст джерелаDuriez, Thomas. "Application des générateurs de vortex au contrôle d'Écoulements décollés." Phd thesis, Université Paris-Diderot - Paris VII, 2009. http://pastel.archives-ouvertes.fr/pastel-00005691.
Повний текст джерелаBordes, Guilhem. "Interactions non-linéaires d'ondes et tourbillons en milieu stratifié ou tournant." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00733175.
Повний текст джерелаMaillard, Mathilde. "Étalements de fluides à seuil." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1111/document.
Повний текст джерелаYield stress fluids are used in various industrial processes in which solid tools make them flow. To have a better understanding on how they spread on surfaces, we first studied the vertical coating on a thin plate and then the horizontal blade-coating. Both studies are based on macroscopic measures recording the force applied on the plate and on the microscopic determination on the velocity fields in the fluid by PIV. Numerical simulations based on cone programming, which validity had been confirmed in comparison to our experimental results, specified the flows at stake. In dip-coating, we observed than within our framework, the yield stress fluid deposit on the plate is millimetric and of constant thickness, except on the tips. According to the value of the viscous over plastic forces ratio, the coating is led by a "yield-gravity" or a "visco-gravity" balance. Then, we characterized the flow generated in the bath by the plate displacement in order to clarify the origin of the coating phenomenon. The numerical simulations specified the flow characteristics. The horizontal blade-coating in a channel involves the displacement of a weakly sheared cluster of fluid in relation to a part of fluid at rest, through a sheared layer. We showed that the growing dynamic of the cluster is described with a simple model which links it to the normal force to the plate
Lecerf, Arnaud. "Développement de la PIV stéréoscopique : Application à l'étude de la propagation de flamme en milieu confiné." Rouen, 2000. http://www.theses.fr/2000ROUES074.
Повний текст джерелаThis dissertation presents the development and the application of an optical diagnostic permitting to get an instantaneous cartography of the three components of velocity in a plan. This type of diagnostic is destined to a better understanding of greatly unstationary flows as those met in an industrial context (internal combustion engines, jets, flames). This method is based on a stereoscopic principle of imagery that, by cross-correlation of couples of particle pictures (PIV), permits to extract the 3D displacement of tracers in a flow inside a volume limited by the thickness of a laser sheet. In the first stage, tests have been driven on simple flows in order to validate our measurement technique and the whole developed system in real conditions. Our defined stereoscopic system in a configuration where the angle of view is limited, correctly describes a grid-turbulent flow and the big 3D structures (swirl typeflow). The application to the propagation of flame in a closed medium, showed that it is possible to consider some local studies on the behaviour of flame fronts (phenomena of delocalisation and convection). The characterization of a tumble-type flow illustrates the perspectives in the understanding of 3D movements of large scale organized structure. In turbulent flows met in engines, it is clear that the concept of swirl or tumble based on average measurements is not acceptable and the “average” data bases are not able to validate numerical results. It is therefore necessary to model the turbulent flows through its intensity and 3D structure shape as well as its instabilities met in every individual cycle
Gomit, Guillaume. "Développement de techniques de mesure de surfaces libres par moyens optiques : Application à l'analyse de l'écoulement généré par un modèle de bateau en bassin des carènes." Phd thesis, Université de Poitiers, 2013. http://tel.archives-ouvertes.fr/tel-01062934.
Повний текст джерелаJaffar-Bandjee, Mourad. "Pheromone transport in multiscale pectinate antennae." Thesis, Tours, 2019. http://www.theses.fr/2019TOUR4021.
Повний текст джерелаIn many moth species, female adults release tiny amounts of sexual pheromone in order to attract male mates and reproduce. The quantity of released pheromone is around a few dozens of nanograms and male moths can detect it a few hundred meters away from females. As a consequence, they must be able to smell very low concentrations of pheromone. This olfactory function is carried out by the antennae. A critical step in the olfactory process is the capture of molecules from the air. This is a mass transport problem which depends heavily on the shape of the antenna. One of the most spectacular shapes, which occurs in several moth families, is the pectinate antenna. This type of antenna is also thought to be more effective at detecting pheromones than cylindrical-shaped ones. In this work, we investigated whether and how the shape of the pectinate antenna influences its efficiency at capturing pheromone molecules. We focused on one species, Samia cynthia.A pectinate antenna is a complex and multi-scale object. It has a length of 1cm and is composed of one main branch, the flagellum, which carries secondary branches, the rami. Each rami supports numerous hairs, the sensilla, which are 150µm long and have a diameter of only 3µm. Thus, the characteristic dimensions of the antenna span over four orders of magnitude, which makes the study of such objects difficult.To simplify our problem, we decided to split the pectinate antenna in two levels: the macrostructure, composed of the flagellum and the rami, and the microstructure, composed of a rami and the sensilla it bears. Both structures were scaled up and fabricated by Additive Manufacturing. The building of the rami and sensilla, which are long and thin cylinders, was a challenge as we reached the limits of the 3D-printers we used.Pectinate antenna are permeable objects, as are the macro-and microstructures. Thus, air flowing in the direction of such objects either passes through the antenna or is deflected around it. Leakiness if the proportion of flow passing through the permeable object. This parameter is important as it sets an upper limit on the pheromone captured by the antenna: molecules carried by the deflected part of the flow cannot be captured. We experimentally determined the leakiness of the macro- and microstructures at several air velocities encountered by a moth in nature using Particle Image Velocimetry.We then calculated the pheromone capture and efficiency of the microstructure by adapting a model of heat transfer to our mass transport problem. We showed that the longitudinal orientation of the sensilla is sufficient to explain the phenomenon of olfactory lens, stating that the tip of the sensilla captures more molecules than the base. We also found that the efficiency of the antenna is limited by both the leakiness of the antenna, which increases with air velocity, and the local capture, which is the proportion of molecules captured in the part of the airflow passing through the antenna and which decreases with air velocity. Eventually, the microstructure does not have a strong maximum efficiency at a specific air velocity but, instead, is moderately efficient over the large range of air velocity encountered by a moth.We developed a method with the help of FEM simulations to combine the two levels (the macrostructure and the microstructure). This method is based on the relation between drag and leakiness and allowed us to determine the leakiness of the entire antenna. We then could calculate the efficiency of the pectinate antenna and compared it with the one of a cylindrical-shaped one. We found that a pectinate design is a good solution to increase the surface contact between the air and the antenna strongly while maintaining a good capture efficiency at the velocities encountered by the moth
Rigal, Claire. "Comportement de fluides complexes sous écoulement : approche expérimentale par résonance magnétique nucléaire et techniques optiques et simulations numériques." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0091/document.
Повний текст джерелаThis thesis is an experimental and numerical study of structured fluids bidimensional flows in a cylindrical pipe with singularity and in an annular geometry with eccentric cylinders. The objective of this thesis is to characterize the influence of the shear thinning properties on the recirculation zones by using efficient and non-intrusive techniques: particle image velocimetry and velocimetry by nuclear magnetic resonance imaging. Materials are xanthane solutions at different concentrations. In the first part, we determine the rheological and viscoelastic properties of the fluids used. The second part concerns the measured velocity field. It is shown that the shear thinning behavior have a strongly influence on the structure and the morphology of these flows and the pattern of the recirculation zones. Simultaneously, numerical simulations performed by Fluent and using the rheological behavior. A good concordance is observed between the experimental and numerical results. For the flows considered here, this comparison allows to validate the computational code and the behavior law used in the numerical simulations and modelling by a Cross model
Hetru, Laurent. "Etude expérimentale et numérique de l'interaction aérodynamique entre deux profils : application au risque aéronautique du décrochage profond." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4754/document.
Повний текст джерелаDeep stall is a specific type of airplane stall, in which the horizontal tail is inside the detached wake of the main wing. The tail loses its efficiency, leading to a stable pitching equilibrium position with a high angle-of-attack, without any easy recovery procedure. The aim of the study is to characterize the aerodynamic associated to that phenomenon in order to propose an identification and recovery procedure. The approach consists in a two-dimensional flow characterization based on an aeronautical reference configuration. Aerodynamic coefficients, obtained for a wide range of angles-of-attack, show the interaction between the airfoils on the stall of the downstream airfoil. The analysis of velocity fields gives the width and the axial development of the airfoils wakes. Phase-averages of velocity fields lead to the synthesis of flow time-development. With these results, a potential model of flow forcing on the downstream airfoil explains the lift coefficient alteration imposed by the interaction. Flow numerical simulations, giving time-resolved fields, provide good accordance with experimental developments .The whole set of results is used, concurrently with real aircraft data, inside a longitudinal flight model in order to analyze the airplane dynamical behavior. Criteria for the identification of the dynamic leading to that equilibrium provide a rapid detection of deep stall and the implementation of a recovery strategy
Podeur, Vincent. "Modélisation expérimentale et numérique du power take-off d’un bassin houlomoteur." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2022. http://www.theses.fr/2022ENTA0005.
Повний текст джерелаThe present work aims at studying the power take-off of a wave energy converter (WEC). This system is composed of a set of connected tanks. Rubber flaps are installed at tanks inlet and outlet to ensure a one-way flow direction. Thanks to wave induced motions of the supporting platform, sloshing appears inside the WEC tanks which feed a cylindrical basin with a centered drain hole at its bottom. Then, a bathtub vortex flow appears within this tank, where a vertical axis turbine is installed to harvest kinetic energy from the flow. The first phase of this research focuses on studying the steady bathtub flow. To do so, a dedicated experiment is built. Velocity field within the cylindrical basin, with and without the turbine, is studied via Particle Image Velocimetry (PIV). In addition, power production from the turbine and water level inside the tank are measured. These results are used to define starting hypothesis for developing a numerical model of the turbine. The second phase of this research focuses on studying the unsteady bathtub flow. For this purpose, a second experiment is built. This setup provides a more realistic environment, closer to what can be observed with the WEC system. PIV measurements are also used extensively to study the flow with and without the turbine. The last stage of this research focuses on the numerical modelling of the vertical axis turbine. The model is based on the potential flow theory. First, a two-dimensional approach is used to validate the early pieces of the model. Secondly, a three-dimensional approach is adopted to account for more complex flow features. Finally, numerical and experiment results are compared
Srinath, Sricharan. "Prédiction et modélisation d’écoulements turbulents proche de paroi." Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0029/document.
Повний текст джерелаThe aim of the present work is to study a boundary layer subjected to a pressure gradient and to compare it with a zero pressure gradient (ZPG) boundary layer at high Reynolds numbers. Within this framework, focus is laid on the behaviour of large-scale coherent structures. Due to their large streamwise extent, these structures are not easy to extract and characterize using standard measurement techniques. For this reason, specific experimental set-ups using PIV in the streamwise/wall-normal planes was designed to capture the large-scale structures and to gain more insight into the mechanisms governing the dynamics of these flows. The achievements of the present investigation can be divided into two parts. The first part revisits the results obtained on a ZPG turbulent boundary layer by probing the origin of a spectral range in a turbulent boundary layer. To this end, a simple model which can in principle be applied to various wall-bounded turbulent flows is proposed from a new perspective based on the work of Townsend-Perry. The second part focuses on improving the understanding of turbulence under an adverse pressure gradient (APG) by performing a complete flow characterisation of an academic test case on a large scale geometry. Emphasis is laid on the characteristics of the structures (length, scaling, energetic contribution and their wall normal distribution) along with the influence of the APG on the large-scale structures. The analysis is also extended to compare the behaviour of APG with the ZPG case at high Reynolds numbers
Mendes, Rafael. "Comportement rhéologique et modélisation des bruts paraffiniques en écoulement instationnaire." Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1062/document.
Повний текст джерелаTransporting waxy crude oils through long pipelines at low temperatures may be challenging, particularly its flow restart after a pipeline shut-in, due to its viscosity increase. The rheological behavior of a model waxy oil with macroscopic flow properties analogous to waxy crude oils is first analyzed using Magnetic Resonance Imaging velocimetry associated to stress measurements in a Couette geometry. While flowing at constant temperature, major irreversible structure break depending on shear intensity are observed. Thus, the critical apparent shear stress beyond which the material flows depends on the thermal and flow histories of the oil. Next, the rheological behavior of two waxy crude oils is studied using rheometrical tests (creep tests, flow restarts, abrupt changes of shear rate and steady flow) after different flow histories, notably during the cooling process. Then, those experimentally observed trends are modeled. Additionally, a comprehensive study of the yield stress in function of flow and temperature histories is presented. It provides an approach for describing the yield stress field inside the pipeline at the flow restart moment. Finally, the entire rheological model is implemented in the computational code for simulating waxy crude oils flow restart of a real scale pipeline
Ikhennicheu, Maria. "Étude expérimentale de la turbulence dans les zones à forts courants et de son impact sur les hydroliennes." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I055/document.
Повний текст джерелаFrench waters have a strong potential for tidal turbines applications. In these areas of strong currents, intense velocity fluctuations are observed in the water column. They ultimately come from variations in seabed bathymetry and can have a strong impact on tidal turbine energy production and fatigue. In order to understand the turbulent structures generation in the wake of obstacles and to build a data base for future numerical studies, the Alderney Race conditions are reproduced experimentally, in a wave and current tank, in Froude similitude and with a Reynolds number as high as possible. In this study, real bathymetric variations are represented using canonical elements: a cube, a cylinder, an inclined plane or a combination of all three. Cases with bathymetric variations higher than average (obstacle alone) are differentiated from average rugosity cases (obstacles combined). In order to characterize the wake behind these obstacles and to study how turbulence evolve in the water column, PIV and LDV measurements are made for various turbulence rates of the incoming flow. Results show that the cylinder alone produces the most spread out wake. In that case, large scale turbulent structures, rising all the way to the surface, are identified. The development of processing methods and data analysis allows the detection of vortex centres and the determination of their properties. The cylinder wake impact on a tri-bladed horizontal axis turbine behaviour is then studied. Depending on the position of the turbine relative to the obstacle, the turbine can be subject to large amplitude loads due to velocity fluctuations generated by the presence of the obstacle in the flow. Force measurements on the blades and turbine dynamic behaviour characterization allow to quantify those load variations. They depend on the turbulent structures impacting the turbine and the shear in the velocity profile. The results obtained could be exploited for further fatigue analyses on blades or on other tidal turbine components
Danlos, Amélie. "Dynamique des jets contrôlés : Application à l'étude du mélange dans des écoulements de jets annulaires à très grand rapport de diamètres." Phd thesis, Université de Rouen, 2009. http://tel.archives-ouvertes.fr/tel-00649177.
Повний текст джерелаCaudwell, Tobit. "Convection et stratification induites par une paroi chauffante : mesures expérimentales et modélisations." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAU022/document.
Повний текст джерелаThis thesis focuses on the convective flow induced by a heated isotherm wall. A turbulent boundary layer develops along this wall, and resembles to a plume unlike its typical characterics are significantly modified by the boundary condition at the wall. In this study the environment is a closed box in which the lighter fluid continuously accumulates in the upper part, thus producing a temperature stratification in the interior. In order to better understand the dynamics of such a plume as well as its interaction with the ambient fluid, we deploy an approach that is both experimental and theoretical. Concerning the experiments, we developed a technique which combines Particle Image Velocimetry (PIV) with Laser Induced Fluorescence (LIF). This technique allows to simultaneously acquire the velocity and the temperature of the fluid in a plane which covers the entire flow. As concerning the theory, a one-dimensional numerical model is developed. It is based on the entrainment theory by Morton et al (1956) as for the turbulent part of the plume, and it takes into account the initial laminar character of the plume thanks to similarity solutions. The detailed comparisons between this model and the experimental results show the limits of the classical models and the relevance of the introduced improvements. In particular we evaluate the contribution of the laminar part and we highlight that the entrainment coefficient varies as a function of the ambient stratification
Galati, Chiara. "Experimental and numerical study of flow distribution in compact plate heat exchangers." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19928/1/GALATI_Chiara.pdf.
Повний текст джерелаSeguin, Antoine. "De la pénétration en milieu granulaire." Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00727081.
Повний текст джерелаHussein, Yasser. "Analyse de champs de vitesse par FTLE à partir de la méthode des moments : validation théorique et expérimentale." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2016. http://www.theses.fr/2016ESMA0009/document.
Повний текст джерелаWith the development of technology, instantaneous flow fields coming from experiments or numerical simulation are available now. It has been followed by a rise of interest for the Lagrangian analysis of such data. One central tool to analyze the flow fields is the Finite Time Lyapunov Exponent (FTLE). It allows to the identify of the Lagrangian Coherent Structures (LCS) which appear as ridges in the FTLE fields. The LCS are quasi transport bareers and separatte the fluid domain into regions which have different dynamic properties. However, the computation methodology currently used in order to obtain the FTLE requires numerical evalution of a large number of fluid particle trajectories on cartesian or adaptive meshes that are superimposed on the original data grid.In this thesis, we propose a new method for calculating the Finite Time Lyapunov Exponent FTLE fields. For this, we use the method of second-order moments which allows to evaluate over time the dispersion of particles uniformly distributed in a circular or elliptical domain. We call this new scalar field, the M-FTLE field. We validate this approach theoretically, at every point of the fluid domain by comparing FTLE and M-FTLE and also by the comparison of the classic examples (linear velocity field, circular and hyperbolic) and a numerical example (velocity field of double gyre). This method is then applied on experimental measurements of tidal bore velocity fields, obtained within the institute 'Pprime' by using a measurement technique called particle image velocimetry (PIV)
Jessen, Werneck de Almeida Martins Fabio. "Caractérisation des écoulements turbulents à proximité d'une paroi par PIV tomographique." Thesis, Ecole centrale de Lille, 2016. http://www.theses.fr/2016ECLI0011/document.
Повний текст джерелаThe fundamental study of turbulent structures near a wall is of significant importance due to its dominant role in innumerous engineering applications. In turbulent flows, eddies of different scales interact with each other in a complex phenomenon of a continuous self-sustaining process. Although the presence of patterns of coherent motion seem to be responsible for the maintenance of turbulence, the evolution and the interaction of these structures are still not completely understood. To investigate such phenomena, near-wall turbulent flows over a smooth flat plate in a wind tunnel and inside a square water channel were conducted. The present work employed a high-repetition tomographic PIV technique to measure three dimensional, time-resolved velocity fields. The tomo-PIV processing was optimized in order to improve the algorithm performance and the vector fields accuracy. Conditional statistics of coherent structures, namely, low- and high-speed regions, sweeps, ejections and vortices, were computed, providing quantitative characteristics of these structures. The statistical analyses were performed employing a data post-processing code specially developed for the present work. Results showed vortical structures spread all over the flow, nevertheless, concentrated close to low-speed regions and ejections. Results indicated that vortical structures were indirectly correlated with the process of turbulence production, although they were the main responsible for the turbulent energy dissipation
Gaurier, Benoît. "Etude expérimentale des performances d'une hydrolienne, soumise aux effets de la turbulence et de l'intéraction houle-courant." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMLH11.
Повний текст джерелаIn the context of global warming, the extraction of energy by tidal turbines from marine currents must be integrated into the future energetic mix. Being confronted with a difficult marine environment, it is required to know the turbines’ behaviour when they are submitted to realistic solicitations to guarantee an optimal use. In this work, the marine turbine performance is studied when the machine is submitted to a turbulent current or a combined wave-current effect. The physical representation of trials at reduced scale is first described focusing on the incoming flow characterisation and its effects on a turbine model at 1:20 scale. The locationand measurement type of the upstream velocity are discussed to accurately define its performance and its temporal and spectral response. Such parameters are essential in the definition of certification standards for experimental modelling. The bathymetric variation representation enables turbulent flow to be generated. They are mainly characterized by large eddies with a size corresponding to the rotor. The turbine response is determined in a global and local way for many relative turbine locations versus the obstacles. The combined wave and current effects on the turbine behaviour are studied from measurement results carried out in three facilities. Significant differences between the tanks appear and a discussion on their origin is proposed
Brahami, Yacine. "Mélange à scalaire actif dans les écoulements de jets turbulents." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR093.
Повний текст джерелаActive scalar mixing, which modifies the velocity field through variations of either density or viscosity, received much less attention than passive scalars. This thesis aims at unravelling some open questions pertaining to active scalar mixing. Whilst some results point to the facts that mixing occurs faster for i) light jets than for heavy jets, and ii) more viscous fluid released in a less viscous environment. This simple example reveals the necessity of a systematic study of the problem. We focus on two aspects of these very vast questions. I. Variable density round jet. We designed an experimental set-up, which allows measuring both velocity and scalar fields, using simultaneous Stereo Particle Image Velocimetry and Planar Laser Induced Fluorescence. The first question concerns mixing immediately after injection. Therefore, the very near field of the jet was particularly sought. One-point statistics were used to evaluate the large-scale effect of momentum and density variations on the initiation of turbulence. Also, two-point turbulent statistics for velocity and scalar have been appraised. Through this approach, the effects on transition were assessed through scales of turbulent motion. Mixing was also evaluated at the edge of the flow, in the vicinity of the Turbulent/Non-Turbulent Interface. We found additional specificity to variable density mixing, that is inaccessible by averaging on a cylindrical frame of reference. II. Temporally evolving turbulent jet flow with variable viscosity and mass diffusivity. The data consists in Direct Numerical Simulation performed in our group by Dr. M. Gauding. The purpose of these simulations is to study the kinetic energy and scalar dissipation rates in flows with variable momentum and mass diffusivities. We focused on conditional averaging in the vicinity of Turbulent/Non-Turbulent Interface. This data is confronted to one-and-two point transport equations for the momentum and scalar. It is shown that initial gradients of both viscosity and mass diffusivity have an intense and persistent impact on both kinetic energy and scalar dissipation rates, in the vicinity of the Turbulent/Non-Turbulent Interface, albeit a rapidly trend of the jet core towards self-preservation
Germain, Florent. "Fluorescence plane induite par laser appliquée à l'étude d'un écoulement de convection mixte - Caractérisation et simulation." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2015. http://www.theses.fr/2015ESMA0006/document.
Повний текст джерелаNon-intrusive metrology is essential in experimental fluid mechanics experiments. In particular, simultaneous acquisition of instantaneous velocity and temperature fields offers valuable insights in instationnary aerothermal behaviours. However, if instantaneous velocity fields can be acquired quite easily using the Particles Image Velocimetry technic (PIV), instantaneous temperature fields are much more complex to obtain. Plannar Laser Induced Fluorescence (PLIF) is one of the technics allowing such a measurement. The emitted LASER light induces excitation of acetone molecules, the tracer in the studied air flow. Then, the fluorescence following de-excitation, which is temperature-dependant, is recorded. In particular, 2 λ-PLIF uses dual wavelength LASER excitation to remove acetone concentration dependency in the measurement. Yet, depending of the wavelengths, the LASER energy or the temperature range investigated, using 2 λ-PLIF can be difficult due to a very low temperature sensitivity and very dim fluorescence. To solve those issues and improve signal-to-noise ratio, acquired images can be corrected according to different parameters in an interative process. Present work is dedicated to evaluate efficiency of corrected 2 λ-PLIF applied to the study of a mixed convection flow around a heated cylinder in the 20-300 C temperature range. The goal is to obtain aerothermal qualification of the flow thanks to simultaneous 2 λ-PLIF and PIV. In the present work, experimental bench is detailled as well as the calibrating and correcting process of the 2 λ-PLIF. Then, experimental results are discussed and confronted to results from litterature. Finally, a model of the fluorescence and camera-generated noise is discussed and used to generate simulated fluroescence images and determine the impact of all parameters (wavelengths, LASER energy, acetone concentration and camera intensification gain) on the measurement precision and thus enable adequate choice of equipments for next experiments
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.
Повний текст джерелаThis 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)
Betting, Benjamin. "Etudes Expérimentales et lois prédictives des foyers d'incendies." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR054/document.
Повний текст джерелаEach year in France, compartment fires result in more than 88,000 interventions involving more than 15,000 people, including several hundred deaths and serious injuries. Today, during fire compartments, the decision-making of the rescue teams is mainly based on human decisions, as a result of the accumulated experience. However, a perfect knowledge of the situation, its evolution over time and the dangers that may appear is impossible. Therefore, studying the fumes is of major interest. Indeed, smoke remains important to study because it conveys valuable information, especially on the appearance of thermal phenomena feared by firemen. In order to carry out this study, an experimental cell made up of two maritime containers was installed on the site of the Seine-Maritime fire brigade fire training. This platform will produce hot smokes in a configuration called "real fire" thanks to a propane burner. In this study, the smoke dynamics in a large scale experimental setup is analyzed using a non-intrusive measurement technique such as PIV (Particle Image Velocity). All the performed measurements are compared with LES (Large Eddy Simulation) simulations of the experiment using Fire Dynamics Simulator (FDS). The double expertise (numerical / experimental) is essential in this type of study where the experimental data suffer from a lack of resolution (spatial and temporal) but nevertheless represents an important source of information necessary for the validation of the codes
Nguyên, Van Tuê. "Calcul de pression et d'efforts sur un profil en mouvement : application aux systèmes de récupération d'énergie." Thesis, Poitiers, 2017. http://www.theses.fr/2017POIT2263/document.
Повний текст джерелаThe determination of the pressure field in a flow and/or forces on a moving profile from measurements of velocities carried out in the fluid is a current problem that is of interest to many domains of research in fluid mechanics like the energy recovery systems (wind, hydro) or the speed control of hydraulic turbines, etc…In this PhD thesis, we make a contribution to this problem by initially proposing an original method which allows us to approach unsteady velocity fields in the whole of the flow obtained by PIV optical measurements (including the profile) using Legendre's orthogonal polynomial theory. The Navier-Stokes equations then make it possible to obtain polynomial pressure gradients in the whole of the fluid and thus to be able to calculate the pressure field in the flow by using the momentum balance equation in a judiciously chosen reference range, to determine the forces on an oscillating mobile profile. This method is then validated on a fixed profile using numerically simulated data and experimental data.In a second step, from series of flow PIV measurements on a NACA0015 profile subjected to different types of oscillations, we apply the method described above to reconstruct the unsteady pressure fields and to evaluate the instantaneous and average forces on the profile. The study of a certain number of ranges of frequencies and amplitudes makes it possible to compare our results, in order to seek a better efficiency
Beaudet, Laurent. "Étude expérimentale et numérique du décrochage dynamique sur une éolienne à axe vertical de forte solidité." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2271/document.
Повний текст джерелаThe Darrieus wind turbine has entered a period of renewed interest over the last years because it may stand for an alternative solution to produce electricity in urban areas. In particular, high solidity wind turbine can be chosen to take benefit from some of its key properties for use near populated city areas. Conversely, some aerodynamic problems arise. This type of wind turbine operates at low tip speed ratio for which dynamic stall has a very significant role. The goal of this work is to provide valuable data to complement the knowledge of the dynamic stall phenomenon that occurs on a vertical axis wind turbine in order to improve existing numerical models. This study relies on a combined analysis of numerical and experimental results. The numerical simulations are based on a bidimensional unsteady vortex panel method. Effects of viscosity are introduced by adding corrections computed with a semi-empirical dynamic stall model. The experimental work focuses on the dynamics of the shed vortices existing in the vicinity of the rotor as a result of dynamic stall. The set-up consists of a straight-bladed wind turbine tested in a wind tunnel. Unsteady pressure distribution measurements along the chord and velocity fields measurements by particle image velocimetry were carried out. Results indicate how the characteristics of dynamic stall are conditioned by the tip speed ratio. Stall inception delay, magnitude of the dynamic stall vortex effects and its convection velocity were evaluated. Blade/Vortex interaction was analyzed through the observation of the vortical system downstream of the rotor. In addition, a critical review of the suitability of the Leishman-Beddoes model to effectively simulate the effects of dynamic stall was accomplished
Paisant, Jean-Francois. "Modélisation numérique et validation expérimentale de l'hydrodynamique d'une émulsion dans une colonne d'extraction." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066453/document.
Повний текст джерелаIn the core of spent fuel reprocessing operations, the pulsed columns with packing are the liquid-liquid extraction apparati mainly used. The context of economical competiveness and scarce resources, industrials are driven to improve the efficiency of these processes. Pulsed column efficiency is bound to the amount of available exchange surface, which depends on geometrical parameters of the column and the operating conditions. A better design would improve the efficiency. In this aim the knowledge of the interphase slip velocity is necessary. The work presented in this thesis revolves around physical and numerical modelling of the hydrodynamics of the emulsion and its experimental characterization.In this work, a eulerian approach, based on the work of D.Lhuillier, allows to obtain a two-fluid model coupled with an evolution equation of the exchange surface (interfacial area). We use finite elements method to solve this model along with CAST3M software. Numerical simulations have shown the model abilities to correctly reproduce the emulsion behaviour and to obtain the slip velocity.In order to experimentally validate the model, we carried out two types of experimentation. Particles images velocimetry coupled to laser induced fluorescence are involved to obtain velocities of each phases and the dispersed phase volume fraction. We developed a tracking algorithm to obtain the dispersed phase velocity and the hold up. These results, such as velocities and strain rate tensor, have been used in a first validation of the model
Hamdi, Jana. "Reconstruction volumique d’un jet impactant une surface fendue à partir de champs cinématiques obtenus par PIV stéréoscopique." Thesis, La Rochelle, 2017. http://www.theses.fr/2017LAROS027/document.
Повний текст джерелаAir conditioning and ventilation systems are often composed of jets having a configuration of an impinging jet, on their end part. Thus, the blown airflows impact slotted obstacles of different shapes to improve mixing. The conditions of confinement and blowing sometimes cause acoustic incompatibility. The acoustic noises generated are due to a phenomenon of feedback loops resulting of the appearance of self-sustained sounds. The production of sound by a free flow or in interaction with a structure has been the subject of many studies. In the case of an acoustic field and for a flow of low Mach number, Howe's energetic correlation is used to evaluate the acoustic power generated or absorbed by the interactions between the acoustic field and the flow. The calculation of this power requires the knowledge of three parameters : vorticity, velocity and acoustic velocity by analytical methods or by using experimental data. Experimentally, the measurement of the kinematic field, to deduce the vorticity, requires a three-dimensional measurement technique. For this purpose, an experimental platform, using laser velocimetry, has been developed and equipped to generate flows of a plane jet. The kinematic fields of these flows were measured using the PIV technique, with a stereoscopic PIV device. The kinematic fields of thirty parallel planes were measured to study the corresponding velocity fields. Two reconstruction methods have been applied to these plans : the POD and the phase average. The volume is obtained by an interpolation of the reconstructed planes giving access to the three components of the velocity. To validate these low-cost 3D reconstruction methods, they were compared to experimental measurements made by the same experimental setup, under the same conditions, by using the tomographic PIV giving access to the three-dimensional kinematic fields
De, Souza David. "Dynamique de sédimentation de particules." Thesis, Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAE003.
Повний текст джерелаThe dynamics of heavy inertial particles evolving in a fluid are of interest in many fields.They are found both in nature (water droplets in clouds, sediments in rivers and in the oceans, planetary accretion disks) and in human activities and technological applications (fuel drops in combustion chambers, chemical reactors).These systems are complex, their modelling using often strong simplifying hypotheses, and experimental data is still required in their study.A large range of behaviours can be found in such dispersed two-phase flows.This work focuses on two of these.The first is clustering, or the observation that particles accumulate in specific regions and leave others void.The second is settling velocity alteration, as particles have been observed to fall either faster or slower than in a quiescent fluid.These two phenomena are intertwined, and depend on parameters like the size and density of the particles, what the carrier phase is (water or air usually) and whether it is in a quiescent or turbulent state.An experimental device was built in which small (diameters of at most 200 µm) solid particles settle in water.Particles of various densities have been separated by size by sieving.This allows access to a large variety of particle properties.An easy to implement double-measurement technique allowing simultaneous measurements of particle and fluid velocities was developed, providing insight into particle-fluid interactions that was seldomly achieved in previous works.Increases of the settling velocity of particles falling in a quiescent fluid have been observed and could be attributed to the development of a flow that pushes the particles down.Voronoï analysis were also performed, but could not confirm with certainty whether particles formed clusters or not.This work gives interesting data, relevant in the study of particles settling in quiescent fluids in closed spaces.It also provides a reference point for future works where turbulence will be added to the system
Bonnet, Dimitri. "Vélocimétrie par images de particules (PIV) pour le diagnostic d'écoulements dans la boucle d'air automobile." Phd thesis, Université de Franche-Comté, 2012. http://tel.archives-ouvertes.fr/tel-00978193.
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