The current demands on Swedish steel industry to produce low quantity batches of specialized products requires research on steel casting processes. There are several physical processes that need be taken into account for this problem to be viewed in full light such as thermal-processes, solidification and fluid dynamics. This work focuses on the fluid-dynamics part; more specifically, the dependence of flow quality within the caster on nozzle and mould geometry. The simulations are carried out using a scale-resolving method, in specific LES (Large Eddy Simulation) which is coupled with a DPM (Discrete Phase Model) to model Argon behaviour. The results of these simulations are presented and validated against physical experiment and data from industrial trials. Conclusions are drawn regarding optimal nozzle types in respect to different mould geometries. The mould eigenfrequencies are shown to exhibit a connection with the casting velocity. This results in so called sweet spots in casting velocity where flow irregularities due to sloshing is minimal. It is shown that the mountain type nozzle is preferable for smaller geometries whilst comparatively larger geometries benefit from a cup type. / FLOWFLEX CC

Les non-linéarités des ondes de surface, qui se caractérisent par leur aspect dissymétrique, sont reconnues comme l'un des principaux moteurs du transport de sédiments en zone littorale. Cependant, l'estimation du transport reste imparfaite, en partie du fait d’une description inexacte des non-linéarités de la vitesse de l'écoulement orbital. Les ondes infra-gravitaires, qui coexistent avec les ondes courtes en zone littorale, sont des ondes de longue période (20-200 s) associés aux groupes d'ondes courtes. Les mécanismes de génération, propagation et dissipation de ces ondes sont maintenant relativement bien compris, mais leur effet sur le transport sédimentaire est encore mal connu. Afin (i) d’améliorer les paramétrisations existantes des non-linéarités de vitesse et (ii) d’étudier le rôle des ondes infra-gravitaires dans le transport sédimentaire, de nouvelles expériences ont été réalisées dans deux canaux à houle, l’un avec un fond fixe et l'autre avec un fond mobile constitué de sédiments de faible densité. Les données obtenues avec ces modèles physiques ont été utilisés conjointement à des données de terrain et des simulations numériques pour étudier les deux sujets.}TEXT{}{Les paramétrisations classiques pour les non-linéarités de vitesse prennent seulement en compte l'influence de paramètres locaux (la hauteur de vague, la longueur d'onde et la profondeur d’eau), ce qui entraîne des erreurs importantes dans les estimations, en particulier les valeurs maximales de non-linéarité. Ce travail montre que les non-linéarités de vitesse ont aussi une dépendance avec des paramètres qui ne sont pas locaux: (i) la cambrure de vague et (ii) la largeur de la bande spectrale au large, ainsi que (iii) la pente de la plage. Une nouvelle paramétrisation est proposée, qui réduit d’environ 50% l'erreur sur les résultats obtenus avec les paramétrisations existantes. Les résultats expérimentaux obtenus dans le canal à houle avec un fond mobile montrent que des conditions de vagues avec la même énergie d'ondes courtes, mais avec une modulation basse fréquence différente, modèlent des profils de plage différents. L'influence des ondes infra-gravitaires sur le transport sédimentaire est mis en évidence par deux mécanismes distincts: (i) l’advection par les ondes infra-gravitaires de sédiment mis en suspension par l'action des ondes courtes, qui dépend de la hauteur des ondes infra-gravitaires et de leur phase par rapport aux groupes d'ondes courtes et (ii) les ondes infra-gravitaires modifient les non-linéarités des ondes courtes, que ce soit directement ou indirectement, par modulation de la hauteur de la colonne d'eau. Les variations morphologiques du haut de plage induites par les ondes infra-gravitaires sont associées à des changements du profil de la plage dans les zones de déferlement et de levée, en mettant en évidence le lien entre les différentes régions du profil transversal de la plage. / Wave nonlinearities have long been recognised as being among the main drivers of sediment transport in the coastal zone. However, there are still significant errors in the prediction of this transport associated, partially due to inaccurate predictions of the velocity nonlinearities. The infragravity waves, which coexist with the short waves in the coastal zone, are long-period waves (with 20-200 s) associated to the short-wave groups. Their generation, propagation and dissipation mechanisms are already reasonably well understood, but their influence on sediment transport is still very poorly characterised. In order to (i) improve current predictions of velocity nonlinearities and (ii) investigate the role of infragravity waves in sediment transport, new experiments were carried out both in a fixed-bed wave flume and in a light-weight-sediment wave flume. The physical-modelling data set is used in combination with field data and numerical simulations for studying both subjects. Existing parameterizations of velocity nonlinearities account only for the influence of local wave parameters (e.g. wave height, wave length and water depth), which leads to considerable estimation errors, especially of the maximal values of nonlinearity. This work shows that the velocity nonlinearities depend also on non-local wave parameters: (i) offshore wave steepness, (ii) offshore spectral bandwidth and (iii) beach slope. A new parameterization is proposed, which reduces by about 50% the root-mean-square error relatively to former parameterizations. The experimental results in the light-weight-sediment wave flume demonstrate that wave conditions with the same short-wave energy, but different low-frequency modulation, shape different equilibrium beach profiles. The influence of the infragravity waves on the sediment transport is confirmed and depends on two different mechanisms: (i) advection of the short-wave suspended sediment by the infragravity-waves, which is dependent on the infragravity-wave height and phasing with the short-wave groups and (ii) modulation of short-wave nonlinearities by infragravity-wave motion, both directly and indirectly, through water-depth modulation. Changes in the beachface morphology induced by infragravity waves are connected to beach-profile changes in the surf and inner-shoaling zones, highlighting the existent link between the different zones of the cross-shore beach profile.

Tsunami are a fascinating but potentially devastating natural phenomena that have occurred regularly throughout history along New Zealand's shorelines, and around the world. With increasing population and the construction of infrastructure in coastal zones, the effect of these large waves has become a major concern. Many natural phenomena are capable of creating tsunami. Of particular concern is the underwater landslide-induced tsunami, due to the potentially short warning before waves reach the shore. The aims of this research are to generate a quality benchmark dataset suitable for comprehensive comparisons with numerical model results and to increase our understanding of the physical processes involved in tsunami generation. The two-dimensional experimental configuration is based on a benchmark configuration described in the scientific literature, consisting of a semi-elliptical prism sliding down a submerged 15° slope. A unique feature of these experiments is the method developed to measure water surface variation continuously in both space and time. Water levels are obtained using an optical technique based on laser induced fluorescence, which is shown to be comparable in accuracy and resolution to traditional electrical point wave gauges. In the experiments, the landslide density and initial submergence are varied and detailed measurements of wave heights, lengths, propagation speeds, and shore run-up are made. Particle tracking velocimetry is used to record the landslide kinematics and sub-surface water velocities. Particular attention is paid to maintaining a high level of test repeatability throughout the experimental process. The experimental results show that a region of high pressure ahead of the landslide forces up the water over the front half of the landslide to form the leading wave crest, which propagates ahead of the landslide. The accelerating fluid above, and the turbulent wake behind, the moving landslide create a region of low pressure, which draws down the water surface above the rear half of the landslide to form the leading trough. Differences in the phase and group velocities of the components in the wave packet cause waves to be continually generated on the trailing end of the wave train. The downstream position that these waves form continually moves downstream with time and the wave packet is found to be highly dispersive. The interaction of the landslide pressure field with the free surface wave pressure field is important, as the location of the low pressure around the landslide relative to the wave field acts to reinforce or suppress the waves above. This has a substantial effect on the increase or decrease in wave potential energy. When the low pressure acts to draw down a wave trough, the wave potential energy increases. When the low pressure is below a wave crest, it acts to suppress the crest amplitude, leading to an overall decrease in wave potential energy. Measurements of the efficiency of energy transfer from the landslide to the wave field show that the ratio of maximum wave potential energy to maximum landslide kinetic energy is between 0.028 and 0.138, and tends to increase for shallower initial landslide submergences and heavier specific gravities. The ratio of maximum wave potential energy to maximum landslide potential energy ranges between 0.011 and 0.059 and tends to be greater for shallower initial submergences. For two experimental configurations the ratio of maximum wave potential energy to maximum fluid kinetic energy is estimated to be 0.435 and 0.588. The wave trough initially generated above the rear end of the landslide propagates in both onshore and offshore directions. The onshore-propagating trough causes a large initial draw-down at the shore. The magnitude of the maximum draw-down is related to the maximum amplitude of the offshore-propagating first wave trough. A wave crest generated by the landslide as it decelerates at the bottom of the slope causes the maximum wave run-up observed at the shore. A semi-analytical model, based on inviscid and irrotational theory, is used to investigate the wave generation process of a moving submerged object in a constant depth channel. The simplified geometry allows a variety of phenomena, observed during the experimental tests, to be investigated further in a more controlled setting. The variations in the growth, magnitude, and decay of energy as a function of time is due the interaction of the pressure distribution surrounding the moving slider with the wave field, in particular, the leading crest and trough. The largest energy transfer between slider kinetic energy and wave potential energy occurs when there is prolonged interaction between the slider's low pressure region and the leading wave trough. The generation of onshore propagating waves by a decelerating landslide is confirmed, and the magnitude of the maximum wave run-up is found to be dependent on the magnitude of the slider deceleration. The model also shows that slides with Froude number close to unity convert substantial amounts of energy into offshore propagating waves. The onshore propagating wave potential energy is not as sensitive to Froude number. A further result from the model simulations is that the specific shape of the slider has only a minor influence on the wave response, provided the slider's length and area are known. A boundary element model, based on inviscid and irrotational theory, is used to simulate the laboratory experiments. Model predictions of the wave field are generally accurate, particularly the magnitude and range of wave amplitudes within the wave packet, the arrival time of the wave group, the amplitude of the run-up and run-down at the shore, the time the maximum run-down occurs, and the form and magnitude of the wave potential energy time history. The ratios of maximum wave potential energy to maximum slider kinetic energy are predicted to within ± 29%. The model predictions of the crest arrival times are within 3.6% of the measured times. The inability of the inviscid and irrotational model to simulate the flow separation and wake motions lead to a 45% under prediction of the maximum fluid kinetic energy. Both the semi-analytical and BEM models highlight the need for the correct specification of initial slider accelerations in numerical simulations in order to accurately predict the wave energy.

Model based techniques for automated condition monitoring of HVAC systems have been under development for some years. Results from the application of these methods to systems installed in real buildings have highlighted robustness and sensitivity issues. The generation of false alarms has been identified as a principal factor affecting the potential usefulness of condition monitoring in HVAC applications. The robustness issue is a direct result of the uncertain measurements and the lack of experimental control that axe characteristic of HVAC systems. This thesis investigates the uncertainties associated with implementing a condition monitoring scheme based on simple first principles models in HVAC subsystems installed in real buildings. The uncertainties present in typical HVAC control system measurements are evaluated. A sensor validation methodology is developed and applied to a cooling coil subsystem installed in a real building. The uncertainty in steady-state analysis based on transient data is investigated. The uncertainties in the simplifications and assumptions associated with the derivation of simple first principles based models of heat-exchangers are established. A subsystem model is developed and calibrated to the test system. The relationship between the uncertainties in the calibration data and the parameter estimates are investigated. The uncertainties from all sources are evaluated and used to generate a robust indication of the subsystem condition. The sensitivity and robustness of the scheme is analysed based on faults implemented in the test system during summer, winter and spring conditions.

Investigations into the turbulent flows in uniform and nonuniform open channels by previous researchers have demonstrated the requirement and importance of understanding the turbulence structures and energy losses due to irregularity in non- uniform open channels. Responding to this requirement, the turbulent flow in one special non-uniform open channel has been studied both experimentally and numerically. This non-uniform open channel was designed so that its width and bed level vary while its cross-sectional area below the water surface keeps constant. An upstream uniforzn open channel is attached to the non-uniform open channel to establish fully developed turbulent flow conditions. A downstream uniform channel is also attached for control of water depth and downstream flow condition. The experimental study consisted of measurements of turbulent velocity field with a LDV (Laser Doppler Velocimetry) and measurements of boundary shear stress (BSS) with Roving Preston tubes in the experimental channel. Turbulent velocity components in the longitudinal and vertical directions were measured with the LDV in forward scattering mode and the laser beams were focused from the channel side wall into the water. Turbulent velocity components in the longitudinal and transverse directions were measured with the LDV in back scattering mode and the laser beams are focused from above the water surface into the water. Both the forward scattering mode measurements and the back scattering mode measurements were taken at two cross sections in the upstream uniform open-channel and at twelve cross sections in the nonuniform open channel. Obtained data include mean longitudinal velocity U, transverse velocity V, vertical velocity W, turbulence intensities u^2, v^2, w^2, and Reynolds shear stresses -uv and -uw. The chief results of these measurements are: 1) There is no separation of flow in the nonuniform open channel. 2) As flow passes from wider and shallower section to narrower and deeper section, it responds as though it experiences contraction in horizontal planes and expansion in vertical planes. The reverse occurs as flow passes from narrower and deeper section to wider and shallower section; 3) The secondary currents in the nonuniform open channel are combinations of the effects of pure contraction and expansion of channel boundaries and the effects of the vortex kind secondary currents; 4) Turbulence intensities in the non-uniform open channel show similar distribution patterns to that in the uniform open-channel but their magnitudes change due to the change of channel shape; 5) Negative values of the Reynolds shear stresses, -uw, appear at the free surface and may extend to a large depth below the free surface in the nonuniform open channel. Boundary shear stresses in the experimental channel were measured with Roving Preston tubes. The use of the Roving Preston tubes was preceded with calibrations of themselves in air pipe flow and calibrations of a special pressure transducer in air and in water. Delicate measurement procedures were designed for measurements of BSS in the nonuniform open channel. The BSS were measured at one cross section in the uniform open-channel and at twelve cross sections in the nonuniform open channel. The chief results of these measurements are: 1) The irregularity of the nonuniform open channel significantly affects the distribution of the BSS but the total shear force has little change; 2) The effect of the secondary currents on the BSS is very similar to the effect of secondary currents on the ESS in uniform open channel; 3) The irregularity in the non-uniform open channel does not cause extra energy loss since there is no flow separation. The numerical study made use of a FEM (finite element method) commercial package FIDAP to simulate the turbulent flows in the experimental channel. These simulations are carried out with Speziale's eddy-viscosity anisotropic k-E model, the standard k-E model, and the RNG model. With each model, simulations were undertaken for four consecutive uniform channels of 5 m length so that fully developed turbulent flow conditions were established before entering into the simulation of flow in the non- uniform channel. In all simulations the free surfaces were fixed. Simulation results include U, V, W, k, and E. For turbulent flow in the uniform channel, only Speziale's model is capable of predicting qualitatively correct secondary currents. For turbulent flow in the non-uniform open channel, all three models gave similar simulation results. The calculated distribution patterns of U and W are in agreement with measurements except near the free surface but differences exist in magnitude. None of the three models was capable of modelling the transverse velocity V in the nonuniform open channel correctly. Further simulations are necessary with movable free surface and better boundary condition for the energy dissipation rate s in order to achieve better agreement with the experimental values, especially near the free surface.

Mobile offshore jack-up drilling rigs are not custom-designed for a particular location but rated for typical operating characteristics, like water depths. They may be deployed at a number of different sites during their design life. Under the current guidelines, the jack-up is required to be assessed for its suitability for each new proposed location, assuming environmental loading conditions due to wind, waves and current corresponding to a 50-year return period storm applicable to the site. Traditionally, these assessments have been performed in two dimensions, simplifying the jack-up to a plane frame and the loading conditions to be in-plane with the rig's 'axis of symmetry'. This thesis introduces a computer program, named SOS_3D, for the fluid-structure-soil interaction analysis of jack-up response in three dimensions. Extensive experimental series have been performed to provide evidence for the generalisation of the foundationsoil interaction model to general six degree-of-freedom loading conditions and its applicability to load paths and stress levels relevant to jack-up spudcans. These experiments included (1) 1g single footing tests, (2) centrifuge single footing tests and (3) centrifuge model jack-up tests. The latter tests highlighted differences in response and mode of failure depending on the loading direction of the jack-up and re-iterated the importance of three-dimensional modelling. The numerical program SOS_3D introduced early in this thesis was shown to represent a useful tool for the prediction of jack-up behaviour under general combined loading in three dimensions. It provided reasonably good, conservative predictions of the experimentally measured jack-up behaviour.

Une des méthodes les plus populaires et largement utilisée pour l’amélioration des sols compressibles est la technique d'inclusions rigides verticales qui constitue une alternative intéressante aux techniques plus traditionnelles telles que le pré-chargement, la mise en place de drains verticaux, le remplacement du sol en place, etc.Le Projet National ASIRI (Amélioration du Sol par Inclusions Rigides) a permis d’apporter des réponses sur le comportement de cette technique de renforcement et d’établir des recommandations de dimensionnement et de réalisation. Celui-ci comprend un volet expérimental (expérimentations en vraie grandeur, modèles physiques réduits à 1g, études en chambre d’étalonnage) et un volet numérique. Cependant, les recommandations publiées par ASIRI sont limitées aux cas de chargement monotone. Pourtant, différents cas de structures sous chargement cyclique sont couramment rencontrés dans la pratique: chargement des vagues sur les structures offshore, force du vent, charge sismique, la charge de trafic, remplissage et vidange de réservoirs, chargement et déchargement des zones de stockage… Cela nécessite alors de comprendre le comportement sous chargement cyclique et/ou dynamique de ces ouvrages.Ce travail de thèse constitue une contribution à la compréhension du comportement de ce type d’ouvrage, et s’intéresse plus particulièrement à la modélisation des mécanismes qui se développent dans le matelas de transfert de charge lors d’un chargement cyclique vertical quasi-statique. Il se fait suivant deux approches complémentaires : Expérimentale : par des essais sur un nouveau modèle physique réduit tridimensionnel à 1g et à l’échelle 1/10ème, Numérique : par la modélisation numérique tridimensionnelle en milieu continu utilisant le logiciel FLAC3D.Dans un premier temps, le travail expérimental réalisé nous a permis d’étudier le comportement de cette technique de renforcement sous chargement monotone et cyclique mettant en œuvre la méthode de corrélations d’images. La modélisation physique réalisée nous a permis d’étudier l’influence de l’épaisseur de la plateforme de transfert de charge granulaire et des conditions aux limites (cas remblai/cas dallage).Dans un deuxième temps, les résultats expérimentaux nous ont servi comme une base de données pour la validation d’un modèle numérique en milieu continu. La première étape de la modélisation numérique consiste à valider un modèle numérique à la même échelle réduite du modèle physique. La validation de l’approche de modélisation numérique à échelle réduite nous a permis, dans une deuxième étape, de réaliser une étude paramétrique afin de déterminer l’influence des différents paramètres sur le comportement du système. / One of the most popular and widely used methods for soft soil improvement is the reinforcement using vertical rigid inclusions. It constitutes an interesting alternative to the other traditional techniques such as preloading, vertical drains, replacing soil etc...The national French project ASIRI (Amélioration du Sol par Inclusions Rigides) allowed to provide answers about the behavior of this technique and to establish recommendations for design and construction. It included an experimental part (full-scale, 1g physical model experiments and calibration chamber studies) and a numerical part. However, the recommendations established by ASIRI are limited to the case of monotonic loading. Yet, various cases of structures under cyclic loading are commonly encountered in practice: waves loading on offshore structures, wind strength, seismic load, traffic load, filling and emptying of tanks, loading and unloading of storage areas... This then requires the understanding of the behavior of this technique under cyclic and/or dynamic loading.The work done in this thesis constitutes a contribution to understanding the behavior of this type of structures, and is particularly interested in modeling the mechanisms that develop in the load transfer mattress under a quasi-static vertical cyclic loading . Two complementary approaches have been followed: Experimental: by performing experimental tests using a new 1g tridimensional physical model with a scale factor of 1/10, Numerical: by performing numerical tridimensional simulations in a continuous media using the software FLAC3D.At first, the experimental work has allowed us to study the behavior of this reinforcement technique under monotonic and cyclic loading implementing the digital image correlation method. A parametric study performed with the physical modeling allowed us to study the influence of the granular load transfer platform (LTP) and the boundary conditions (presence of a rigid slab at the surface of the LTP).Secondly, the experimental results have served as a database for the validation of a numerical model in continuous medium. The first step of the numerical modeling is to validate a numerical model at the same reduced scale of the physical model. The validation of the numerical modeling approach at the reduced scale allowed us in a second step to perform a parametric study in order to determine the influence of different parameters on the behavior of the system.

Cette thèse présente une étude expérimentale des mécanismes contrôlant la réponse macroscopique d’une interface sable-pieu sous sollicitations axiales monotones et cycliques. Une approche innovante associant la tomographie rayons X à des outils avancés d’analyses d’images en trois dimensions (3D) est utilisée dans le but d’extraire des informations à différentes échelles, notamment à l’échelle micro. L’analyse quantitative du comportement individuel des grains situés au voisinage du pieu fournit une collection de données 3D qui pourraient être utilisées pour la validation de modèles numériques ou théoriques.Une série de tests est réalisée sur un pieu instrumenté à pointe conique installé par vérinage monotone dans un échantillon dense de sable calcaire. Après l’installation, le pieu est soumis à un grand nombre de cycles axiaux contrôlés en déplacements (jusqu’à 2000 cycles), à contraintes constantes. Ces essais ont été conduits dans une mini chambre de calibration qui permet d’acquérir des tomographies rayons X à haute résolution après différentes étapes de chargement. Il est admis que le dispositif expérimental n’est pas représentatif des conditions d’essais sur pieux in-situ pour les raisons principales suivantes : le ratio entre le diamètre de la chambre le diamètre du pieu et le ratio entre le diamètre du pieu et la taille moyenne des grains sont bien inférieurs aux ratios recommandés dans la littérature afin de limiter les effets d’échelle. Par conséquent, les résultats obtenus dans ce travail ne peuvent et ne doivent pas être directement extrapolés pour le design de pieux réels. Cependant, un tel dispositif permet de reproduire qualitativement des tendances similaires à celles observées à l’échelle macro sur des essais à grande échelle et d’observer des mécanismes se déroulant à l’échelle micro.Les images 3D obtenues par reconstruction des tomographies rayons X sont utilisées afin d’identifier et de suivre l’évolution des grains individuels. Le champ cinématique complet en 3D est mesuré grâce à un code de corrélation d’images numériques 3D (DIC), « TomoWarp2 ». Des outils de traitement d’image sont également employés pour suivre les changements de porosité et la production de fines par broyage des grains à l’interface.Pendant la mise en place du pieu, plusieurs zones où les déplacements se concentrent sont identifiées. Une recirculation des grains le long du fût du pieu est mise en évidence. Globalement, le sable a un comportement dilatant à l’exception d’une fine couche (épaisseur d’environ 3 à 4·D50) autour du pieu où les fines sont produites. Pendant les cycles, la réponse macroscopique de l’interface montre une évolution en deux phases, avec une augmentation non négligeable de la résistance du fût dans la seconde phase. Pour ces deux phases, la mesure de la cinématique granulaire révèle un comportement du sol différent associé à une densification importante à l’interface. Dans la première phase, le sol se contracte radialement dans une zone de 4·D50 d’épaisseur. Ce phénomène est certainement dû au réarrangement granulaire mesuré par DIC. Dans la seconde phase, les grains de sables se déplacent difficilement et la densité à l’interface atteint un seuil pour lequel le frottement sur le pieu augmente de manière significative. / This doctoral work presents an experimental investigation into the mechanisms governing the macroscopic response of sand-pile interface during monotonic installation and subsequent axial cyclic loading. An innovative approach combining x-ray tomography and advanced image analysis tools is employed to extract information at different scales, including the micro-scale. A quantitative analysis of the behavior of individual sand grains in the vicinity of the pile offers valuable three-dimensional (3D) data set against which theoretical or numerical approaches could be tested.A series of tests is run on an instrumented close-ended conical model pile installed by monotonic jacking in a dense calcareous sand sample. Following the installation, the model pile is submitted to a large number of axial displacement-controlled loading cycles (a few thousands cycles) under constant normal stress. The tests are performed in a mini-calibration chamber that allows the acquisition of high resolution x-ray images at different stages of the loading. The chamber is admittedly not representative of field pile testing conditions for the main following reasons: the calibration chamber-to-pile diameter ratio and the sand particle-to-pile diameter ratio are far below the ratios recommended in the literature to limit scale effects on the interface response. Consequently, the results presented in this work can not, and should not, be directly extrapolated to field pile design. Yet, such a setup is able to reproduce qualitatively trends that are similar to those obtained at the macro-scale on large-scale experiments and allows the observation of full-field mechanisms taking place at the micro-scale.3D images resulting from the reconstruction of the x-ray scans are used to identify and follow the evolution of individual sand grains. Full-kinematics are measured thanks to a 3D Digital image Correlation (DIC) code, “TomoWarp2”. Image processing tools are also employed to measure local porosity changes and the production of fines by grain crushing at the interface.During pile installation, different zones where grains displacements concentrate are identified. A recirculation of the grains alongside the pile is also observed. Globally, the sand mass exhibits a dilative behavior except within a relatively thin layer (about 3 to 4·D50 thickness) around the model pile where grain crushing occurs. During subsequent loading cycles, the macroscopic response of sand-pile interface shows a two-phases evolution, with a non negligible increase of shaft resistance in the latter phase. For these two phases, the measurement of grain kinematics reveals a different behavior of the sand mass associated with a significant densification at the interface. In the first phase, the sand mass contracts radially within a region of thickness 4·D50. This mechanism is likely due to inter-granular rearrangement as measure by DIC. In the second phase, sand grains hardly move and the sand mass reaches a threshold density for which the friction on the shaft starts to increase substantially.

Dans cette recherche, nous étudions les problèmes de modélisation de discontinuités topologiques d'objets physiques déformables. Parmi toutes les discontinuités topologiques possibles, nous nous intéressons à celles que nous avons qualifiées de « discontinuités de 1 vers N » dans le contexte de la modélisation physique. Entrent dans cette catégorie les phénomènes de fractures, de cassures, de déchirures et de fissures. De nombreux travaux se sont intéressés à la modélisation et la simulation de ce type de phénomènes. Plusieurs méthodes ont été proposées, à partir de systèmes de modélisation différents parmi lesquels les plus courants sont : modélisation masses – ressorts sur maillages, méthodes d'éléments finis avec et sans maillage. Une question commune qui se pose dans toutes les méthodes discutées dans cette thèse est la question des endroits fonctionnels où apparaissent et se propagent les discontinuités topologiques. Nous étudions ce problème à travers plusieurs approches sur la modélisation physique de discontinuités topologiques. Nous proposons ensuite notre approche, qui se fonde sur le formalisme masses – interactions. Nous montrons en quoi ce type de modélisation offre certaines propriétés natives pour traiter cette question. En particulier, le fait qu'elles soient par principe affranchies de toute notion de contigüité spatiale et de continuité matérielle leur permet de poser de manière très générale la question des changements d'état physique à l'origine des discontinuités topologiques observées. Nous montrons qu'une très grande majorité de changements d'états physiques peuvent se modéliser par des variations des paramètres physiques d'interactions physiques non linéaires en lieu et place de changements structurels adoptés dans majorité des travaux menés par des méthodes courante et qui conduisent à des modifications très importantes et complexes du modèle physique. Néanmoins, cela induit, des effets d'enlèvements de matière aux endroits du changement d'état puisque celui –ci est porté par l'interaction, c'est à dire une contrainte physique qui est placée entre les points matériels. Pour s'affranchir de ces effets, nous proposons alors une nouvelle méthode, qui consiste à modéliser les discontinuités topologiques sur un élément de masse physique et non pas sur un élément de contrainte physique. Nous appelons ce dispositif « MAT éclatable ». Le processus de modélisation avec les MAT éclatables s'inscrit dans le processus de modélisation masses-interactions tel que défini dans le formalisme de modélisation et de simulation de CORDIS – ANIMA. La méthode proposée permet d'effectuer des changements topologiques par modèle physique par changements structurels, mais différemment de ceux plus couramment effectuées dans les méthodes usuelles (tels que par exemple, ajout ou suppression de ressorts ou de masses), la méthode des MAT éclatables permet de maîtriser le fonctionnement du modèle physique en termes d'optimalité des transformations, de stabilité du temps de calcul et de stabilité numérique. La méthode des MAT éclatables a été développée sous forme d'un dispositif de modélisation, destiné aux utilisateurs de notre outil de modélisation CORDIS-ANIMA. Pour illustrer et valider la méthode, nous proposons un ensemble de modèles physiques modélisation des fractures et déchirures multiples apparaissant et se propageant dans des objets très déformables, des effilochures, ou des fragmentations. / L'auteur n'a pas fourni de résumé en anglais

Made available in DSpace on 2015-03-13T17:08:13Z (GMT). No. of bitstreams: 1 RafaelaAP.pdf: 4484951 bytes, checksum: 404fda9fc50481c6bc56cdc75726d9f8 (MD5) Previous issue date: 2008-03-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / As bacias do tipo rifte se tornaram o foco de muitas pesquisas, intensificadas nas ?ltimas d?cadas, n?o apenas por sua ampla distribui??o global e grande versatilidade em termos de ambi?ncia geotect?nica, mas tamb?m por sua import?ncia econ?mica na ind?stria de explora??o de hidrocarbonetos. Neste contexto, a utiliza??o do aparato tipo caixa-de-areia se tornou uma ferramenta potencial para simular a deforma??o distensional em bacias sedimentares e vem agregando conhecimento e informa??o acerca das caracter?sticas das estruturas desenvolvidas nestes ambientes. No presente trabalho, a t?cnica da modelagem f?sica, realizada em caixa-de-areia , foi utilizada para estudar a nuclea??o e desenvolvimento das falhas durante a simula??o de rifteamentos obl?quos e ortogonais. Os experimentos distensionais foram constru?dos de modo a induzir a deforma??o homog?nea, localizada (S?ries I e II) e distribu?da (S?rie III), em um pacote rochoso simulado, principalmente, por camadas de areia. As estruturas presentes nos modelos estudados s?o influenciadas por tr?s vari?veis principais: a obliq?idade de distens?o (?ngulo agudo entre a dire??o de distens?o e o eixo do rifte), o mergulho da descontinuidade pr?via (aqui denominada falha-mestra = FM) e a mudan?a na geometria do substrato. Os modelos foram agrupados em tr?s s?ries experimentais caracterizadas por: (1) S?rie I: experimentos de rifteamento ortogonal e obl?quo que testam a influ?ncia de uma trama pret?rita (FM) no desenvolvimento do rifte; (2) S?rie II: experimentos de rifteamento ortogonal e obl?quo sem a influ?ncia de tramas pret?ritas e (3) S?rie III: experimentos de rifteamento obl?quo focando a deforma??o distribu?da em seq??ncias homog?neas (somente areia) e heterog?neas (areia + microesferas de vidro). Uma observa??o geral e comum a todos os modelos ? que as falhas nucleadas s?o inicialmente segmentadas, desenvolvendo tra?os alongados decorrentes da propaga??o e intera??o dos segmentos. As falhas observadas t?m car?ter redominantemente normal, mas a contribui??o de um componente direcional ? mapeada nos modelos obl?quos. Os modelos da S?rie III apresentaram um n?mero muito maior de falhas desenvolvidas como fruto da deforma??o distribu?da, al?m de apresentarem geometria escalonada mais freq?ente. De forma geral, grande parte dos segmentos de falhas se desenvolve paralelamente ? dire??o da descontinuidade induzida que condiciona a dire??o do eixo do rifte nos modelos das tr?s s?ries estudadas, embora segmentos obl?quos (variando ?20?) tamb?m ocorram. As falhas normais s?o nucleadas com ?ngulos de mergulho moderado a alto e freq?entemente s?o rotacionadas ao longo da deforma??o. O desenvolvimento de falhas mais tardias, que ocorre preferencialmente na por??o intra-rifte, concentra e acomoda a deforma??o, e al?m de apresentarem ?ngulo de mergulho maior que as anteriores, tamb?m tendem a rotacion?-las. As falhas de borda dos riftes apresentam comportamentos distintos, com as falhas da borda leste mantendo-se ativas e exibindo maior rota??o, enquanto que as falhas da borda oeste apresentam pouco aumento do rejeito e tendem ? estabilidade durante a progress?o da deforma??o. A largura da zona de rifteamento (w) apresenta uma rela??o de depend?ncia com as vari?veis condicionantes dos modelos: quanto maior o mergulho de FM menor ser? o valor de w, quanto mais obl?qua a distens?o menor ser? o w, e finalmente, w ? muito menor nos experimentos cuja deforma??o ? localizada (S?ries I e II) quando comparado ?queles cuja deforma??o ? distribu?da (S?rie III). Estruturas mais discretas, tipo zonas de transfer?ncia (conjugadas e divergentes), s?o observadas nos modelos obl?quos das S?ries II e III, interpretadas como o produto da intera??o entre as extremidades de falhas de mergulho opostos. O desenvolvimento, geometria e cinem?tica das falhas distensionais, e seus par?metros intr?nsecos discutidos ao longo deste trabalho, influenciam direta ou indiretamente no desenvolvimento de condutos, barreiras e armadilhas ao fluxo de fluidos, e podem ter impacto consider?vel na explora??o econ?mica de bacias sedimentares. Sendo assim, a modelagem f?sica de an?logos, abordando os aspectos pertinentes que influenciam no arcabou?o estrutural de bacias com potencial econ?mico, ? uma ferramenta que pode ser amplamente empregada no aux?lio ao entendimento da distribui??o espa?o-temporal de falhamentos e impactar diretamente na explora??o/explota??o de hidrocarbonetos, por exemplo.