Tesi sul tema "Poudres – Dynamique des fluides"
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Marikh, Khadija. "Mélange des poudres en continu : dynamique et modélisation". Vandoeuvre-les-Nancy, INPL, 2003. http://www.theses.fr/2003INPL093N.
Jiménez, Garavito Maria Camila. "Influence of flowability improvement of powders on its dust generation capacity". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0138.
Granular matter is ubiquitous in daily life and industry. After water, it is the second most frequently manipulated material form. However, even today, handling grains entails some sloppy and/or dangerous operations, due to poor flowability and dust emission. Although flow additives such as silica nanoparticles (S-NP) are commonly used to improve flow behaviour, dust emission is often overlooked from a formulation perspective. Therefore, this thesis aims to develop a methodology for powder product conception that preserves good flowability while minimizing dust emissions, leading to safer and less complicated processes for workers and facilities. To achieve this goal, experimental tests were carried out to improve the flowability of four industrial powders using S-NP with varying surface coverage (SC). The results indicated that S-NP main action mechanism on flow improvement is related to surface modification, which was quantified by surface energy measurements. However, dustiness results showed that increasing flowability resulted in increased dust emissions. Moreover, the propensity of a powder to release dust appears to be related to its adhesive interaction with S-NP, which was associated with surface energy and specific surface modifications. Based on the experimental characterization of the samples' flowability, dustiness, and physicochemical properties, a model was developed that predicts dustiness from flowability measurements. Furthermore, the specific surface of the samples was found to be an influential parameter for both end-use properties, allowing their prediction. These results allow the development of three formulation methodologies that could reduce S-NP use while still granting a performing and safer product conception transposable to different industries. By optimizing the formulation of powders, industries can improve their processes' safety and efficiency, reducing the potential risks and costs associated with handling granular materials. This thesis provides a useful approach to developing a systematic methodology for powder product conception that can be implemented in various industrial applications
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.
In 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
Enferad, Shirin. "Compactage et vieillissement des poudres : influence de la formulation". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0214.
This study is conducted in the framework of the “PowderReg” project, funded by the European program Interreg VA GR within the priority axis 4 “Strengthen the competitiveness and the attractiveness of the Grande Région Groβregion”. Understanding the link between microscopic organization and powders flow behavior is a major step forward in establishing criteria for optimizing their transport, storage and processing properties. Whereby, better understating of powder flow behavior saves the industries from huge economic loss. Therefore, it is essential to evaluate their flowability. This work consists in experimentally studying the influence of powder formulation, particle size, as well as influence of environmental condition such as humidity on flow behaviors of powders. Five types of formulations have been analyzed: control glass bead has been used as reference powder and three types of surface formulations consisting of hydrophilic, hydrophobic and lactose coating as well as agglomerated lactose powder have been prepared. First, influence of two different sizes 100 and 500 µm on flow behavior of powders has been analyzed. Then, the powders flow behavior has been considered with different experimental equipements: FT4, Granutools and Rheometer Discover HR3. Including different techniques, such as shear cell, compressibility, rotating angle of repose, etc. The objective was to figure out the behavior of powders under different processing conditions. The, results reported that the transition from one technique to another can modify the classification of the powder flowability. Since the powders were experiencing different mechanical stresses. At the last part of this thesis, we observed the impressive influence of humidity after 80 % on flow behavior of two different size of control glass beads (40 and 100 µm). Small diameter glass bead showed lower flowability which is due to the more surface contacts of these particles. Furthermore, the comparison of flow behavior of control and hydrophobic glass beads with 100 µm size at high shear rate reported the same flowability for both samples. While at low shear rate measurements by vibrational rheology revealed higher flowability in control glass bead. The flowability of control glass bead decreased dramatically after 80 % of humid control, however hydrophobic formulated glass bead kept its flow behavior like as before with very low sensitivity to humidity. Finally, influence of addition of small quantity of water on flow behavior of control glass bead has been investigated
Ansart, Renaud Dodds John Ryck Alain de. "Émission de poussières lors de la manipulation de poudre interaction entre les particules en mouvement et l'air ambiant /". Toulouse : INP Toulouse, 2008. http://ethesis.inp-toulouse.fr/archive/00000594.
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.
In 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
Madian, Ahmed. "Étude de l’influence des caractéristiques physiques des poudres UO2 sur leurs propriétés rhéologiques". Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2461/document.
The nuclear fuel for the fourth generation sodium-cooled fast neutron reactors presents characteristics which differentiate it from that used in Pressurized Water Reactors: a homogeneous structure (U,Pu)O2, an annular geometry and a high content of PuO2. The manufacturing process of the fuel pellets starts with the realization of a UO2/PuO2 mixture by co-grinding followed by forming by pressing. However, the UO2/PuO2 mixture does not exhibit the suitable properties for a reproducible filling of annular press moulds. An intermediate operation, between the co-grinding and the shaping, is necessary to facilitate the filling of the moulds. To direct the choice of this operation, a separate effects study was carried out on UO2 granules, considered as representative of the crushed powder in a first approach. The investigated target physical characteristics are the powder size distribution and morphology. Therefore, mixtures of granules of various sizes were characterized to evaluate the influence of the quantity of fines (particles with a size lower than 100 μm) on the rheological properties. In parallel an intercomparison study between shear cells of different volumes and types (Schulze cell and FT4) was carried out in order to have a good compromise between the quantity of powder used and the quality of the results. A first objective was to determine the proportion of fines acceptable. Then to evaluate the effect of the surface quality of the granules, an operation of spheroidization was carried out. This resulted in modifying the granules roughness. It has been shown that both the fines ratio and the surface roughness are influential parameters that make it possible to modify the rheological properties. In particular within the framework of this study, the presence of fines with a size lower than 100 μm does not seem to have a negative impact on incipient flow up to about 10 w%. On the contrary, other properties such as permeability are sensitive to the fines amount, even below 10 w%. A spheroidization stage enables to improve incipient flow properties of the powder even above 10 w% of fines. These results lead to two possible action modes, which are the grain size selection and the spheroidization, the latter being the most adapted for our application
Boumehdi, Leïla. "Hydrodynamique et transfert thermique d’un contre-courant gaz-solides à travers un faisceau tubulaire". Compiègne, 1985. http://www.theses.fr/1985COMPI191.
Li, Ming. "Study of the FT4 powder rheometer : comparison of the test methods and optimization of the protocols". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2327/document.
This research has been dedicated to evaluate the reliability of the FT4 and to improve the current tests for a better and convenient powder characterization. Firstly, efforts are made to explore the differences between the compaction test provided by the FT4 and the traditional tapped density measurement. Results indicate that the FT4 compaction test has good repetability but it may underestimate powder compressibility. This method can be optimized by improving its initialization procedure to give consistent results as the tapped density measurement. Secondly, the shear tests provided by the FT4 are evaluated by comparing with the methodologies provided by Schulze Ring Shear Tester and Evolution Powder Tester. This comparison indicates that the FT4 shear cell test may underestimate powder strength, especially when a cohesive powder sample is measured, which may cause blockage when using the FT4 method to design a silo. To overcome this shortage, the dimensions of the shear accessories should be optimized. Most importantly, a new characterization technique has been developed. ln this method, powder materials present periodic motions and the cycle time of the periodic flow can be linked to the powder flow properties. This method has very good capability to identify and classify powder flow properties under low stress conditions
Ansart, Renaud. "Émission de poussières lors de la manipulation de poudre : interaction entre les particules en mouvement et l'air ambiant". Toulouse, INPT, 2007. http://ethesis.inp-toulouse.fr/archive/00000594/.
In all cases where powders are handled there is the risk of particles becoming dispersed in the atmosphere leading to suspension in air and eventually deposits on surfaces. Suspension in air means loss of product and more seriously risks to health when operators come into contact with powders by ingestion, or inhalation. Thiscan lead to health problems such as lung cancer or even poisoning if the powders are toxic. This work has been carried out to an experimental set up characterising the mechanisms of dust emission from a falling stream of powders. The aim of this thesis is to design and build an experimental set-up to study the mechanisms by which particles become suspened in air from a stream of particles falling from a silo. The characteristics of the falling stream are observed and measured by optical methods involving, PIV, image analysis and laser diffraction particle size analysis. Mass balances on solids and induced air are determined and compared with a numerical model
Pietraccini, Matteo. "Mechanisms involved in the fast combustion of organic powders : application to dust explosions". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0290.
The industry's risk associated with dust explosions is commonly accepted as high by the scientific community, and it must be reduced to a minimum to improve working conditions. However, the lack of knowledge of the phenomena involved, combined with a scarce general awareness of numerous industrial realities, transforms the dust explosions into profoundly dangerous accidental scenarios. Powder manipulation is a fundamental brick of contemporary industrial reality, and no shortcut can be chosen to bypass it. For this reason, dust explosions are merged with a large variety of processes and need to be studied and well understood. In the second half of the XX century, an energetic transition destabilised the fossil energy sector, painting it greener and greener. As a result, lignocellulosic biomass was and still is one of the most popular worldwide bioenergy sources. Moreover, its enormous versatility and significant technological progress made it possible to start the competition with fossil fuels. The development of the bioenergy sector and the dust explosion are the two actors of this work. Therefore, organic dust explosions were chosen as a study subject, comprehended and characterised to contribute to the scientific knowledge of these phenomena. They can be treated as transient, turbulent, particle-laden systems, which makes them complex and far from being straightforward to understand. Several physicochemical phenomena are involved in the global one. First, a dispersion step is unavoidable in a dust explosion. In this phase, the powder's features may change and strongly impact its behaviour. Second, particle-to-particle interactions are responsible for agglomeration and deagglomeration in the dust cloud thus formed. Again, it can modify the system's characteristics, influencing its thermal comportment. Cohesive forces may lead to strong aggregation of the particles, which has notably a mark on the particle heating time scale. A large selection of organic powders was tested, and their tendency to agglomerate in a dust cloud was quantified. Third, a fundamental brick of organic powder explosions is the pyrolysis step, which can be seen as a devolatilisation responsible for creating a flammable atmosphere within the dust cloud. It is often the rate-limiting step of the global process, and it needs thus to be well analysed. Then, the potential synergy between the gaseous and solid phases can lead to a reactive system different from the sum of the two. Some new phenomena might be generated from this. For instance, radiative heat transfers are major players in the flame propagation phase, strongly dependent on the dust concentration and its optical properties. To conclude, willing to develop an original method to determine the laminar flame speed of organic powders, three apparatuses were selected and compared. The benefits and drawbacks of each were listed and used as choosing criteria
Pessey, Vincent. "Elaboration de poudres inorganiques nanostructurées en milieux fluides supercritiques". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2000. http://tel.archives-ouvertes.fr/tel-00003497.
Marcos, Daniel. "Développement de MOULes INNOVants à haute conductivité thermique pour l’injection de matières plastiques fabriquées par Selective Laser Melting (SLM/LBM)". Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM080.
The aim of this thesis is to propose materials adapted to the needs of a mold cavity for plastic injection, manufactured layer by layer by "Selective Laser Melting" (SLM). The production of high productivity tools requires the design of multi-cavity molds, with high heat dissipation and wear resistance to resist the injection of aggressive polymers with highglass transition and glass fiber reinforced. These molds must be able to with stand high rates and binding thermal cycles. The solution exposed in this thesis is to work on the fabrication by SLM of materials with high thermal conductivity and high hardness. At first, a commercial material partially meeting industrial demand has been proposed. It is a low alloy steel (42CrMo4). A characterization of the powder from a gas atomization was undertaken and its layering characteristics were evaluated. The experiences, of melting it with a laser, have identified a set of viable parameters, allowing the construction of parts with satisfactory metallurgical quality. The development of a suitable heat treatment completes the studyof this steel. The last part of this thesis consist in a proposition of a "design" of powder for the fabrication by SLM of MetalMatrix Composites, with WC base, fulfilling the industrial specifications. However, this study remains exploratory and focused on the identification of metallurgical mechanisms (reactions, changes in solid / liquid and liquid/ vapor states, etc.), thermo-capillarity phenomena and matter transport by gas convection
Jaffal, Basma. "Dynamique des fluides de grade deux". Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00640385.
Mourtada, Basma. "Dynamique des fluides de grade deux". Paris 11, 2010. http://www.theses.fr/2010PA112284.
This thesis is devoted to the study of the second grade fluid system. When the material coefficient dollar\alpha dollar is small, these equations can be considered as a singular perturbation of the Navier-Stokes equations since they involve a third order derivative term. Ln the first part, we consider the equations of a rotating incompressible non-Newtonian fluid flow of grade two in a three dimensional torus. We obtain two different results of global existence of strong solutions. Ln the first case, we consider an arbitrary coefficient dollar\alpha dollar and we suppose that the third components of the vertical average of the initial data and of the forcing term are small compared to the horizontal components. Ln the second case, we consider a forcing term of arbitrary size and large initial data but we need to restrict the size of dollar\alpha dollar. Ln both cases, we show that the system of a rotating second grade fluid converges to a limit system composed of a linear system and a second grade fluid system with two variables and three components. The global existence of solutions of this limit system with three components plays a big role in the proof. Ln the second part, we study the large time behavior of solutions of the second grade fluid system in the space dollar\mathbb{R}Λ2dollar. Using scaling variables and performing energy estimates in weighted Sobolev spaces, we prove that the solutions of the second grade fluid equations converge to the Oseen vortex, if the initial data are small enough. We also give an estimate of the rate of convergence. The last part of this thesis concerns the study of the comparaison of the dynamics of the second grade fluid system with the ones of the Navier-Stokes equations, in the two-dimensional case. We show that, if dollar z_0 dollar is an hyperbolic equilibrium point of the Navier-Stokes equations, the second grade fluid system has a unique equilibrium point dollar z_ {\alpha}dollar in a neighborhood of dollar z_0 dollar , if dollar\alpha dollar is small enough. Next, we construct the local unstable manifold of dollar z_ {\alpha}dollar and we compare it to the local unstable manifold of dollar z_0 dollar
Pachón-Morales, John Alexander. "Torrefaction and grinding of lignocellulosic biomass for its thermochemical valorization : influence of pretreatment conditions on powder flow properties". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC051.
Gasification of lignocellulosic biomass for production of second-generation biofuels is a promising technology to meet renewable energy needs. However, feeding and handling problems related to the poor flowability of milled biomass considerably hinder the industrial implementation of Biomass-to-Liquid processes. Torrefaction as pretreatment step, in addition to improving energy density of biomass, also affects the properties of the milled particles (namely size and shape) that significantly influence flow behavior. The evaluation of biomass flow characteristics under different flow conditions is essential to design efficient and trouble-free handling solutions.The aim of this work is to assess the effect of the torrefaction and grinding conditions on the biomass flow behavior. A first part consists of an experimental study in which the flow properties of samples torrefied under different intensities were obtained using a ring shear tester. Flowability is correlated to the intensity of torrefaction, as measured by the global mass loss, for two different wood species. Particle shape seems to be the predominant parameter influencing flowability of powders in a consolidated state. Characterization of non-consolidated flowability through avalanching analysis using an in-house rotating drum was also conducted. Correlations between particle characteristics and flow behavior are thus established.The modelling of biomass flow using the Discrete Element Method (DEM) constitutes a second major part of this research. Challenging aspects of biomass particle modeling are their submillimetric size, low density, elongated shape and cohesive behavior. A material DEM model is implemented using a simplified (multisphere) upscaled representation of particle shape, along with a cohesive contact model. A systematic calibration procedure results in an optimal set of DEM parameters. The experimental shear stress evolution and yield locus can then be realistically reproduced. The avalanching behavior of the powders is also well captured by simulations, both qualitatively and quantitatively. These results highlight the potential of DEM simulations to investigate the effect of particle characteristics, which are driven by torrefaction and grinding conditions, on the flow behavior of powdered biomass
Lamoine, Jacques. "Dynamique d'un vortex étiré". Paris 7, 2005. http://www.theses.fr/2005PA077218.
This work is about the experimental analysis of a stretched vortex. A vortex is generated thanks to a setup made by PMVH laboratory. This setup can undirectly control the size and and vortidty of the vortex. Vortex dynamics is analysed by using particle image velocimetry with three components of speed. An ‘homemaid’ algorythm is using for detecting vortex's core on every instant velocity field. It helps us to extract relevant datas from noisy instant velocity fields. The analysis of those datas, coupled with observations, leads us to a more accurate understarding of the influence of external conditions on stretched vortex dynamics
Géraud, Baudouin. "Mouillage et dynamique confinée de fluides complexes". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10170.
Complex fluids such as gels, pastes or emulsions have a wide range of applications, both in everyday life and in the industry. Among them, Yield Stress Fluids (YSF) behave either as solids or as non-Newtonian fluids depending on the shear stress applied. These features are modeled by phenomenological laws ( such as the Herschel-Bulkley one ) although their origins are still poorly understood. In this thesis, we focus on the issue of small lengthscales where the structure and interfacial phenomena play predominant roles in the flows. This experimental work was essentially carried out on carbopol, a polymer microgel and a model YSF. The study mainly focuses on three points : – The rheological and structural characterization of the samples. The emphasis is put on the influence of the preparation protocol on the microgel properties. – The case of confined flows of complex fluids. This work highlights the existence of nonlocal effects at the micrometer scales, involving a characteristic length, interpreted in the frame of the fluidity model. – Capillary ascents of complex fluids, involving millimeter scales. This work suggests an extension of Jurin’s law to the case of YSFs. It is shown that this simple experiment allows to measure the surface tension and some rheological parameters of complex fluids such as the yield stress and the Herschel-Bulkley exponent
Deville, Eric. "DYNAMIQUE DES PRISMES OROGÉNIQUES, LE RÔLE DES FLUIDES". Habilitation à diriger des recherches, Université Montpellier II - Sciences et Techniques du Languedoc, 2011. http://tel.archives-ouvertes.fr/tel-00751962.
Funfschilling, Denis. "Dynamique de bulles dans des fluides rhéologiquement complexes". Vandoeuvre-les-Nancy, INPL, 1999. http://docnum.univ-lorraine.fr/public/INPL_T_1999_FUNFSCHILLING_D.pdf.
Makhlof, Hasan. "Dynamique des Fluides Relativistes : Théorie et Approximation Numérique". Paris 6, 2012. http://www.theses.fr/2012PA066523.
Salvert, Marie Adolphe François de. "Étude sur le mouvement permanent des fluides". Paris : Bibliothèque universitaire Pierre et Marie Curie (BUPMC), 2009. http://jubil.upmc.fr/sdx/pl/toc.xsp?id=TH_000284_001&fmt=upmc&idtoc=TH_000284_001-pleadetoc&base=fa.
Agullo, Olivier. "Dynamique des tourbillons et statistique des vortex ponctuels". Aix-Marseille 1, 1997. http://www.theses.fr/1997AIX11067.
Thomas, Thierry. "Contribution à la compréhension des phénomènes physiques et métallurgiques intervenant pendant la consolidation dynamique de poudre". Paris, ENMP, 1992. http://www.theses.fr/1992ENMP0359.
Rivoalen, Elie. "Étude numérique et expérimentale de tourbillons de sillage proches d'une surface libre". Le Havre, 1994. http://www.theses.fr/1994LEHA0007.
Mathieu, Vincent. "Contribution à l'étude de la dynamique d'étalement de fluides newtoniens". Vandoeuvre-les-Nancy, INPL, 2002. http://www.theses.fr/2002INPL020N.
Coulaud, Olivier. "Dynamique de systèmes d'équations non-newtoniens". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00872805.
Sous, Damien. "Dynamique tourbillonnaire en milieu peu profond". Bordeaux 1, 2003. http://www.theses.fr/2003BOR12758.
The shallow water flows are found in lowland rivers, coastal areas, lakes, and stratified atmospheric and oceanic flows. A proper knowledge of shallow flows and their transport capacities is of great importance for predicting the flow in and morphology of riverbeds and coastal zones, for the analysis of natural and anthropogenic parameters(heat, dissolved and suspended solids, biological species) and for weather forecasting. The observations carried out on shallow flows have revealed a particular dynamics: the vertical confinement can induce the formation of large horizontal vortices, which size greatly exceeds the depth. The aim of the thesis is to improve the knowledge of these physical processes in the case of a vortex dynamics generated by a turbulent impulsive jet. Two experimental campaign, one at small scale at the Master laboratory and the other one on the Coriolis turntable, have been performed to characterize the transition from a deep water layer to a shallow water layer. This transition is controlled by a dimensionless parameter we have called the confinement number C. When C is weak, the behaviour corresponds to three-dimensional turbulence, the water layer is deep. When C is great, the impulsive jet develops in a quasi-two-dimensional turbulence, the water layer is shallow. When the water layer is shallow, impulsive jets generate large horizontal vortices. A detailed study of these dipoles, laminar at small scale and turbulent at large scale, has shown the presence of a vertical circulation in the dipole front. The experimental results have been successfully compared with an original theoretical model
Chen, Qiang. "Modélisation numérique thermomécanique de fabrication additive par fusion sélective de lit de poudre par laser : Application aux matériaux céramiques". Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM004/document.
The application of SLM process is limited by the difficulty of process control. Its application to ceramics is especially challengeable due to their weak absorption to laser and weak resistance to thermal shock. The mastery of this process requires a full understanding of heat transfer, fluid dynamics in melt pool and solid mechanics. In this work, we propose a numerical model for the simulation of SLM process applied to ceramics. The model is developed at the track scale and with the assumption of continuous powder bed. It is based on level set method and multiphase homogenization, with which we are able to follow the evolution of gas/material interface and phase transformation. Simulations are performed to study the influence of material properties and process parameters on temperature, melt pool shape, fluid dynamics and solid mechanics. Apart from the laser power and scanning speed, material absorption is also found to be important to the thermal behavior and the melt pool shape. With the fluid dynamics, convex shape of track cross section is achieved under surface tension. Besides that, liquid droplets collapsing formed by the melting of powder create melt pool instability when falling, thus leading to track irregularity after solidification. The Marangoni effect, caused by surface tension gradient at gas/material interface, is investigated. Its influence on temperature distribution, melt pool shape and track regularity is recognized. One interesting finding is the smoothing effect of track surface with negative ∂γ/∂T. When combine surface tension with scanning speed, track surface becomes more irregular with the increase of scanning speed. The well-known balling effect is reproduced with high scanning speed. This can be helpful to find the regime for regular track shape with given laser power and scanning speed. Cracking defect is deleterious in additive manufacturing. The use of an auxiliary laser can help to avoid this defect by decreasing the maximum tensile stress. The process mode of this auxiliary laser remains an interesting subject to be studied and some guidelines have been given by the presented simulations. The model is validated by the comparison of melt pool shape with experiments under different process conditions. Simulations can also reveal the tendency of track surface variation for certain cases. By the application to multi-track deposition, the influence of hatch distance on layer surface, temperature and stress evolution is emphasized
Jenny, Mathieu. "Etude de la transition au chaos d'une sphère en ascension ou en chute libre dans un fluide newtonien". Université Louis Pasteur (Strasbourg) (1971-2008), 2003. http://www.theses.fr/2003STR13109.
Ferrato, Marc. "Extractions des auxiliaires organiques de mise en forme d'une poudre céramique à l'aide de fluides supercritiques". Limoges, 1995. http://www.theses.fr/1995LIMO0035.
Tanneur, Valérie. "Etude d’un contacteur à lit fluidisé en CO2 sous pression : Application à l'enrobage par le procédé RESS". Montpellier 2, 2006. http://www.theses.fr/2006MON20004.
Duloue, Muriel. "Analyse numérique des problèmes d'écoulement de fluides". Pau, 2000. http://www.theses.fr/2000PAUU3002.
Sriti, Mohammed. "Comportement statique et dynamique des joints labyrinthe". Lille 1, 1994. http://www.theses.fr/1994LIL10075.
Galliéro, Guillaume. "THERMODIFFUSION DANS LES FLUIDES DE LENNARD-JONES PAR DYNAMIQUE MOLECULAIRE". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2003. http://tel.archives-ouvertes.fr/tel-00325267.
Tangarife, Tomás. "Théorie cinétique et grandes déviations en dynamique des fluides géophysiques". Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL1037/document.
This thesis deals with the dynamics of geophysical turbulent flows at large scales, more particularly their organization into east-west parallel flows (zonal jets). These structures have the particularity to evolve much slower than the surrounding turbulence. Besides, over long time scales, abrupt transitions between different configurations of zonal jets are observed in some cases (multistability). Our approach consists in averaging the effect of fast turbulent degrees of freedom in order to obtain an effective description of the large scales of the flow, using stochastic averaging and the theory of large deviations. These tools provide theattractors, the typical fluctuations and the large fluctuations of jet dynamics. This allows to go beyond previous studies, which only describe the average jet dynamics. Our first result is an effective equation for the slow dynamics of jets, the validityof this equation is studied from a theoretical point of view, and the physical consequences are discussed. In order to describe the statistics of rare events such as abrupt transitions between different jet configurations, tools from large deviation theory are employed. Original methods are developped in order to implement this theory, those methods can be applied for instance in situations of multistability
Landeau, Maylis. "Deux aspects de la dynamique des fluides des noyaux planétaires". Paris, Institut de physique du globe, 2013. https://tel.archives-ouvertes.fr/tel-01472508.
Barthelet, Pierre. "Dynamique non linéaire des ondes interfaciales entre deux fluides cisaillés". Toulouse, INPT, 1995. http://www.theses.fr/1995INPT104H.
Galliéro, Guillaume. "Thermodiffusion dans les fluides de Lennard-Jones par dynamique moléculaire". Bordeaux 1, 2003. http://www.theses.fr/2003BOR12677.
This work is related to the study of thermal diffusion, or Soret effect, through numerical microscale simulations. This cross transport process couples mass flux and thermal gradient and is still largely misunderstood. For this study, we have applied a non equilibrium molecular dynamics algorithm on mixtures of Lennard-Jones spheres. At first we have tested the validity of our simulations. Then we have shown that the results allow us to estimate the thermal diffusion in these model fluids thanks to simple correlations on molecular parameters. This scheme has been successfully applied on ternary mixtures as well. Elsewhere, results in porous medium have shown that the influence of adsorption on thermal diffusion process is predominant compared to the one of the geometrical confinement, this influence being generally weak, except in the thinnest and in the most attractive slit pores
Kazerani, Dena. "Etudes mathématiques de fluides à frontières libres en dynamique incompressible". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066558/document.
This thesis is about theoretical study and numerical treatment of some problems raised in incompressible free-surface fluid dynamics. The first part concerns a model called the Green–Naghdi (GN) equations. Similarly to the non linear shallow water system (called also Saint-Venant system), the Green–Naghdi equations is a shallow water approximation of water waves problem. Indeed, GN equation is one order higher in approximation compared to Saint-Venant system. For this reason, it contains all the terms of Saint-Venant system in addition to some non linear third order dispersive terms. In other words, the GN equations is a dispersive perturbation of the Saint-Venant system. The latter system is hyperbolic and fits the general framework developed in the literature for hyperbolic systems. Particularly, it is entropic (in the sense of Lax) and symmertizable. Therefore, we can apply the well-posedness results known for symmetric hyperbolic system. During the first part of this work, we generalize the notion of symmetry to a more general type of equations including the GN system. This lets us to symmetrize the GN equation. Then, we use the suggested symmetric structure to obtain a global existence result for the system with a second order dissipative term by adapting the approach classically used for hyperbolic systems. The second part of this thesis concerns the numerical treatment of the free surface incompressible Navier–Stokes equation with surface tension. We use the level set formulation to represent the fluid free-surface. Thanks to this formulation, the kinematic boundary condition is treated by solving an advection equation satisfied by the level set function. This equation is solved on a computational domain containing the fluid domain over small time subintervals. Each iteration of the algorithm corresponds to the adevction of the fluid domain on a small time subinterval and to solve the time-discretized Navier–Stokes equations only on the fluid domain. The time discretization of the Navier–Stokes equation is done by the characteristic method. Then, the key tool which lets us solve this equation on the fluid domain is the anisotropic mesh adaptation. Indeed, at each iteration the mesh is adapted to the fluid domain such that we get convenient approximation and geometric errors in the vicinity of the fluid domain. This resolution is done using the Uzawa algorithm for a convenient finite element method. The slip boundary conditions are considered by adding a penalization term to the variational formulation associated to the problem
Montillet, Agnès. "Etude et modelisation de l'ecoulement a travers des milieux poreux reticules. Application a l'utilisation des mousses metalliques dans les reacteurs electrochimiques". Nantes, 1992. http://www.theses.fr/1992NANT2010.
Abaidi, Mohamed. "Instabilités morphologiques de micro-capsules en suspension libre dans un écoulement complexe". Amiens, 2013. http://www.theses.fr/2013AMIE0120.
Tamainot, Telto Zacharie. "Détendeurs thermostatiques de machines frigorifiques : Comportement dynamique et modélisation". Lyon, INSA, 1993. http://www.theses.fr/1993ISAL0100.
The development of a refrigerating machine operating with a variable-speed compressor requires the knowledge of the dynamic behaviour of every component, more particularly of the thermostatic expansion valve. The cooling capacity of the refrigerating system, with R-22 as refrigerant, is 6 kW. The behaviour of various thermostatic expansion valves (ballast charge, adsorbent charge and Moderated Operating Pressure or MOP charge) has been studied for compressor speed variations between 20% and 200%. This study bas shown the disadvantages of these expansion valves during dynamic operation. The decrease of the evaporating pressure, consecutive to a step or a ramp of the compressor speed, allows the suction of a two-phase fluid in the compressor. This phenomenon takes place particularly either for the low evaporating temperatures or for great variations of the compressor speed, more than 50%. To improve the operating conditions, many solutions have been considered as an electrical heating of the bulb. The best performances of the machine are obtained with the ballast charge expansion valve: cooling and heating outputs are respectively of 6 kW and 7,8 kW with a compressor power of 1,6 kW. The cooling capacity changes from 1 to 2,7 as the compressor speed is increased from 1000 to 3000 rpm. A steady-state mathematical model of a thermostatic expansion valve bas been developed. Simulation results are consistent with experimental data
Lornage, David. "Dynamique globale des lignes d'arbres de turbomachines couplées aux fluides environnants : application au cas des lames fluides". Lyon, INSA, 2001. http://theses.insa-lyon.fr/publication/2001ISAL0067/these.pdf.
High performances, reliability and security require predicting turbomachine behaviour with high accuracy. Concerning the dynamic behaviour of shaft lines, it is necessary to develop models including all possible couplings. In this context, the research presented in this thesis aims at developing a global model adapted to wheel/shaft assemblies rotating in a surrounding fluid. First, the use and advantages of Eulerian, Lagrangian and mixed formulations are recalled followed by a bibliographic review concerning classical techniques to solve structural problems are coupling techniques in rotating machinery. The coupling technique chosen is then described. It uses fluid and structural models developed and validated independently. The structural domain is discretised using the finite element method; the model is three dimensional. The fluid domain is discretised by using the finite difference method accounting for the thin fluid film hypotheses. A modal projection associated to a grip located at the interface of the fluid and structural domains allows efficient and adaptable coupling. The technique chosen is applied to three different test cases. The first two test cases are composed of a disc/shaft assembly coupled with, in the one hand, a fluid film between the disc and a casing and, on the other hand, a hydrodynamic bearing. These two applications are used to validate the method chosen. The third test case aims at studying a more realistic structure composed of a shaft and a wheel coupled with a fluid between the wheel and a casing. These three application make it possible to identify trends related to the effects of the fluid and the couplings between the flexible structural parts
Lornage, David Jacquet-Richardet Georges. "Dynamique globale des lignes d'arbres de turbomachines couplées aux fluides environnants application au cas des lames fluides /". [S.l.] : [s.n.], 2001. http://csidoc.insa-lyon.fr/these/2001/lornage/index.html.
Daniel, Eric. "Calcul de l'injection d'une phase dispersée dans un écoulement gazeux en tuyère". Aix-Marseille 1, 1992. http://www.theses.fr/1992AIX11035.
Léger, Bruno. "Etude dynamique et thermique d'un écoulement dans un canal symétrique semi-infini à parois ondulées ou corruguées". Pau, 1992. http://www.theses.fr/1992PAUU3014.
Dadi, Mohamed. "Etude de modèles de comportement de traceurs dans un écoulement et leur validation expérimentale par vélocimétrie holographique à expositions multiples". Lille 1, 1987. http://www.theses.fr/1987LIL10019.
Charki, Zakaria. "Analyse théorique du problème de la convection de Bénard profonde". Lille 1, 1994. http://www.theses.fr/1994LIL10009.
Boissière, Xavier. "Étude thermohydraulique d'un manchon thermique représentatif d'un bossage d'échangeur de chaleur". Nantes, 2003. http://www.theses.fr/2003NANT2010.