Teses / dissertações sobre o tema "Dynamique d’écoulement"
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Kourtzanidis, Konstantinos. "Modélisation numérique d’actionneurs plasma pour le contrôle d’écoulement". Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0040/document.
Texto completo da fonteAs aerodynamic flow control still remains one of the top subjects of research in the aerospace scientific world, new ways to perform such a control are being constantly studied. Plasma actuators based on momentum or energy addition in the flow, have been proven capable of positively modifying the flow aerodynamic features. Nevertheless, the development and optimization of such actuators, require further understanding of the basic multi-scale physics involved. In this thesis, we are interested in the numerical modeling of plasma flow control actuators. Three types of plasma actuators are considered: Microwave Plasma Discharges (MPD), the Dielectric Barrier Discharge (DBD) and the Plasma Synthetic Jet (PSJ). Concerning MPDs, a novel implicit approach has been developed which with have enabled three-dimensional simulations in time domain in reduced CPU time. The microwave breakdown and evolution of the plasma due to the electromagnetic waves has been studied numerically, demonstrating the three-dimensional nature of such discharges. Coupling of the EM-plasma model with an Euler based solver accounting for real gas effects, have revealed the plasma modification due to the intense gas heating. For the PSJ actuator, the numerical solver consists of three coupled numerical models and the obtained results of its operation offer important information of its performance and its limits. The DBD actuator has been numerically studied using 2 different solvers (based on the same physical model). Both solvers were capable to give quite accurate estimations of the induced force due to the plasma and various parametric studies have been conducted. These studies offer new perspectives in the understanding and the optimization of plasma actuators for flow control purposes
Joubert, Gilles. "Simulation numérique du contrôle de décrochage dynamique d'un profil en oscillation de tangage". Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2273/document.
Texto completo da fonteThe helicopter flight envelope is limited by dynamic stall, which can be reduced by flow control actuation. Numerous studies are dedicated to the alleviation of dynamic stall, however no actuator has ever been used on real rotor configuration. A new deployable Vortex Generator-type actuator called DVG has been designed by the ONERA and proved its efficiency over pitch-oscillating dynamic stall control of an OA209 airfoil. However, the control effect must be in-depth analyzed before further application. Therefore, the present works aims at reproducing the dynamic stall control through numerical simulations,in order to investigate the physics involved. After a first part dedicated to the literature review of dynamic stall control and Vortex Generators, a second part considered the validation and investigation of the static stall control. DVG-induced secondary flow has been characterized by its vortex interactions, which reduce the control efficiency because of the DVG thickness. This analysis made a preliminary modeling of the DVG possible. In a third part, validation and investigation of the dynamic stall control have been performed, and the actuation showed strong similarities with the static case. Eventually, Proper Orthogonal Decomposition of the flow brought evidence of Dynamic Stall Vortex mode distortion thanks to DVG presence. This work validates the numerical simulation methodology, lets hope possible improvement of the actuator design and allows further numerical simulations of dynamic stall control over real helicopter blades
Saker, Assia. "Étude critique de quelques techniques expérimentales d’évaluation de la coulabilité des poudres". Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0314.
Texto completo da fonteIn industrial sectors, such as chemical, pharmaceutical or food industries, poor flowability of powders is often the causes of process malfunction. Poor flowability can lead to the blocking of powders in a silo, dosing and filling problems, or even bad quality on final product. To ensure proper process operation, it is therefore necessary and essential to evaluate the flowability of powders used. For this purpose, several experimental techniques such as angle of repose devices, shear cells or powder packing devices can be used. Flowability indices can then be defined in order to classify the powders according to the flow quality. Experimental tests have been carried out on several types of powders and the first results have shown that the transition from one technique to another can modify or even reverse the classification of the powder flowability. Indeed, according to the techniques studied, powders are subjected to different mechanical stresses and therefore the choice of the technique must be adapted to the real case of study. In this work, we were particularly interested to the evaluation of powders flowability from compaction devices. The work carried out has shown that the dynamic parameters (amplitude and frequency of taps) greatly influence the classification of powders flowability. From an energy approach, it has been shown that the evaluation of the flowability from Hausner ratio can be given by a compaction technique only if it achieves a value of energy required to obtain a maximal compaction of the particles. Finally, an implementation study of flowability evaluation techniques was carried out in the field of formulation by focusing on the quantitative evaluation of the influence of a glidant
Saker, Assia. "Étude critique de quelques techniques expérimentales d’évaluation de la coulabilité des poudres". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0314.
Texto completo da fonteIn industrial sectors, such as chemical, pharmaceutical or food industries, poor flowability of powders is often the causes of process malfunction. Poor flowability can lead to the blocking of powders in a silo, dosing and filling problems, or even bad quality on final product. To ensure proper process operation, it is therefore necessary and essential to evaluate the flowability of powders used. For this purpose, several experimental techniques such as angle of repose devices, shear cells or powder packing devices can be used. Flowability indices can then be defined in order to classify the powders according to the flow quality. Experimental tests have been carried out on several types of powders and the first results have shown that the transition from one technique to another can modify or even reverse the classification of the powder flowability. Indeed, according to the techniques studied, powders are subjected to different mechanical stresses and therefore the choice of the technique must be adapted to the real case of study. In this work, we were particularly interested to the evaluation of powders flowability from compaction devices. The work carried out has shown that the dynamic parameters (amplitude and frequency of taps) greatly influence the classification of powders flowability. From an energy approach, it has been shown that the evaluation of the flowability from Hausner ratio can be given by a compaction technique only if it achieves a value of energy required to obtain a maximal compaction of the particles. Finally, an implementation study of flowability evaluation techniques was carried out in the field of formulation by focusing on the quantitative evaluation of the influence of a glidant
Szmigiel, Mathieu. "Etude du flux de soubassement sur la dynamique du sillage d'un corps non profilé à culot droit : Application du contrôle actif pour la réduction de traînée de véhicule industriel". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC016/document.
Texto completo da fonteThis PhD thesis was realized in the scope of a collaboration with Renault Trucks and the LMFA in view of an evaluation of the relevance of active flow control for the drag reduction industrial vehicle. The two main objectives of this experimental work are to analyze the impact of the underbody flow on the wake dynamics and to study a flow control strategy combining inclined flaps (located on the upper and lateral edges of the rear base) with pulsed jet actuators for reducing the aerodynamic drag of a square-back bluff body. The wake development for several underbody velocities ranging from 10% to more than 80% of the free-stream velocity is studied on a simplified truck model at scale 1 :43. Rear base pressure measurements lead to the identification of four flow classes associated with different wake structures highlighted by 2D-3C PIV measurements. The wake of the first flow class obtained for very low underbody velocities looks like that of the wake of a 3D backward facing step. For higher underbody velocities, the underbody flow is separated from the ground impaging either the rear base or the upper shear layer triggering Kelvin-Helmoltz instabilities for this last case. Finally, the fourth class is characterized by a wake comparable to that of the Ahmed body. The implementation of inclined flaps at the rear base increases the base pressure for all classes. This increase is mainly due to the vectoring effect of the flow. An active control system is integrated to a 1 :8 scale model geometrically identical to that of the 1 :43 scale model with flaps. Two upper flap angles are tested to have (i) a natural flow attached to the flap and (ii) a natural flow detached from the flap. In comparison to the case without active flow control, drag reductions are obtained only for a specific range of actuation frequencies only in case (ii). These gains are associated with the reattachment of the flow on the flap. Finally, the robustness of the pressure gains is successfully tested in crosswind conditions
Laurendeau, François. "Analyse expérimentale et modélisation numérique d’un actionneur plasma de type jet synthétique". Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0023/document.
Texto completo da fonteNowadays, many studies are conducted in order to decrease greenhouse gases and noiseemissions from aircrafts. Active aerodynamic flow control is a way considered to meet thesechallenges. Among developed technologies of control, plasma actuators offer several advantages,including compactness, easy implementation and fast response. This thesis is devotedto the study of a plasma synthetic jet actuator which comes in the form of a small cavityinserted in wall and connected to the environment through a nozzle. An electrical arc isgenerated in the cavity, resulting in an increase of the cavity air pressure. Consequently,a jet is produced at the nozzle exhaust that can interact with the external flow. After thisejection phase, an aspiration phase naturally occurs, allowing the process to be repeatedat a frequency that can reach several kilohertz. This thesis aims at building a numericalmodel able to reproduce these physical phenomena. To do so, a Large Eddy Simulationis performed. The action of the plasma arc is taken into account through source terms inthe energy equation. In particular, these source terms are calculated using the assumptionof local thermodynamic equilibrium in the plasma. In addition, the heating of the actuatormaterials is simulated when it is operated at high frequency. The results from the numericalmodel are compared with velocity measurements, carried out when the actuator works ina quiescent environment and when it interacts with a boundary layer
Orgogozo, Laurent. "Transport de soluté biologiquement actif en milieu poreux incluant une phase biofilm : de la modélisation numérique aux perspectives expérimentales". Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL091N/document.
Texto completo da fonteModeling transport in porous media of organic chemical solute in presence of a bacterial population growing as biofilms is an important area of research for environmental applications, for example for remediation of groundwater contaminated by organic pollutants (biosparging, bio-barriers …). Biofilms, which are composed of bacteria and extracellular organic substances, grow on the pore walls of the porous medium. Bacteria degrade the organic solute by their metabolism and thus may contribute to pollution decrease. Bio-reactive transport of an organic solute in a porous medium including a biofilm phase is a strongly multi-scale (from the bacteria scale to the heterogeneity scale of the aquifer) and coupled (involving hydrodynamic, physicochemical and biochemical phenomena) process. The organic solute is transported by convection and diffusion in the fluid phase and diffuses into the biofilm phase, where it is degraded by bacterial metabolism. The goal of this work is to develop macroscopic models of bio-reactive transport at the Darcy-scale through volume averaging based on the data available at pore-scale. In the general case, the macroscopic system obtained by averaging pore-scale equations is a two coupled equations system (one equation for each phase), called two-equation model. By considering the relation between averaged concentration in the fluid phase and averaged concentration in the biofilm phase, several regimes of transport can be found which allow simplifying this system into a one equation system. The local mass equilibrium assumption leads to such a simplified model. When an equilibrium relationship between phases cannot be considered, a one equation model may though be developed if the biodegration rate is limited by external mass transfer or by the kinetics of bacterial metabolism. The use of these models implies the numerical solving of closure problems, in order to set up the values of the macroscopic transport parameters (dispersion tensor, interfacial flux …). Computations of these effective coefficients have been performed in different situations of mass transport in porous medium in order to study their behaviour. The results of these models have then been compared with direct simulations performed on a simplified geometry representative of a two-dimensional porous medium including a biofilm phase. Based on these comparisons, the validity domain of this model has been identified in terms of hydrodynamic and biochemical conditions of transport (i.e. the Péclet number and the Damköhler number). The set up of an experimental model of transport in a porous media including a biofilm phase has also been started, in order to make experimental validations of the previously developed numerical models and to build up an additional tool to study the considered phenomena
Szulga, Natacha. "Étude expérimentale et numérique du contrôle de transition de couche limite par actionneurs à plasma froid surfacique". Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0032/document.
Texto completo da fonteThe boundary layer transition from a laminar to a turbulent state increases thewall friction drag. Particularly on future aircrafts, one way of reducing fuel consumption,and answering both an environmental and economic issue, consists in delaying the transitionfarther downstream. In this context, the aim of this work is to characterize the impactof Dielectric Barrier discharge (DBD) plasma actuators on the boundary layer transition.When powered with an alternative high voltage, these active actuators produce apulsed body force which is tangential to the wall and, under some conditions, enablesto modify the boundary layer mean velocity profiles to delay the transition. Under otherconditions, the unsteady body force amplifies modal instabilities (Tollmien-Schlichtingwaves) may destabilize the boundary layers, leading to a promoted transition. A first experimentenabled to highlight this competition between the stabilizing mean effect andthe destabilizing unsteady effect by measuring respectively a transition delay and a transitionpromotion. A numerical study based on local stability analyses wass conducted inparallel and showed that a wide frequency range of TS waves is damped by the mean bodyforce, which explains the transition delay. A second experiment, focusing on the mean effect,enabled to show the influence of the actuator position and the cumulative effect ofseveral actuators on the transition delay
Hardy, Pierrick. "Etude et qualification aérothermodynamique et électrique d'un actionneur plasma de type jet". Thesis, Toulouse, ISAE, 2012. http://www.theses.fr/2012ESAE0014/document.
Texto completo da fonteImprovement of aerodynamics and environmental performances is a major issue for terrestrial and aeronautical industry.For fulfilling increasing demand, one of the answers is flow control. To achieve flow control, high performance actuators are needed. An innovative technique called Plasma Synthetic Jet actuator consists on applying an electrical discharge in asmall cavity. Plasma is created and increases gas temperature and pressure which results on the creation of a micro-jet through cavity opening.The PhD objectives are to develop the PSJ actuator, to describe actuator mechanisms and to apply it for controlling noise of a high subsonic jet. The first part of the study consists on defining flow control needs and on developing a PSJ actuator prototype. Then,actuator performances are characterised using electrical measurements of the discharge and using aerodynamic measurements. These measurements show that an electrical model of the discharge is needed. Based on the Braginskii model, a simple model is carried out and is applied to the actuator. Efficiency of the PSJ is deduced.The modified Braginskii model is then coupled with an URANS model to achieve frequency modelling of the actuator. Results match aerodynamics measurements .PSJ actuators are applied for controlling jet noise in a second part of the study. Schlieren visualisations are used to show micro-jet interaction with the main jet. Acoustic measurements are then performed and show that the PSJ is a goodactuator to control high subsonic jet noise
Ott, Célestin. "Caractérisation dynamique d'actionneurs fluidiques, et identification expérimentale des mécanismes dynamiques d'interaction jet - couche limite induits". Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2020. http://www.theses.fr/2020UPHF0001.
Texto completo da fonteActive flow control research field has high application potential, particularly in the transportation industry, where improving performance while reducing energy consumption represents major economic and environmental challenges. In this context, one of the objectives is to optimize control solutions to ensure a favorable global energy balance. In this thesis, we propose to tackle the question of the actuator choice (conventionally done by trial-and-error) by sharpening the understanding of the dynamic interaction between the actuator and the external flow. To do this, we analyzed the dynamic interaction between a turbulent boundary layer and four types of actuators commonly used in flow control : continuous, pulsed, synthetic and sweeping jet actuators. Thus, a three-dimensional reconstruction methodology based on local time-resolved velocity measurements is developed, which enabled to restore the flow dynamics. This methodology is based on two approaches : one, involving conditional processing, and the other, involving neural networks. These methods enabled the characterization of the intrinsic dynamic of the flow induced by the actuators, as well as the dynamic of their interactions with a turbulent boundary layer. Thanks to these characterizations, the physical phenomena involved were highlighted, as well as the control mechanisms associated with them. These results can be used in future flow control studies to optimize the choice of fluid actuators, based on the configuration and the control objective
Darmet, Natacha. "Prise en compte du risque de propagation de l'emballement thermique dans le développement des modules de batteries. Approche expérimentale tenant compte de la génération de gaz". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI024.
Texto completo da fonteLithium-ion batteries are playing a prominent role in the energy transition, particularly in terms of storage and transportation. The analysis of failure modes reveals that despite of a low probability, the battery self heating has consequences that requires mitigation. Studying the phenomena that lead to the propagation from a cell’s thermal runaway to neighboring cells is essential. The key parameters involved in the thermal runaway propagation for a battery module are evaluated in details in this thesis. Different approaches based on a plurality of characterization methods are proposed. Still, some mechanisms need further developments through specific measures at each stage of the phenomenon.When incidents occur, the cell’s materials react by producing gas, which mechanically affects the cell casing. An experimental device has been developed to measure the internal pressure of the cell, allowing an operando monitoring of this gas generation. The correlation of this measurement with the casing deformations also confirms the significant impact of electrode swelling on the casing’s mechanical strength.At a critical temperature, the lithium-ion cell initiates thermal runaway, which leads to the ejection of materials (gas, flame, particles) at high temperature. Pressure sensors and fast cameras at different spectra were used to analyze the jet dynamics, from its genesis in the cell to its ejection.Heat transfers then occur between the ejecta and surrounding cells, which can results in a thermal runaway propagation. Calorimetry was used to characterize the first cell in order to predict its thermal exchanges in different configurations. Then, based on the knowledge of this energy release and the jet dynamics, a calculation of the emitted heat flow is proposed. The X-rays observations of the active material during the thermal runaway propagation revealed that degradation kinetics and gas generation are linked. It also stresses the importance of trigger cell particles in the thermal propagation risks.Lastly, the thermal runaway propagation between rebuilt charged all-solid-states batteries cells were evaluated experimentally, for the first time. This research has demonstrated that the propagation is feasible with these new battery technologies. The study must be conducted further
Srinath, Sricharan. "Prédiction et modélisation d’écoulements turbulents proche de paroi". Electronic Thesis or Diss., Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0029.
Texto completo da fonteThe 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
Tchekiken, Chahinez. "Modélisation et simulations numériques d’écoulements compressibles dans des micro-conduites planes". Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1109/document.
Texto completo da fonteThese phenomena are rarely taken into account all at once, at least one of them is neglected and often without justification. Our approach is to get as close as possible to reality by taking into account all the phenomena that appear at once and then to study the effect of the phenomena most often overlooked. First, the study is conducted using a commercial code for solving the conservation equations by the finite volume method. Validations were performed for problems ranging from the simplest (incompressible, non-slip flow) to the more complex (compressible, slip flow). This study highlighted the problems associated with simulations when the flows Peclet numbers are less than unity (Pe <1). In this case, the inverse diffusion effects are dominant and the use of extensions at the upstream becomes unavoidable. In addition, compressibility effects were identified; they have resulted in expansions of the gas near the exit of the pipe (acceleration + cooling). Finally, comparisons were made with analytical solutions of compressible slip flows assumed isothermal by imposing small variations of pressure. We showed that these solutions remain valid even if the pressure variations are important because the detents are located only near the exit of the pipe. In this case, they do not affect the properties of the flow. Further works were carried out using an in-house computer code, previously developed and validated in the laboratory for flows with large scales and for which slipping limits conditions have been added so that it can properly resolve slip flows. In view of its accuracy and performances in terms of CPU-time, the code allowed us to achieve a parametric study on a wide range of input and output pressures, so as to sweep all runoff from few to very compressible and few to very slip flow. The results were first presented for quasi-isothermal flow, which subsequently were compared to analytical solutions to test these ones on a wider range of pressure. Finally, the results were made for heated flows. Correlations have been obtained for a complete model using a statistical based software and design of experiments. Comparisons to simplified models were performed to assess the inaccuracies linked to the omission of terms often overlooked in the literature
Mendes, Rafael. "Comportement rhéologique et modélisation des bruts paraffiniques en écoulement instationnaire". Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1062/document.
Texto completo da fonteTransporting 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
Benjelloun, Saad. "Quelques problèmes d’écoulements multi-fluide : analyse mathématique, modélisation numérique et simulation". Thesis, Cachan, Ecole normale supérieure, 2012. http://www.theses.fr/2012DENS0074/document.
Texto completo da fonteThis thesis contains three independent parts.The first part presents a proof of existence of weak global solutions to a Vlasov-incompressible-Navier-Stokes system with variable density. This system is obtained formally from a classical Vlasov-incompressible-Navier-Stokes model with fragmentation for which only two values for the particules radii are considered: a radius r1 for non fragmented particules and a radius r2<
Kuidjo, Kuidjo Emmanuel Vianney. "Towards a predictive model to reproduce flow regime transitions in gas-liquid flows with Neptune CFD : from a dispersed to a separated regime". Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0456.
Texto completo da fonteIn nuclear reactors, several regimes of gas-liquid flows may occur with some transitions between them. The main challenges associated with simulating these transitions in 3D CFD codes are associated with deformable interfaces of different sizes, accounting for coalescence and breakup interactions between gas structures and developing flow regime independent closure relations. This work aims at modelling and simulating the hydrodynamics of adiabatic gas-liquid flows thanks to a three-field two-fluid model in Neptune CFD. In a first step, a model with one continuous liquid field and two dispersed gas fields for small and large bubbles is used to simulate cap and churn flows with a void fraction up to 0.5 and a focus is put on the interfacial area prediction. In a second step, the second dispersed field is replaced by a hybrid continuous/dispersed field representing both large bubbles and continuous gas regions. The model is validated on several flow regimes in large diameter pipes and in confined rectangular channels
Mai, Ton Hoang. "Etudes dynamique et thermique d’écoulements d'air dans une cavité de grand rapport d'allongement en régime in-stationnaire". Lyon, INSA, 1990. http://www.theses.fr/1990ISAL0062.
Texto completo da fonte[In our present work we develop detailed numerical soltwares of the thermal and dynamic behaviour of an thermal instillation wall used to recover power with a counter flow heat exchanger integrated between the extracted and renewed air flow of one building. The first part consists of a theoretical study in in-stationary regime when the system is submitted to a sudden step air flow variation and the energetic gain brought by the exchanger presence. Aeraulics and thermal effects are taken into account in the wall model. Real scale apparatus is modified to obtain a rigours control of the aeraulics and thermal parameters permitting experimentations for the validation of theoretical results. This study leads to air flows modelling of an open vertical cavity weak ventilated with a large aspect ratio. All of these results permit at first to envisage the running mode of the system and secondly to better encircle convection heat transfer phenomenon at fluid-wall interface. In the second part, we study the thermal and energetic performances of this exchange wall integrated in a single zone building. Then we compute of the energy savings brought up by the wall and we compare its energetic gain in relation to other "dynamic" insulation systems (parieto-dynamic, parieto + Heat pump. . . )]
Marcou, Olivier. "Modélisation et contrôle d’écoulements à surface libre par la méthode de Boltzmann sur réseau". Perpignan, 2010. http://www.theses.fr/2010PERP1001.
Texto completo da fonteThis PhD work considers the general problem of modelling and simulation of complex systems and deals with the domain of control and management of water resources. We propose here an original approach based on Lattice Boltzmann models (LB) for modelling free surface flows in irrigation canals, usually described with the non-linear shallow water equations. We adapted a bi-fluid model and studied the boundary conditions which allow to reproduce the geometry of a free-surface irrigation canal. Methods for estimating the desired hydraulic quantities were developed. We studied the behavior of submerged underflow gates, and we show that the model is able to spontaneously and correctly describe how the gates function in quite different situations. Validations were realized by comparing results from simulations and experimentations performed on a laboratory micro-canal facility. We also introduced sedimentation phenomena in the model and studied the influence of a sedimentation deposit on the flow. Comparisons between experimental and simulation results were also performed and converged
Srinath, Sricharan. "Prédiction et modélisation d’écoulements turbulents proche de paroi". Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0029/document.
Texto completo da fonteThe 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
Kaiser, Eurika. "Low-dimensional modeling and control of shear flows using cluster analysis". Thesis, Poitiers, 2015. http://www.theses.fr/2015POIT2295.
Texto completo da fonteA cluster-based reduced-order modeling strategy is developed for the unsupervised identification of nonlinear flow mechanisms and precursors to desirable or undesirable events. The proposed approach assumes a probabilistic viewpoint taking advantage of the linearity of the evolution equation for the probability while including nonlinear actuation dynamics.The framework is applied to the Lorenz attractor, numerical data of the spatially evolving mixing layer, the three-dimensional turbulent wake of a bluf body, of a train, and experimental data of a combustion engine.For these examples, CROM has been shown to identify quasi-attractors such as the two shedding regimes of the mixing layer or the bimodal states of the Ahmed body; main transition processes between those quasiattractors are characterized by branching regions or flipper cluster; desirable phase space regions and possible actuation mechanisms areindicated by analysis of cluster features like drag and lift forces which can be further exploited for control purposes.In particular, a CROM-based feedback control is applied to a separating flow over a smooth ramp to examine whether the recirculation area can be diminished compared to the best open-loop periodic excitation by turning the actuation on or of depending on the applicable cluster. The CROMbased control is compared to the complete set of control laws defined byall possible combinations of 'on' and 'of' for the given set of clusters.While the recirculation area cannot be further decreased compared to the best open-loop forcing, a similar size can be achieved for 28% (CROMbased control) or 81% (one particular control law) savings in the control input energy
Feingesicht, Maxime. "Contrôle non linéaire actif d’écoulements turbulents décollés : Théorie et expérimentations". Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0024/document.
Texto completo da fonteFlow control is a strongly growing field aiming at modifying fluid flows using actuators and control algorithms. An important part of flow control is the control of flow separation as boundary layer separation increases drag and therefore energy losses and fuel consumption. This thesis focuses on developing control algorithms for flow reattachment using pulsed jets actuators. The first part of this work develops a model identification technique based on experimental data. The models are derived from physical and control theory considerations. They provide a good fit to the data while remaining simple and using few coefficients. The second part of this work uses this models in order to design two different control algorithms : the first one is an optimal feedforward control while the second one is a robust feedback control. The control algorithms have been applied on several experimental setups (LML, ONERA, LAMIH) and their properties have been experimentally tested. The tests were conducted using a simple Arduino Uno for the measurements and computation of the control, showing that the developed method is easy to apply and requires very few computational resources
Lallement, Julien. "Modélisation et simulation numérique d’écoulements de films minces avec effet de mouillage partiel". Thesis, Toulouse, ISAE, 2019. http://www.theses.fr/2019ESAE0005/document.
Texto completo da fonteThe ice accretion on surfaces encountered in aeronautics (wings, nacelle lips, sensors)is considered as a major risk for aviation safety. The consequences observed are the degradationof the aerodynamic performances that can lead to the aircraft stall, disturbancesin the engines that can lead to flame out or clogging of the sensors. That is why aircraftmanufacturers are developing thermal protection systems against icing. The wateraccumulated on the surfaces thus remains in the liquid state and forms a thin film. Thedynamic properties (thickness, velocity and spreading) and thermal properties (temperature,evaporation rate) of the film in the presence of a sheared air flow make it possible apotential refreezing of the water film on unprotected surfaces (”runback ice” phenomena).Since flight or wind tunnel tests are generally expensive and difficult to set up, numericalsimulation has become an effective and complementary tool to design these systems. Themain purpose of this thesis is to develop a model integrated in a numerical tool to predictthe transport of liquid water on a surface which might take the form of a film, a rivulet ora droplet. An integral approach based on a shallow water type model is adopted. It makesit possible to describe the macroscopic dynamics of a three-dimensional liquid film onrealistic configurations and within reasonable computing times compared to a full Navier-Stokes computation. An extended formulation is proposed, it corresponds to a second orderdifferential system and thus allows to use arbitrary surface meshes. Contrary to modelsavailable in the literature, the one proposed in this manuscript has the advantage of takinginto account capillary and wetting phenomena without validity limit in term of staticcontact angle. An energy conservation equation ensuring the thermodynamic consistencyof the calculated solutions is derived from the extended model governing fluid dynamics.A Finite Volume discretization of the system is proposed. Numerical simulations validatethe model for both static and dynamic academical wetting configurations. The transitionof a continuous film into rivulets is also simulated
Chaligné, Sébastien. "Contrôle du sillage d'un corps non profilé : application expérimentale à une maquette simplifiée de véhicule industriel". Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00995837.
Texto completo da fontePitakarnnop, Jeerasak. "Analyse expérimentale et simulation numérique d’écoulements raréfiés de gaz simples et de mélanges gazeux dans les microcanaux". Toulouse, INSA, 2009. http://eprint.insa-toulouse.fr/archive/00000300/.
Texto completo da fonteThis thesis focuses on analytical, numerical and experimental investigations on moderate rarefied gas flows through microchannels, for which the local equilibrium assumption is no longer valid. A specific experimental setup has been developed for measuring gas microflowrates under controlled temperature and pressure conditions. The experimental flowrate data of monatomic gases (Ar and He) and their mixtures through rectangular microchannels are compared in the slip flow regime with data from continuum models associated with second-order boundary conditions, and in the transition regime with data from the linearized Boltzmann equation. The collision term of the Boltzmann equation is given by the BGK model for monatomic gases and by the McCormack model for gas mixtures. It is clearly pointed out that the validity of the continuum approach is limited to average Knudsen numbers less than 0. 1. On the other hand, the kinetic models show an excellent agreement with the experimental data for monatomic gases in the whole considered Knudsen range, assuming diffuse reflection at the wall. However, for the mixtures in higher rarefied regimes, deviations occur; further investigations will be required for more definitive conclusions
Nicolas, François. "Reconstruction de champs instantanés de masse volumique par BOS 3D. Applications à l’étude d’écoulements complexes en grande soufflerie". Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0003/document.
Texto completo da fonteThis PhD work is part of the development of advanced metrological tools for fluid dynamics, especially for wind tunnel applications. 3D Background Oriented Schlieren (BOS), which has been developed at ONERA, is a line-of-sight technique which takes advantage of light rays deviation through an inhomogenous index media to measure density. It consisted in comparing a reference image of a textured background with the image of the background with the flow in presence. Image correlation can then be used to compute light rays deviations. Performing such acquisition from multiple view points, allows to reconstruct the corresponding density field, by solving an inverse problem. In order to pursue the technique development, we first elaborate a systematic processing chain and improved the robustness of the reconstruction algorithm. After validating our method on synthetic data, we applied it on a 3DBOS bench equipped with 12 cameras. Thereafter, the technique has been set up for the first time in a wind tunnel environment, on a subsonic hot jet configuration. During this test campaign, the technique has been validated via thermocouples measurements.Moreover, 3DBOS and stereo-PIV coupled acquisitions have been performed. Thereafter, a demonstration in industrial wind tunnel has been performed in ONERA S1MA facility. Compressible flows issues encountered during those tests lead us to finer analysis high density gradient flows. A 3DBOS test bench has been built in laboratory in order to optimize underexpanded jet measurements. On this specific configuration, very good agreements have bee obtained in comparison with literature and with a DES simulation. This study has allowed the extension of 3DBOS application domain to compressible flows and it has demonstrated its use in a wind tunnel environment. The quality of the results highlights the technique potential for flows physical investigation
Bardy, Gaétan. "Intégration de modèles approchés pour mieux transmettre l’impact des incertitudes statiques sur les courbes de réponse des simulateurs d’écoulements". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0253/document.
Texto completo da fonteAlthough it is common to use many different numerical models for the static description of underground reservoirs and their associated uncertainties, for fluid flow uncertainties through these reservoirs only few dynamic simulations can be used due to performance reasons. The objective of this thesis’ work is to better transmit the impact of static uncertainties on flow simulator’s responses without increasing computation time, using approximated models (proxies). Research has been undertaken in 2 directions: - Implementation of new proxies based on Fast Marching in order to better approach fluid propagation behavior in a reservoir using only a few parameters. This allows to obtain response curves close to those provided by the flow simulator in a very short period of time - Set up a mathematical minimization’s procedure in order to predict flow simulator’s response curves using an analytical model and distances between proxy responses computed on every model. The methods developed during this PhD have been applied on two different real cases in order to validate them with industry data. Results have shown that our new proxy improve the quality of the information about fluid behavior compared to the available proxy even though ours can still be improved. We also highlight that our minimization procedure better assesses dynamic uncertainties if the proxy used is reliable enough
Hennicker, Julian. "Discrétisation gradient de modèles d’écoulements à dimensions hybrides dans les milieux poreux fracturés". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4057/document.
Texto completo da fonteThis thesis investigates the modelling of Darcy flow through fractured porous media and its discretization on general polyhedral meshes. We follow the approach of hybrid dimensional models, invoking a complex network of planar fractures. The models account for matrix-fracture interactions and fractures acting either as drains or as barriers, i.e. we have to deal with pressure discontinuities at matrix-fracture interfaces. In the case of two phase flow, we present two models, which permit to treat gravity dominated flow as well as discontinuous capillary pressure at the material interfaces. The numerical analysis is performed in the general framework of the Gradient Discretisation Method, which is extended to the models under consideration. Two families of schemes namely the Vertex Approximate Gradient scheme (VAG) and the Hybrid Finite Volume scheme (HFV) are detailed and shown to fit in the gradient scheme framework, which yields, in particular, convergence. For single phase flow, we obtain convergence of order 1 via density results. For two phase flow, the existence of a solution is obtained as a byproduct of the convergence analysis. Several test cases are presented. For single phase flow, we study the convergence on different types of meshes for a family of solutions. For two phase flow, we compare the hybrid-dimensional models to the reference equidimensional model, in which fractures have the same dimension as the matrix. This does not only provide quantitative evidence about computational gain, but also leads to deep insight about the quality of the proposed reduced models
Mackaya, Térence. "Etude numérique et expérimentale d’écoulements de fluides à seuil en milieux poreux : contribution au développement d’une méthode innovante de porosimétrie". Thesis, Paris, ENSAM, 2019. http://www.theses.fr/2019ENAM0054.
Texto completo da fonteIn order to characterize porous samples, mercury injection porosmetry (MIP) is still one of the mostly used technique, but also probably one of the mostly critized due to the toxicity of this fluid. Among possible alternatives to MIP, yield stress fluids porosimetry (YSM) has the advantages to be non-toxic and cheap. Starting from flow-rate/pressure gradient Q(∇P) experimental data, the inversion process in YSM allows to determine a pore-size distribution (PSD) of the studied porous sample which, up to this day, was always idealized as a bundle of parallel capillaries with circular cross-sections. Moreover, during all the previous works on YSM, for simplicity reasons, the slip of the fluid against the pore walls was neglected. In this work, this phenomenon very caracteristic of the flow of complex fluids is taken into account in the inversion process through a mechanism involving a slipping layer.In addition, during this work, the influence of the non-circularity of the pores cross-sections on the PSDs obtained by YSM has been investigated. New YSM experimental data acquired on both samples of sintered silicate and Bentheimer sandstones have been processed by incorporating these features of slip and non-circular pore cross sections. The results show that these features strongly influence the obtained PSDs, and therefore open new doors for the future of YSM
Darny, Thibault. "Etude de la production des espèces réactives de l’oxygène et de l’azote par décharge Plasma Gun à pression atmosphérique pour des applications biomédicales". Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2086/document.
Texto completo da fonteOver the past ten years, the cold atmospheric pressure plasma jets (CAPPJ) became useful devices for biomedical applications. Their relatively simple design and use, combine with their ability to produce reactive species (NO, OH, O, …), led to a rapid research growth in this field. A lot of studies have been devoted to quantitative diagnostics development for the reactive species production measurements in the plasma plume. However, it is difficult to compare one jet with another because of the huge variety of discharge geometries, electric power supplies or operating conditions. This thesis deals with the study of the CAPPJ developed in GREMI, the Plasma Gun (helium feeded, microsecond voltage pulse). We have studied discharge mechanisms which strongly impact the reactive species production in near target biomedical application conditions. This study is divided in three parts : the study of helium flow modifications induced by the plasma (strioscopy visualization); the study of plasma propagation inside dielectric capillary (experimental and numerical study of fast plasma propagation dynamic and electric field evolution for helium-nitrogen mixtures); the study of conductive target-plasma interaction (space and time resolved measurements inside the capillary and the plasma plume of helium metastable production, correlated with electric field evolution). The conductive target contact concerns any in vivo biomedical treatments. CAPPJ in front of such a conductive target leads to fundamentally different discharge mechanisms compare to the free jet case
Prothin, Sebastien. "Interaction entre un tourbillon et une couche limite Application au contrôle d’écoulement". Thesis, 2010. http://oatao.univ-toulouse.fr/9876/1/Prothin_9876.pdf.
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