Tesis sobre el tema "Simulation directe numérique"
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Rueda, Villegas Lucia. "Simulation numérique directe de l'effet Leidenfrost". Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/14177/1/rueda.pdf.
Texto completoVoronetska, Kateryna. "Simulation numérique directe des écoulements à phases dispersées". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14507/document.
Texto completoThe flow of immiscible fluids is a frequent issue in the petroleum industry: hydrocarbon in pipelines, separation process for production, fuel injection in engines, refinery treatment processes, etc.There are two possible approaches to model this type of flow. In the first one, the flow is described macroscopically. In this case, local phenomena (breakage or coalescence of droplets, phase slip, local compaction) are modeled thanks to analytic closure laws or empiric laws. In the second approach, the flow is simulated indirectly on a scale of droplet and we want to describe precisely the interface and the interactions between phases. We propose here to consider the second method to study liquid/liquid dispersed flows and especially the phenomena of breakage or coalescence and collision or distortion of the droplets.Thus, the main purpose of this work was the development of a direct numerical simulation code that is capable to model a liquid-liquid two-phase flow, in order to study in detail the effects of droplets coalescence and breakage. To model a two-phase flow, it is necessary to choose an appropriate interface tracking method and to develop a solver for Navier-Stokes incompressible equations to compute the velocity and pressure values. Also, a coupling method that is able to handle the discontinuous quantities at the interface has to be implemented. Our numerical tool has been validated on numerous academic test cases and applied to study the process of liquid-liquid separation
Le, Martelot Sébastien. "Contribution à la simulation numérique directe de l'ébullition". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4758/document.
Texto completoPart of the researches concerning the Vinci cryogenic engine, created to propel the last part of Ariane 6, the main goal of this thesis is the direct numerical simulation of boiling flows.Simulation this kind of flow requires the modelling and the resolution of the multiple internal physical effects as well as phases interactions. To achieve this goal, we created models and numerical schemes suited to the boiling flows. The method is used on fine meshes in order to be able to resolve the flow structure, essentially at the interface
Zuzio, Davide. "Simulation numérique directe d'écoulements diphasiques avec maillage auto adaptatif". Phd thesis, Ecole nationale superieure de l'aeronautique et de l'espace, 2010. http://tel.archives-ouvertes.fr/tel-00630136.
Texto completoKomiwes, Vincent. "Simulation numérique directe d'écoulements granulaires en présence de fluide". Paris 6, 1999. http://www.theses.fr/1999PA066268.
Texto completoBenjeddou, Saïd. "Simulation numérique directe des gaz fortement chauffés et approximation polytropique". Aix-Marseille 2, 2003. http://www.theses.fr/2003AIX22088.
Texto completoRoblin, Simon. "Etude numérique de l'auto-inflammation des solides par simulation numérique directe : application au polyméthacrylate de méthyle". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2016. http://www.theses.fr/2016ESMA0023/document.
Texto completoFire propagation on the scale of buildings and cities is a major stake. It is conditioned by the ignition of solid fuels in rooms adjacent to the one where the disaster originally takes place. The ignition is so piloted by the initiation of the combustion reaction of the gaseous mixture stemming from the thermal decomposition of the condensed phase induced by heat transfer.Two types of ignition are defined in the literature: piloted-ignition related to the presence of a hot spot and auto-ignition resulting from the thermal runaway within the gas phase. The auto-ignition plays a major role in the context of fire spread between rooms. However, this process has been very little experimentally studied, because of its complexity, and only theoretical analyses were lead concerning the phenomena which take place during solid fuels auto ignition.The aim of the present study is to characterize auto-ignition regimes according to various solid typologies (regarding to thermal and kinetic behaviour) in order to understand better their processes and their occurrence conditions. Thereby, this fine understanding allows to develop global models of fire spread for a deterministic consideration of the fire hazards at urban scale.The brief and local character of the auto-ignition requires the choice of a complete resolution for flows, transfers and chemistry. Thus, the Direct Numerical Simulation (DNS) was selected to capture the phenomena, with the introduction of a fine and non-infinitely fast chemistry of thermal decomposition and combustion
Caudal, Jean. "Simulation numérique du reformage autothermique du méthane". Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-00862538.
Texto completoNoël, Emeline. "Simulation numérique directe d'écoulements à l'aide d'une méthode de frontière immergée". Phd thesis, INSA de Rouen, 2012. http://tel.archives-ouvertes.fr/tel-00845203.
Texto completoHarribey, Thibault. "Simulation numérique directe de la turbulence en présence d'une paroi ablatable". Toulouse, ISAE, 2011. http://www.theses.fr/2011ESAE0010.
Texto completoDuquennoy, Christophe. "Développement d'une approche de simulation numérique directe de l'ébullition en paroi". Toulouse, INPT, 2000. http://www.theses.fr/2000INPT032H.
Texto completoHilka, Martin. "Simulation numérique directe et modélisation de la pollution des flammes turbulentes". Châtenay-Malabry, Ecole centrale de Paris, 1999. http://www.theses.fr/1998ECAP0640.
Texto completoNoël, Emeline. "Simulation numérique directe d’écoulements à l’aide d’une méthode de frontière immergée". Thesis, Rouen, INSA, 2012. http://www.theses.fr/2012ISAM0020/document.
Texto completoSince several years, the research conducted at the CORIA laboratory led to the development of a numerical tool (ARCHER) alllowing direct numerical simulations of two phase flows. In particular, the simulations of high speed liquid jet primary break-up have been strongly investigated. These simulations are able to capture primary break-up phenomena near the nozzle exit where experimental characterisations are difficult to conduct. These simulations need injection conditions tricky to gauge a priori, since they depend on the flow characteristics inside the nozzle. Moreover, some jets are highly sensitive to these injection conditions. Therefore, it becomes necessary to simulate the flow inside the nozzle to better understand this sensitive nature. The objective to simulate the whole atomization system guided the present work dedicated to the use of an immersed boundary method (IBM). Such an approach allows reproducing flows inside nozzles of arbitrary shape while keeping the original cartesian mesh valuable for numerical efficiency and accuracy. As a first step, the implementation of an IBM in ARCHER was carried out and tested on channels, pipes and uniform flows past a circular cylinder. An industrial application focused on the flow inside a triple disk compound injector. This work led to a refined description of the secondary flow origin in the discharge hole. In order to move towards the design of a numerical tool able to simulate the whole injection system, a coupling between IBM and the Ghost Fluid Method (GFM) has been found necessary. This allows accounting for two phase flows inside the nozzle where the dynamics of the triple line has to be considered. The bidimensional developments have been tested on drops released on walls. This version enabled to simulate flows inside channels with different ratios of length over diameter and the flow inside a convergent nozzle. The simultaneous computation of flows inside and outside nozzle has enabled to link the velocity fluctuations of internals flows to the surface setting-up gene-rated on external flows
Solak, Ilkay. "Simulation numérique directe et analyse des grandes échelles d'une couche limite turbulente". Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1I029/document.
Texto completoThis work lies at the intersection of two problems concerning turbulence (i) the description of coherent structures of turbulent boundary layer flow and (ii) the numerical methods for high-performance computing of these flows. The main objectives are to analyze coherent structures and to develop new numerical tools to be used in turbulence research with a special focus on the turbulent boundary layers. A new direct numerical simulation of a turbulent boundary layer flow over a flat plate is conducted with the code Incompact3d. A relationship between attached flow structures and the streamwise energy spectra in a turbulent boundary layer has been established similarly to an earlier experimental study. A novel application of the skeletonization method is proposed to obtain detailed statistics of coherent structures. Statistics of large-scale motions (LSM) and Reynolds Shear Stress quadrant structures are compared. In the second part, a new test-suite is implemented to the in-house incompressible Navier-Stokes solver. Performance of the code is analyzed. The stability problems at high Reynolds numbers are addressed and some solutions are proposed
Solak, Ilkay. "Simulation numérique directe et analyse des grandes échelles d'une couche limite turbulente". Electronic Thesis or Diss., Université de Lille (2018-2021), 2018. http://www.theses.fr/2018LILUI029.
Texto completoThis work lies at the intersection of two problems concerning turbulence (i) the description of coherent structures of turbulent boundary layer flow and (ii) the numerical methods for high-performance computing of these flows. The main objectives are to analyze coherent structures and to develop new numerical tools to be used in turbulence research with a special focus on the turbulent boundary layers. A new direct numerical simulation of a turbulent boundary layer flow over a flat plate is conducted with the code Incompact3d. A relationship between attached flow structures and the streamwise energy spectra in a turbulent boundary layer has been established similarly to an earlier experimental study. A novel application of the skeletonization method is proposed to obtain detailed statistics of coherent structures. Statistics of large-scale motions (LSM) and Reynolds Shear Stress quadrant structures are compared. In the second part, a new test-suite is implemented to the in-house incompressible Navier-Stokes solver. Performance of the code is analyzed. The stability problems at high Reynolds numbers are addressed and some solutions are proposed
Xavier, Thibault. "Simulation numérique directe de l’impact de SLD (Supercooled Large Droplet) sur une paroi". Thesis, Toulouse, ISAE, 2020. http://www.theses.fr/2020ESAE0008.
Texto completoIn-flight icing prevention is a major issue in the aeronautical world, since it's one of the major causes of accidents.When supercooled droplets impact the airfoil, icing accretion occurs and can dramatically deteriorate the aeronauticalperformances or obstruct sensors. In this context, a deep understanding of drop impact phenomenon isneeded to answer the new regulations from certification agencies and at the same time to improve the eficiency ofice protection devices. Using a Direct Numerical Simulation (DNS) tool allows us to provide physical quantitieshard to access by experimental means. However, high-velocity impacts demand the use of precise, conservativeand stable numerical methods, as well as high computational ressources. In this PhD, we make a contribution tothe understanding of drop impact on different targets (dry wall or liquid film) with both low and high impactvelocity. This work has been accompished by developing and using the DNS code DYJEAT based on incompressibleNavier-Stokes equations for two-phase flows. The use of both Level-Set and Volume-of-Fluid methodsallows us to cope with this numerical challenge. First, spreading phenomenon is studied by implementing a lawfor capillary effects at the triple line. Then, the crown formation following the impact on a liquid film is analyzed.Specific methods for post-processing are developed to precisely characterize both geometrical crown topology andsecondary droplets. From the analysis of high-velocity impacts recorded by ONERA lab, we devise and performa series of simulations on configurations barely addressed by now in the litterature. The influence of wettability, incidence angle and ambient pressure on splashing phenomenon are highlighted. This kind of simulation requiresheavily refined mesh surpassing the billion mesh cells. In this high-performance context, calculation practices needto be reworked to eficiently perform simulation and post-processing on supercomputer at a regional or national level
Martinez, Ferrer Pedro José. "Simulation numérique directe dans la combustion turbulente sur une couche de cisaillement". Phd thesis, ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2013. http://tel.archives-ouvertes.fr/tel-00937313.
Texto completoDuret, Benjamin. "Simulation numérique directe des écoulements liquide-gaz avec évaporation : application à l'atomisation". Phd thesis, INSA de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00971810.
Texto completoLardeau, Sylvain. "Simulation numérique directe du contrôle d'écoulements cisaillés libres par injection de fluide". Poitiers, 2001. http://www.theses.fr/2001POIT2328.
Texto completoGeorge, Sijo. "Simulation numérique directe de la transition laminaire turbulent sur un hydrofoil flexible". Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0010.
Texto completoThe laminar to turbulent transition induced vibration over a NACA66 hydrofoil at Re = 450000 is investigated in this thesis. DNS is used to simulate the 3D incompressible boundary layer flow, and it is coupled with a freely pitching hydrofoil. An implicit coupling is developed within the fluid solver Nek5000. A number of cases are performed to validate this method, which lead to study the transition induced vibration. Then, a parametric study consisting of two forced and three free oscillations allowed analyzing the interactions between the vibration and the boundary layer transitional flow. A set of specific non-dimensional parameters are set, which aim at characterize the fluid structure interactions in such flow regime. From the boundary layer flow analysis, it was observed that the spatial location of the transition point is proportional to the amplitude of pitch, velocity, and frequency ratio. The generation of TS waves (the first stage of laminar to turbulent transition) is also influenced by the vibrations. It was also observed that the span wise wavelength of coherent structures (so called “hair-pin” structures” that form downstream of the TS waves) is proportional to the displacement thickness. The spatial advancement of the transition point reduces the amplitude of periodic pressure fluctuations in the transition regime. In addition, the length of the transition region is increased. Finally, a multi-scaled frequency response is observed due to the enhanced interaction between transition and pitch oscillation when the transition and natural frequencies are close to each other. The study suggests that in this case, the fluid structure interaction tends to disturb the spatio-temporal behavior of laminar to turbulent transition. Although it has to be confirmed, this phenomenon has already identified experimentally through measurements performed at the Naval Academy Research Institute (IRENav) in hydrodynamic tunnel for a higher Reynolds number case
Dombard, Jérôme. "Simulation Numérique Directe des sprays dilués anisothermes avec le Formalisme Eulérien Mésoscopique". Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0091/document.
Texto completoThis work addresses the Direct Numerical Simulation of non-isothermal turbulent flows laden with solid particles in the dilute regime. The focus is set on the accurate prediction of heat transfer between phases and of particles dispersion. The dispersed phase is described by an Eulerian approach : the Mesoscopic Eulerian Formalism [41, 123], recently extended to non-isothermal flows [78]. The main objective of this work is to assess the ability of this formalism to accurately account for both dynamic and thermal inertia of particles in turbulent sheared flows. The CFD code used in this work is AVBP. The numerical simulation of dilute sprays with an Eulerian approach calls for specific modelling and raises additional numerical issues. First, the numerical methods implemented in AVBP for two-phase flows [69, 103, 109] were tested and revisited. The objective was to propose an accurate and robust numerical strategy that withstands the steep gradients of particle volume fraction due to preferential concentration [132] with a limited numerical diffusion. These numerical strategies have been tested on a series of test cases of increasing complexity and relevant diagnostics were proposed. In particular, the two-dimensional vortex laden with solid particles was suggested as a simple configuration to illustrate the effect of particle inertia on their concentration profile and to test numerical strategies. An analytical solution was also derived in the limit of small inertia. Moreover, dissipations due to numerics and to physical effects were explicitly extracted and quantified. Eventually, the numerical strategy coupling the highorder centered scheme TTGC with a stabilization technique –the so called artificial viscosity– proved to be the most accurate and robust alternative in AVBP if an adequate set-up is used (i.e. sensors). Then, the issue of the accurate prediction of particle dispersion in configurations with a mean shear was adressed. One of the RUM model (denoted AXISY-C), proposed by Masi [78] and implemented by Sierra [120], was successfully validated in a two-dimensional and a three-dimensional non-isothermal jet laden with solid particles. Contrary to the former RUM models [63, 103], the main statistics of the dispersed phase were recovered at both the center and the edges of the jet. Finally, the impact of the thermal inertia of particles on their temperature statistics has been investigated. The results showed a strong dependency of these statistics to thermal inertia, pinpointing the necessity of the numerical approaches to account for this phenomenon. Therefore, the extension of the MEF to non isothermal conditions, i.e. the RUM heat fluxes, has been implemented in AVBP. The impact of the RUM HF terms on the temperature statistics was evaluated in both configurations of 2D and 3D jets. Eulerian solutions were compared with Lagrangian reference computations carried out by B. Leveugle at CORIA and by E. Masi at IMFT for the 2D and 3D jets, respectively. Results showed a strong positive impact of the RUM HF on the fluctuations of mesoscopic temperature, and to a lesser extent on the mean mesoscopic temperature depending of the configuration. Neglecting the RUM HF leads to erroneous results whereas the Lagrangian statistics are recovered when they are accounted for
Leboissetier, Anthony. "Simulation numérique directe de l'atomisation primaire d'un jet liquide à haute vitesse". Paris 6, 2002. http://www.theses.fr/2002PA066492.
Texto completoKessar, Mouloud. "Simulation numérique directe de la turbulence hélicitaire maximale et modèles LES de la turbulence magnétohydrodynamique". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI042/document.
Texto completoHomogeneous and isotropic turbulence was first formalized by Kolmogorov (1941), through dimensional analysis. He managed to show that the spectral density of kinetic energy, $E(k)$, was following a $k^{-5/3}$ law. This behaviour is known as Kolmogorov's cascade. For many geophysical and astrophysical flow, kinetic helicity plays an important role. For instance, Parker (1955) showed that for conductive fluids such as Sun, kinetic helicity could contribute to amplify the magnetic field. Brissaud {it et al} (1973) tried to show that kinetic helicity could have an influence on the spectral density of kinetic energy. Through dimensional analysis they suggested the existence of a cascade for which the kinetic energy spectra would follow a $k^{-7/3}$ law. In the first part of this thesis we will confirm thanks to Direct Numerical Simulations (DNS) the existence of such an asymptotic limit in $k^{-7/3}$. We will also use helical decomposition to perform a deep analysis of the physics encountered within such flows. In several geophysical and astrophysical fluids, turbulence is very strong, and involves a large range of scales. Despite the strong development of computational resources the last few decades, it remains impossible to simulate this range of scales for realistic configurations. One solution is known as Large Eddy Simulations (LES). While a LES is performed, only the large scales of the flow are resolved, and the interactions between large and small scales are modeled. Several turbulence models have been developed for LES of turbulence. Nevertheless, the limitations of these models are not always well known for magnetohydrodynamic (MHD) turbulence, i.e for conductive fluids that can be encoutered in geophysics and astrophysics. In the second part of this thesis we will evaluate the functional performances (see Sagaut (2002)) of these models for several flow configurations involving turbulent dynamo action, i.e when a magnetic field is amplified though the action of a turbulent conductive fluid. In particular we will study the capabilities of LES models to reproduce energy exchanges between large and small scales. In order to do so, we will perform several DNS, for both non-helical flows (i.e leading to small scale dynamo) and helical flows (i.e leading to large scale dynamo). Thanks to a filtering operation we will compute the exact subgrid-scale transfers and compare them to the predictions given by several models. Finally we will achieve LES using subgrid-scale models and we will compare them to filtered DNS
Campagne, Gaelle. "Simulation numérique directe de l'interaction turbulence/surface libre pour l'analyse du transfert intercomposantes". Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2006. http://tel.archives-ouvertes.fr/tel-00326401.
Texto completoCampagne, Gaëlle. "Simulation numérique directe de l'intéraction turbulence / surface libre pour l'analyse du transfert intercomposantes". Toulouse, INPT, 2006. http://ethesis.inp-toulouse.fr/archive/00000435/.
Texto completoA Direct Numerical Simulation of the interaction between no-shear turbulence and a free-slip surface is performed using a pseudo-spectral method. The originality of the configuration yields in the fact that the turbulence is created by a distant random forcing term localised in the vicinity of a plane parallel to the surface. The flow is therefore statistically steady and the surface layer is continuously fed by turbulent diffusion. The evolutions of the statistical quantities and of Reynolds shear stresses are studied and are used to define the structure of the interaction layer. A new method of analyzing and quantifying the elementary structures, that contribute to the intercomponent energy transfers, is proposed and evaluated. It allows some improvements in the understanding of the mechanisms linked to the influence on the pressure-deformation correlation, in the presence of an impermeable surface
Bruneaux, Gilles. "Etude asymptotique, simulation numérique directe et modélisation de l'intéraction flamme turbulente prémélangée -paroi". Châtenay-Malabry, Ecole centrale de Paris, 1996. http://www.theses.fr/1996ECAP0462.
Texto completoMoon, Hee-Jang. "Modèles de combustion turbulente appliqués à l'autoinflammation. Comparaison avec la simulation numérique directe". Rouen, 1991. http://www.theses.fr/1991ROUES010.
Texto completoTroadec, François. "Simulation numérique directe d'un écoulement supercritique pour validation des approches RANS et LES". Rouen, 2010. http://www.theses.fr/2010ROUES043.
Texto completoThe main aim of this work is to develop tools able to realise numerical simulation of cryogenic flows by proposing tests case based on numerical experiments through the use of Direct Numerical Simulation (DNS). Many problems encountered during experiments are due to experimental conditions (high pressure and very flammable reactives) that impose researchers to consider new numerical ways. Indeed, beyond a given pressure, the distinction between liquid and gaseous phase disappears and molecular interactions can’t be neglected anymore. This affects thermo-physical variables. So, different physical models have been studied and results have been compared to reference data (NIST). Some of them have been introduced in Asphodele solver. This solver is based on a low Mach number formulation. The reference configuration used simulates the destabilization of a jet in supercritical condition. Main aim being to reach conditions present inside the rocket’s combustion chamber and to test low Mach number formulation applied in supercritical flows. Finally, from results extracted from DNS simulation, a priori tests are used to study RANS and LES terms modelisation like the mixture fraction formulation (RANS) and the use of filtered variable in equation of state (LES)
Ould, Salihi Mohamed Lemine. "Couplage de méthodes numériques en simulation directe d'écoulements incompressibles". Phd thesis, Université Joseph Fourier (Grenoble), 1998. http://tel.archives-ouvertes.fr/tel-00004901.
Texto completoHauguel, Raphaël. "Flamme en V turbulente : simulation numérique directe et modélisation de la combustion turbulente prémélangée". Rouen, INSA, 2003. http://www.theses.fr/2003ISAM0007.
Texto completoCastaldi, Stéphane. "Étude de la turbulence cinématiquement homogène isotrope et massiquement inhomogène par simulation numérique directe". Toulouse, INPT, 1999. http://www.theses.fr/1999INPT008H.
Texto completoTroff, Bruno. "Simulation directe d'écoulements externes décollés par résolution numérique des équations de Navier-Stokes tridimenssionnelles". Paris 6, 1991. http://www.theses.fr/1991PA066648.
Texto completoLabit, Benoit. "Transport de chaleur électronique dans un tokamak par simulation numérique directe d'une turbulence de petite échelle". Phd thesis, Université de Provence - Aix-Marseille I, 2002. http://tel.archives-ouvertes.fr/tel-00261562.
Texto completoLa thèse proposée ici cherche à déterminer la pertinence d'un modèle fluide non linéaire, électromagnétique, tridimensionnel, basé sur une instabilité particulière pour décrire les pertes de chaleur par le canal électronique et de déterminer les dépendances du transport turbulent associé en fonction de paramètres adimensionnels, dont β et ρ*. L'instabilité choisie est une instabilité d'échange générée par le gradient de température électronique (Electron Temperature Gradient (ETG) driven turbulence en anglais). Ce modèle non linéaire est construit à partir des équations de Braginskii. Le code de simulation développé est global au sens qu'un flux de chaleur entrant est imposé, laissant les gradients libres d'évoluer.
A partir des simulations non linéaires, nous avons pu mettre en évidence trois caractéristiques principales pour le modèle ETG fluide: le transport de chaleur turbulente est essentiellement électrostatique; les fluctuations de potentiel et de pression forment des structures radialement allongées; le niveau de transport observé est beaucoup plus faible que celui mesuré expérimentalement.
L'étude de la dépendance du transport de chaleur en fonction du rapport de la pression cinétique à la pression magnétique a montré un faible impact de ce paramètre mettant ainsi en défaut la loi empirique d'Ohkawa. En revanche, il a été montré sans ambiguïté le rôle important du rayon de Larmor électronique normalisé dans le tranport de chaleur: le temps de confinement est inversement proportionnel à ce paramètre. Enfin, la faible dépendance du transport de chaleur turbulent en fonction du cisaillement magnétique et de l'inverse du rapport d'aspect a été mise en évidence.
Bien que le niveau de transport observé dans les simulations soit plus faible que celui mesuré expérimentalement, nous avons tenté une confrontation directe avec un choc de Tore Supra. Ce tokamak est particulièrement bien désigné pour étudier les pertes de chaleur électronique. En conservant la plupart des paramètres d'un choc bien référencé de Tore Supra, la simulation non linéaire obtenue donne un seuil en gradient de température proche de la valeur expérimentale. Le niveau de transport observé est plus faible d'un facteur cinquante environ que le transport mesuré. Un paramètre important qui n'a pu être conservé est le rayon de Larmor normalisé.
La limitation en ρ* devra être franchie afin de confirmer ces résultats. Enfin une rigoureuse confrontation avec des simulations girocinétiques permettra de disqualifier ou non l'instabilité ETG pour rendre compte des pertes de chaleur observées.
Mots-clés: fusion thermonucléaire, tokamak, plasma, turbulence ETG, simulations numériques
Fortuné, Véronique. "Etude par simulation numérique directe du rayonnement acoustique de couches de mélange isothermes et anisothermes". Phd thesis, Université de Poitiers, 2000. http://tel.archives-ouvertes.fr/tel-00006902.
Texto completoHammouti, Abdelkader. "Simulation numérique directe en différence finie de l'écoulement d'un fluide incompressible en présence d'interfaces rigides". Phd thesis, Ecole des Ponts ParisTech, 2009. http://pastel.archives-ouvertes.fr/pastel-00511607.
Texto completoGorgoraptis, Eleftherios. "Simulation numérique directe pour la modélisation de la combustion Diesel dans des configurations d’injections multiples". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC111/document.
Texto completoCompression-ignition engines are widelyused, mainly due to their high thermal efficiency andconsequent low CO2 emissions compared to sparkignitionengines. However, this technology has somedisadvantages related to the limited control over autoignitionof the air-fuel mixtures and heat release rate.Hence, in compression-ignition engines at their mostbasic form, the level of combustion noise and emissionsof nitrogen oxides and particulate matter canbecome critical. An effective strategy to tackle theseproblems is to decompose fuel injection into multipleinjection pulses permitting an optimal control of theair-fuel mixture formation and, thus, of the autoignitiondelay and the heat release rate. Multiple injectionstrategies become more and more popular dueto their advantages over conventional single injectioncycles. The physical phenomena involved in suchconfigurations, however, are complex and their modellingremains challenging, especially in the context ofindustrial 3D simulation using the Reynolds-averagedNavier-Stokes (RANS) formalism. The progress ofcompression-ignition applications depends to a greatextent on the capacity of the physical models to predictheat release rate and pollutant emissions. Thelack ofa experimental results at the scale of interestorientated this study towards the use of Direct NumericalSimulation (DNS) providing a model-free insightinto the interaction between turbulent mixing and combustionchemistry. In the framework of this Ph.D. thesis,a DNS database was generated and analysed,covering a range of single and split Diesel injectionrelevantconditions. Then, different turbulent combustionmodels based on tabulated chemistry were evaluatedby comparison with the DNS results. Followingthis analysis, a new modelling approach adapted tomultiple injection configurations was elaborated. Finally,a strategy for the application of the new modellingapproach in 3D RANS was proposed for prospectivemulti-injection compression-ignition engine simulationswith an improved accuracy
Alvinerie, Eric. "Contribution à l'étude des jets anisothermes plans par analyse de stabilité et simulation numérique directe". Poitiers, 1996. http://www.theses.fr/1996POIT2335.
Texto completoLuo, Haining. "Simulation numérique directe pour un écoulement turbulent dans un T-jonction d'un fluide non-Newtonien". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC026/document.
Texto completoFor the simplicity in geometry by comparing it with other mixers in the industry, flows in T-junction configuration have been studied. More specifically, Direct Numerical Simulations is carried out using OpenFOAM on a convergent T-junction configuration with circular and rectangular cross-section. Both Newtonian and non-Newtonian fluids (Bird-Carreau model) are taken into account. Firstly, DNS data is compared to Nguyen’s experimental work on the circular T-junction at regime deflecting [1]. Good agreement between simlation and experiment is achieved. The organization of coherent structures is illustrated in laminar and turbulent for both Newtonian and non-Newtonian cases. Secondly, two flow regimes (deflecting and impinging) are simulated in a rectangular T-junction for the same Newtonian and non-Newtonian fluids. The existence of non-Newtonian coherent structures (e.g. kidney vortex ) is shown. These structures are regarded as essential mixing mechanism of passive scalar mixing. The mixing efficiency is increased in regime impinging compared to regime deflecting. The shifting of the turbulence peak is only observed in regime impinging
Euzenat, Florian. "Simulation numérique directe et analyse des transferts de chaleur dans les lits de particules fixes et mobiles". Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/21358/1/EUZENAT_Florian.pdf.
Texto completoMichel, Antoine. "Simulation du comportement d'ellipsoïdes en écoulement turbulent confiné". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0188.
Texto completoUsing direct numerical simulation (DNS), the dynamics of inertial, non-spherical particles carried by the turbulent flow in a channel has been studied numerically. Under the hypothesis of pointwise particles, modelled as prolate ellipsoids, Lagrangian particles tracking is used to study the influence of the particle aspect ratio and inertia on their interaction with the flow. Direct numerical simulation of the flow allows to obtain an accurate information about the properties of the fluid at the particle position, which are required to compute the hydrodynamic actions that they undergo. The hydrodynamic actions have been computed using two different methods to study the influence of their modelling on the particle dynamics. The first model is based on theoretical formulas which are valid under the assumption that there is a creeping flow motion at the particle scale and are widely used in the literature. The second model relies on correlations, which are valid at moderate values of the particle Reynolds number. Simulations have been carried until the particle distribution reaches a steady state in order to obtain an unbiased comparison of the influence the particle shape and inertia. For both modelling of the hydrodynamic actions, translation velocity statistics do not significantly depend on the particle shape. There are however important quantitative differences between the translation statistics obtained using each model. Angular velocity statistics are strongly influenced by the hydrodynamic actions modelling, everywhere in the channel. These observations about the influence of the modelling remain valid for higher values of the flow Reynolds number. Increasing the value of this parameter nonetheless causes an uniformization of the particle distribution and increases the magnitude of the fluctuations of the velocity and angular velocity of the fluid seen by the particles. These stronger fluctuations modify the preferential orientation of the ellipsoids, regardless of their characteristics and of the model used to compute the hydrodynamic actions. The comparison of the simulation results with experimental data indicates that the model valid under the creeping flow assumption allows to simulate the dynamics of very long and weakly inertial ellipsoids realistically
Marter-Lagrange, Isabelle. "Méthode d'interface immergée pour la simulation directe de l'atomisation primaire". Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0040/document.
Texto completoThe reduction of polluting emissions and improvement of aeronautical engines efficiency depends on the detailed knowledge of the physical phenomena encountered in a combustion chamber. Fuel atomization results from the shearing effect induced by the high velocity airflow generated inside the injector. The Direct Numerical Simulation of interfacial flows allows the simulation of the whole atomization process, while Cartesian structured meshes allows efficient and accurate HPC computations. However, the complexity of atomization comes from a strong interaction between the jet behavior and the injector internal flow, which makes essential to simulate the whole injector system. As that is impossible on Cartesian structured grids, the main objective of this thesis is to develop an Immersed Interface Method (IIM) allowing the inclusion of solid objects in the computational domain, independently of the mesh. The incompressible two-phases Navier-Stokes equations are solved using a projection algorithm with the CLSVOF method, conservative in mass and momentum. The solid presence is taken into account using the IIM. The proposed IIM has been applied to the numerical simulation of sheared liquid sheets corresponding to an ONERA experimental configuration and allows a better prediction of the flapping frequencies of the liquid sheet
Thiam, Elhadji Ibrahima. "Modélisation et simulation numérique directe des transferts de chaleur dans les écoulements fortement chargés en particules". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30086.
Texto completoTo better characterize and understand heat transfer in fixed and fluidized beds of particles, numerical studies have been carried out in this work. Based on fully Particle Resolved Numerical Simulation (PR-DNS) local and instantaneous informations have been obtained at microscopic scale and further analyzed at macroscopic scale by means of volume and time averages. The first step consisted in a thorough validation of the numerical code on academic configurations (conduction and convection around a single particle). Then, an analysis in arrays of random fixed particles was carried out for several particle volume fractions, Reynolds and Prandtl numbers. From this analysis, the solid-fluid heat transfer was investigated at macroscopic scale and a closure model for the pseudo-turbulent heat flux was proposed. Finally, fluidized bed simulations were performed. These simulations needed a preliminary numerical study in order to select appropriate numerical parameters for accurately reproducing the fluidization with a moderate computational cost. Furthermore, a comparative study of the heat transfer in fixed and fluidized beds was carried out. The entire study aimed at improving the understanding of the heat transfer in particulate flows and dense regimes, in order to provide information for the modeling at macroscopic scale
Piot, Estelle. "Simulation numérique directe et analyse de stabilité de couches limites laminaires en présence de micro-rugosités". Toulouse, ISAE, 2008. http://www.theses.fr/2008ESAE0018.
Texto completoRambaud, Patrick. "Contribution à l'étude du comportement de particules solides en écoulement turbulent confiné par simulation numérique directe". Nancy 1, 2001. http://www.theses.fr/2001NAN10204.
Texto completoThe behavior of solid particles in a turbulent gas channel flow is studied by direct numerical simulation. A mixed Eulerian and Lagrangian formulation allowed us to deal with the dispersion of small solid particles through the computation of the integral time scales of the turbulence seen by the solid particles on their trajectories. Those integral times are compared with the ones estimated thank to a semi-empirical correlation established with direct numerical simulation in isotropic and homogeneous turbulence. The comparison shows the impossibility to use this correlation to predict the streamwise dispersion. Beside this dispersion study, the turbulence modulation due to solid particles is shown. The forces taken into account on the particles in all the simulation are at least the non-linear drag and the Saffman's lift both corrected for near wall effect and using a fully three-dimensional Hermitian interpolation
Ritz, Jean-Benoît. "Modélisation numérique des écoulements fluide-particules : définition d'un modèle de simulation directe, application à la sédimentation". Bordeaux 1, 1997. http://www.theses.fr/1997BOR10560.
Texto completoLabit, Benoît. "Transport de chaleur électronique dans un tokamak par simulation numérique directe d'une turbulence de petite échelle". Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX11052.
Texto completoMartínez, Ferrer Pedro José. "Étude par simulation numérique de l'auto-allumage en écoulement turbulent cisaillé supersonique". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2013. http://www.theses.fr/2013ESMA0018.
Texto completoThis study is devoted to the analysis of supersonic reactive shear flows and, in particular,compressible mixing layers that can develop inside the ramjet and scramjet engines.Appropriate numerical methods have been implemented and tested to achieve the developmentof a massively parallel numerical solver, called CREAMS (compressible reactivemulti-species solver). This tool was designed to conduct high-precision numerical simulations(direct numerical simulations or DNS) of such flows. Particular attention waspaid to the description of the molecular transport terms and chemical source terms toconsider the most accurate physical description of reactive gas mixtures at high velocity,in which the chemical and mixing time scales, corresponding to the smallest scalesof the flow, are susceptible to be of the same order of magnitude. Simulations of twoandthree-dimensional, inert and reactive, mixing layers confirm the importance of theeffects associated with compressibility and rate of heat release. The results obtained differin some points from other simulations which introduced simplifying assumptions such astemporal development, use of a global chemistry or a simplified description of the moleculartransport terms. Nevertheless, they reproduce some trends already observed in severalexperimental studies conducted under similar conditions
Bouchard, Jonathan. "Caractérisation d'un régénérateur ferromagnétique poreux utilisé en réfrigération magnétique". Thèse, Université de Sherbrooke, 2008. http://savoirs.usherbrooke.ca/handle/11143/1835.
Texto completoIssa, Heitham. "Simulation numérique d'un bassin à houle par la résolution directe des équations de Navier-Stokes : application : étude de l'écoulement autour d'un obstacle immergé". Poitiers, 2006. http://www.theses.fr/2006POIT2266.
Texto completoThis thesis deals with a numerical method based on the simulation of unsteady and laminar two dimensional free-surface incompressible flows. Navier-Stokes equations are discretized by finite differences. The pressure is obtained by solving a Poisson equation dealing with a provisional velocity field. The Poisson equation is solved by a finite volume method. An interface capturing method (surface tracking) is used to evaluate the free-surface elevation. The incident regular waves are generated in the left end of the tank by a numerical wave maker. Numerical damping method with stretched mesh is used for wave absorption at the outlet boundary. Concerning the flow around a submerged body, the grid around the obstacle was refined by the Adaptive Mesh Method called AMR
Deutsch, Emmanuel. "Dispersion de particules dans une turbulence homogène isotrope stationnaire calculée par simulation numérique directe des grandes échelles". Ecully, Ecole centrale de Lyon, 1992. http://bibli.ec-lyon.fr/exl-doc/TH_T1454_edeutsch.pdf.
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