Dissertations / Theses on the topic 'Modélisation numérique discrète (DEM)'
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Nguyen, Minh-Duc. "Modélisation numérique discrète des matériaux bitumeux." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSET003/document.
Bituminous mixtures have traditionally been used in road constructions and recently under railway ballast. Its high rigidity at relatively low ambient temperatures and high frequency explains its widespread application in northern Europe. This material has been studied at the global level by both empirical, experimental and analytical approaches. However, the asphalt has a heterogeneous internal structure and complex which may cause complex behavior. The analysis at the local level then make it possible to supplement the knowledge of its behaviors.Nowadays, the method of discrete elements is known as a numerical tool spread in the granular field. It can model its behavior through local models and provide information about its internal structure. On the one hand, this method considers that the particles are quasi-solid. Its displacement is governed by the laws of motion. On the other hand, the overlap at the particle contact level is allowed. The interpenetration of the particles is calculated by the associated local contact laws. This thesis constitutes a numerical model of bituminous mixes whose isolated particles interact through laws of interaction at a distance. This model takes into account the granulometry of the aggregates (> 1 mm) and its volume ratio with respect to the mastic constituted by grains (<1 mm), the binder and voids. The aggregates (> 1 mm) alone are modeled by numerical particles, while mastic is taken into account by laws of interaction.First, an elastic simulation is performed in order to reproduce the elastic asymptotic behaviors of a reference bituminous mix of GB3 type that appear during extreme conditions (frequency or temperature). Elastic interaction laws have applied to the created numerical model. In both normal and tangential directions, the stiffness of the spring and its ratio are constant.Then, the viscoelastic simulations are performed to reproduce the viscoelastic behavior of the same reference material. At first, a Kelvin-Voigt interaction law is used to qualitatively highlight the application of a viscoelastic law. Then, the global viscoelastic behavior is modeled at the level of the particles by some laws of interaction of type 1KV1R (a Kelvin-Voigt and a spring in series) leaving again to the network of interaction of the numerical model. The stiffness of the springs taking into account the geometry of the particle interface is constant for all models of 1KV1R. However, the viscosities of the dashpots are different. Some hypotheses are examined to distribute its viscosities in the interaction network. At the end of the studies, the analysis of the internal efforts are carried out
Fakih, Mahmoud. "Modélisation numérique discrète de la croissance racinaire dans un sol : relation force-forme." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT323/document.
Plant roots play an important role in the growth and development of plants, and it is well known that the mechanical interactions between a growing root and the surrounding soil can have a major impact on root growth and consequently on plant biomass production. These mechanical interactions are one of numerous factors that explain the variability of root architecture, including genetics, environment and developmental instability. But this factor has often been under-estimated. I hypothesize that the heterogeneous structure of soil at the particle scale, demonstrated by the broad distribution of forces, can significantly influence root growth trajectories. This thesis aims at determining how grains in granular soils are reorganized under the action of growing roots, and in return how the resulting forces acting on root tips modify their development, including the kinematics of their trajectories, in order to develop a general biophysical law of root-soil mechanical interactions. I developed a 2D numerical model of root growth in a granular medium using a Discrete Element Model (DEM). The model is able to compute grain-grain and root-grain contact forces within a granular medium. The root system is modelled using chains of connected spheroline elements. The orientation of root growth at every growth step is determined by the dynamics of the whole root under the action of its internal elastic forces and reaction forces exerted by the grains, which are the mechanical interactions that control numerical growth in the model.Parametric studies were carried out in order to (i) estimate the influence of granular structure (grain diameter distribution, cohesion, volume fraction) and root mechanical properties (root bending stiffness) on the axial force signal acting on the root tip, and on the root trajectories and (ii) define general physical laws that can be used further to analyze experimental data. The distribution curves of computed root tip-grain forces normalized by the mean force during a given period of growth were characterized by a decreasing power law for forces below the mean force, and an exponential fall-off for forces above the mean force, thus reflecting the broad distribution of forces inside the granular material. An analysis of the standard deviation of the local deformations of root trajectories resulted in two different regimes with regard root stiffness. In the first regime, soil controlled the root deformation and in the second, the root trajectory was straighter and displaced more significantly the surrounding grains during growth
Al, Tfaily Bilal. "Capacité prévisionnelle de la modélisation discrète pour application aux ouvrages géotechniques complexes." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALI077.
Geotechnical engineering is a crucial field in the design and construction of foundations, embankments, tunnels, and other structures interacting with soil and rock. However, the description of the elastoplastic response of soil, with preponderant non-linear and non-reversible deformations together with a non-associative flow rule, is complex. The difficulty is even higher in the case of non-monotonous loading paths where phenomenological constitutive relations require ad-hoc history parameters and advanced experimental tests for their calibration.Discrete element method has been proved to be an effective method in predicting quantitatively the constitutive response of soils, even in the case of complex loadings (with rotation of principal stress directions, or loading/unloading cycles) where conventional elastoplastic constitutive relations may fail to simulate realistic responses. For granular soils with a narrow grading, a direct representation of soil grains by polyhedral particles or with the level set method is possible, whereas for finer soils, or soils with a wider grading, alternative solutions should be considered. Spherical particles with enriched contact laws (e.g. by introducing rolling resistance at the contact) or rather simplified clumps of spheres can be used to keep the model relatively light to tackle further boundary value problems with limited computational cost. However, even if the models provide satisfying results for direct shear tests or drained triaxial compression loading paths compared to experimental measurements, their validation with respect to more complex loading paths as the isochoric compression or the path at constant stress deviator still present difficulties, in particular for initially loose granular assemblies.First, this study aims to compare such different approaches in terms of the prediction abilities at the macroscopic scale of the constitutive responses of soils, particularly for complex loading paths. Two kinds of discrete models are considered: (i) spherical particles with rolling resistance, (ii) simple clumps made of 2 to 6 spheres. The models are calibrated from two drained triaxial compressions on dense and loose Hostun sand. They are then assessed, according to the macroscopic response, on loading paths significantly different from the calibration loading paths (isochoric compressions, circular stress paths in the deviatoric plane, constant deviatoric stress path, etc.).Then, we investigate the importance of the description of the anisotropy of the initial fabric and of the inter-particle friction law in the simulated responses of loose granular assembly to different kinds of loading paths. It shows how the combination of both can modify importantly the simulated responses to some kinds of loading paths. This investigation is carried out for a numerical discrete model made of spheres by comparison with experimental results on sand.Finally, the model is used to simulate the nonlinear interaction between a shallow foundation of building structure and the supporting soil during strong seismic loadings, as tested experimentally for the TRISEE project with a full scale physical model. An adaptative discretization technique is implemented to limit the number of particles in such a boundary value problem and make the computation possible with a conventional desktop computer. Numerical results are benchmarked against experimental measurements from the TRISEE project, and FEM numerical simulations or macro-element models
Tran, Duc Kien. "Modélisation numérique discrète de l'érosion interne par renard hydraulique dans les barrages ou digues en terre." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC055/document.
The work reported in this thesis consists in a discrete modelling of the backward front propagation of an erosion pipe, as can take place in embankment dams or dikes. Some numerical tools have been developed to this end, based on the coupling between the Discrete Element Method (DEM) and the Lattice Boltzmann Method (LBM) for the representation of the solid and uid phases, respectively. The implementation of DEM follows a standard molecular dynamics approach and the interaction among grains are regulated by unilteral frictional visco-elastic and breakable visco-elastic bonds, in order to take into account a slightly cohesive soil behaviour. The LBM was implemented according to the Multiple Relaxation Time (MRT) scheme along with an interpolated non-slip conditions for moving boundaries, in order to improve the numerical stability of the calculations. The coupling scheme is described along with the criteria for the numerical parameters of the two methods. A representative specimen of a granular soil located at the front of an erosion pipe is first assembled by a \dry" preparation precedure and then tested under fully-saturated conditions and increasing hydraulic load over time. Backward erosion is takes place in the form of clusters of grain being eroded at the erosion front after a degradation of the material due to the breakage of tensile bonds. The other interesting feature that was observed is the creation of arches of compressive force chains. These arches enabled the specimen to maintain a stable or metastable configuration under the increasing hydraulic load
Than, Vinh-Du. "Comportement en compression des matériaux granulaires humides lâches : expérience et simulation numérique discrète." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1204/document.
An approach combining the Discrete Element Method (DEM) and experimental techniques (oedometric compression test and X-ray Computed Tomography (XRCT)) is proposed to observe the mechanical behavior of wet granular material, modeled as frictional spherical glass beads, in very loose state under growing of applied external force. An experimental observation combining one-dimensional compression test and XRCT is first presented. The plastic responses of real material (spherical glass beads) are depicted with different values of very low initial densities. The grain-scale behavior of this material is then characterized by using the XRCT and in-situ compaction test. We propose a method to detect the spherical structures from the 3D tomography images. Microstructure properties of the loose system are then analyzed and computed from the detected spherical structures. This simplified material gives further a better understanding of the macroscale behavior of wet granular soils based on their microstructure characterization. The DEM simulation then allowed us to predict accurately in 3D the plastic response of very loose assemblies of modeled wet beads to an isotropic/ oedometric compression in the presence of a small amount of an interstitial liquid, which gives rise to capillary menisci and attractive forces. The plastic responses along the compression curves are then shown in particular without and with the appearance of rolling/ pivoting resistances in contacts and also the effect of size polydispersity. The evaluation of microstructure and force transmission along the compression curve is also characterized. Finally, we compare the predictions of the experimental results with the DEM simulations results. Our comparisons show that the predictions of experiments are underestimated for the DEM simulations. Nevertheless, the combined approach in this work also provides an comprehensive characterization of the plastic and grain-scale compression behavior of wet granular soil at very loose state
Dugelas, Loic. "Stratégies probabilistes appliquées à la modélisation numérique discrète : le cas des filets pare-pierres." Thesis, Université Grenoble Alpes, 2020. https://tel.archives-ouvertes.fr/tel-02498238.
This research aims at developing numerical tools to help the design of flexible fences against rockfall.Models based on the Discrete Element Method (DEM) are developed for two flexible fences, using modeling approaches taken from the literature. The main difference between the two flexible fences investigated is their interception structure: ring net or ELITE net. For the ring net flexible fence, the DEM model proved to be a sufficient compromise between relevance, accuracy, and efficiency. On the other side, for the flexible fence with a ELITE net, new numerical developments are necessary to reach such compromise.In order to get an efficient DEM model for the ELITE flexible fence, the sliding between the cables of the net has to be taken into account. Two approaches are proposed to integrate this sliding. In the first approach, the sliding is considered without friction between the cables, while in the second approach the friction is considered. However, the calculation duration obtained with the second approach was too important to integrate it into a complete fence model.The developed models have been integrated into a design assistance tool for flexible fences, based on surrogate modeling. Parametric and sensitivity analysis are carried out with this tool, and the optimal configurations of the fence are identified
Boltcheva, Dobrina. "Modélisation géométrique et topologique des images discrètes." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. https://publication-theses.unistra.fr/public/theses_doctorat/2007/BOLTCHEVA_Dobrina_2007.pdf.
The subject of this thesis is the reconstruction of geometrical meshes from three-dimensional images for visualisation and scientific computation purposes. We introduce a new approach to handle surface reconstruction from 3D discrete data which combines techniques from both, algorithmic geometry and digital topology. The key idea is to join together two concepts: the Delaunay triangulation and the digital surfaces. Our approach allows to reconstruct triangular meshe(s) from discrete data either as a single object for a binary image, or as several objects simultaneously for a multi-labelled segmented image. We introduce two reconstruction methods which use different digital surface definitions: the first method uses a set of voxels as object boundary whereas the second is based on a combinatorial intervoxel boundary
Sakami, Siham. "Modélisation numérique des structures composites multicouches à l’aide d’une approche discrète au sens de Mindlin. Le modèle DDM (Displacement Discrete Mindlin)." Reims, 2008. http://theses.univ-reims.fr/exl-doc/GED00000982.pdf.
The present work of the thesis deals with the theoretical formulation and the evaluation of a new first order finite element for multilayered/sandwich plates and shells. It’s based on a displacement variational model that we consider as discrete, insofar as we introduce kinematic and mechanical hypothesises in a discrete manner. This model, labelled DDM (Discrete Displacement Mindlin), leads to a finite element which is geometrically simple (4 node) and efficient, owing to the linearity of bending curvatures obtained from a quadratic approximation of the normal rotations to the plate mid-surface. The new element takes into account the transverse shear effects along thickness direction and gives thin plate results when the ratio L/h (Length/ thickness) becomes big. It has been successfully validated across some known testing problems, from thin to thick laminated and sandwich
Coulibaly, Jibril. "Modélisation numérique discrète du comportement mécanique sous impact des structures d'écrans de filets pare-pierres." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI040/document.
This thesis introduces a generic model of rockfall barriers under impact loading. The structures are described as an abstract assembly of their main components. The developed model thereby enables the consideration of most of the existing technologies. A C++ code based on the Discrete Element Method is developed in order to perform the numerical simulations of impacts. The generic description of the barriers is implemented at the code level using a corresponding data structure and object-oriented programming. The generic model is completed by the mechanical models of two components. First, a mechanical model of 4-contact interlaced ring nets is developed. An experimental campaign is carried out to calibrate and validate the model against steel wire rings used in rockfall restraining nets. Second, a general sliding cable model is developed to account for the curtain effect. This model demonstrates great capabilities in describing sliding phenomena and a low computational cost. Finally, full-scale impact tests performed on two barriers of different technologies are used to validate the generic model. Numerical simulations of the full-scale tests highlight the relevance of the developed model. Numerical results agree finely with experiments and the model exhibits compelling predictive capacities for engineering applications. Deformations, loading time and forces magnitude are all predicted within 10 % relative error. Complex and unprecedented simulations of repeated impacts are carried out and the model is able to reproduce the barrier behavior both during the impact phase and after springback
Lachihab, Adel. "Un modèle numérique pour les composites biphasés matrice - inclusions rigides : Application à la détermination des propriétés élastiques et en fatigue des enrobés bitumeux." Marne-la-vallée, ENPC, 2004. http://www.theses.fr/2004ENPC0025.
Ikezouhene, Yaghkob. "Analyse numérique discrète de l'aléa fontis et du foisonnement associés aux cavités souterraines." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1109/document.
Over time, the underground cavities are subjected to aging and several types of degradation can occur. The old underground cavities have probably not been designed to be stable over the long term. They have sometimes been totally or partially backfilled, but not in a systematic way. The collapse of a mine causes deconsolidation of the upper levels of the overburden. These mechanisms can cause two types of disorders on the surface: subsidence or sinkhole. Subsidence and sinkhole can cause severe damage to structures and infrastructures in surface, but also jeopardize the safety of the population.The work of this thesis revolves around the study of rock's bulking, sinkhole and its spread in the overburden. The aims of this thesis are twofold: firstly, to study the bulking of rock during the roofs mine collapse; Secondly, modeling the spread of the sinkhole in the overburden and thus to prioritize the parameters associated with this phenomenon.The first part of this thesis is a bibliographical study which summarizes the methods of exploitation, methods of analysis of stability of underground quarries, methods of prediction of the height of collapse and estimation of the bulking factor. At the end of this bibliographic synthesis, the study focused on shallow underground quarries operated by rooms and pillars. Thus, numerical modeling using the discrete element method (MED) was chosen to analyze the instability of roofs of underground quarries.The second part focuses on the development of a numerical model with the following objectives: on the one hand, the development of a Rock Mass Discretization Program (RMDP) which constitutes the preprocessor of the STTAR3D software and the development of a Code allowing calculation of the bulking factor of the rubble of collapse. On the other hand, implementation of the behavior laws on STTAR3D.The third part consists of determining, on the one hand, the physicals and mechanicals characteristics of samples taken from the quarry of the Brasserie (Paris-France), which was chosen to test the model developed. On the other hand, determining of parameters of the behavior law used for modeling the contacts, namely “” and “μ”.Finally, the last part of this work is made of numerical simulations for which the parameters of the behavior law measured experimentally have been introduced in STTAR3D. In the first numerical study, we investigate the effect of fall height, the radius of the initial opening of the sinkhole and the fracturing degree on the bulking of the rubble, as well as the effect of variation of the bulking on the collapse height and on the subsidence. In a second step, a model of the Brasserie’s mine is realized, the behavior of which is studied by numerical simulation in order to obtain the subsidence on the surface and the collapse height, which are compared with the in-situ observations
Lachihab, Adel. "Un modèle numérique pour les composites biphasés matrice-inclusions rigides: Application à la détermination des propriétés élastiques et en fatigue des enrobés bitumineux." Phd thesis, Ecole des Ponts ParisTech, 2004. http://pastel.archives-ouvertes.fr/pastel-00001036.
Debry, Edouard. "Modélisation et simulation numérique de la dynamique des aérosols atmosphériques." Phd thesis, Ecole des Ponts ParisTech, 2004. http://pastel.archives-ouvertes.fr/pastel-00001030.
Koutsawa, Yao. "Modélisation et conception multi-échelles des matériaux : de la description atomique discrète aux modèles du continu. Application aux propriétés amortissantes des pare-brises." Thesis, Metz, 2008. http://www.theses.fr/2008METZ030S/document.
This thesis focuses on multiscale approaches to model and design multifunctional composite materials for damping applications. The main objective is to develop a multiscale modeling framework that implements hierarchical models from atomistic level modeling to structural level modeling in order to include material creation in the design of the system as a whole. Since damping applications are of interest in this study, we explore some avenues for the design of high loss materials. So, the mean-field micromechanical model introduced by Lipinski et al. [Philosophical Magazine 86 (10), 1305-1326, 2006] is extended to include frequency dependence through the viscoelastic (VE) correspondence principle. The results indicate that with proper choice of VE material properties, it is possible to have a multiphase VE composite with a high loss modulus (good energy dissipation characteristics) for a wide range of frequencies without substantially degrading the stiffness of the composite (storage modulus). Then the slightly weakened interface micromechanical model of Qu [Mechanics of Materials, 14:269-281, 1993] is also extended to investigate imperfect interface effect on damping behavior of viscoelastic composite materials. In order to investigate the nanosize effect on damping caracteristics of nanocomposite materials, we develop and validate an atomistic-continuum interface model for effective properties of elastic composite materials containing ellipsoidal nano-inhomogeneities. This approach bridges the gap between discrete systems (atomic level interactions) and continuum mechanics. An advantage of this approach is that it is developed from earlier models that consider inhomogeneities shape, thereby enabling both the nano-inhomogeneities shape and the nano-interphase shape to be simultaneously accounted for in computing the overall composite stiffness with any case of material and surface/interface anisotropies. On structural level modeling, we developed an analytical tool to study the static behavior of laminated glass beams with silicone material at ends. Then two sandwich finite elements have been developed to study static and modal behavior of viscoelastic sandwich beams and plates with complex boundaries conditions. Based on automatic differentiation and asymptotic numerical method, we developed the Diamant MATLAB toolbox which is a powerful tool to investigate many nonlinear problems namely complex non linear eigenvalue problem. Using all theses numerical tools, we investigate the effects of the materials microstructures on the modal and acoustic properties of the automotives windshields. To finish, this work shows a simple example to conceive the windshield materials microstructures to fulfill four design requirements of the whole windshield structure in service by solving a multi-objectives
Trabelsi, Brahim. "Simulation numérique de l’écoulement et mélange granulaires par des éléments discrets ellipsoïdaux." Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/9300/1/trabelsi.pdf.
Tran, Quoc Anh. "Modélisation numérique du comportement des milieux granulaires à partir de signaux pénétrométriques : approche micromécanique par la méthode des éléments discrets." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22561/document.
In the field of in situ mechanical characterization of soils, penetration tests are commonly used. Penetration tests measure the properties of soils in the domain of large deformations. The tip resistances, deduced from pile driving theory, can be measured either in dynamic conditions (q d ) either in static conditions (q c ). Recently, the measurement technique in dynamic conditions has been improved and it is now possible to record the whole response of the soil during one impact in terms of tip force and penetration distance. The exploitation of this new curve provides information not only on dynamic tip resistance but also on additional mechanical parameters involved during the driving of the tip. The objective of this work is to develop a numerical model in 2D able to reproduce the penetrometric record obtained experimentally by static or dynamic penetration tests. This model is based on the discrete element method with a simple linear contact model. After the validation of the model, a parametric study was performed essentially on the loading type (static or dynamic), the penetration rate, the particle size of the granular material and the arrangement (density variation). Besides the influence of these parameters on the penetrometer signals and the tip resistance, a particular attention was focused on micromechanical analysis: energy dissipation in the medium, force chain evolution, contact orientation. This analysis requires the development of specific numerical tools to better understand the penetration mechanism and try to explain the macroscopic mechanical response obtained. The penetration rate influences significantly only in the dense flow regime on the static and dynamic penetration tests. There is no significant microscopic difference between static and dynamic penetration tests with similar penetration rates. Regarding the influence of the characteristics of the material, the numerical results obtained conform to the real results when the particle friction or the compactness of the medium varies. Concerning the particle size, the dynamic signal variation and the dynamic tip force increases when the average particle diameter increases
Liu, Hua. "Nouveau procédé d'enrobage de particules en voie sèche et modélisation numérique : préparation de catalyseur solide propre pour la méthanisation." Electronic Thesis or Diss., Centrale Lille Institut, 2021. http://www.theses.fr/2021CLIL0016.
The objective of this thesis is to propose a new methodology – dry particle coating technique to prepare catalyst supports for the methanation reaction. Dry particlecoating is considered as an environmentally friendly and low-cost technique. However, it is crucial to understand the mechanism of the dry coating process, the factorsaffect the coating performance, the evaluation of the coating quality, the large-scale production as well as the exploration of new application fields.In this work, the method of preparing new catalyst supports is to coat γ-Al2O3 and 316L steel (S.S316L) particles with TiO2, SiO2, and Zeolite nanoparticles. However,these powders (TiO2, SiO2, and Zeolite) are highly cohesive and form agglomerates of uncontrollable sizes, the nanoscale of the powders poses a major problem inthe accuracy of size measurements. The coating process requires analysis of the nanoparticles. Four analytical techniques were applied and compared. The basicprinciple of the dry particle coating process is the mixing of particles under mechanical force (impact/compression/shear force). Host particle: γ-Al2O3 and S.S316Lhave an average diameter of about 67 μm and 98.3 μm will be used as host particles to prepare new carriers. The guest particles: TiO2, SiO2 and Zeolite with nanosizewill be used to coat the surface of γ-Al2O3 and S.S316L to prepare the new substrates (such as TiO2/S.S316L, SiO2/S.S316L, Zeolite/S.S316L and TiO2/γ-Al2O3,SiO2/γ-Al2O3, Zeolite/γ-Al2O3,). The coating of particles in dry process is due to mechanical/shear forces and it depends on collisions, particle movements, interactionsbetween particles and the impact of operating conditions (the rotation speed and coating time) in the mixer. A numerical modeling DEM (Discrete Element Method)has been implemented to answer and explain the phenomena and the coating process.The results of the analysis of the nanoparticles showed that the technique of diffraction/laser scattering (LD) highlights a larger size of particle of the nanopowder(overestimation) on the other hand the dynamic diffusion of the light (DLS) shows a smaller size. Transmission electron microscopy (TEM) indicates the smallerdiameter of the nanopowder. The coating results highlight a good coating by SiO2, TiO2, and Zeolite nanoparticles on the surface of γ-Al2O3 and S.S316L under 3500rpm and 5 min. However, for the same guest particles with different host particles, the S.S316L coating shows excellent coating. Numerical modeling reveals that themain factors affecting the simulation are: rotational speed and particle size. Simulation of the coating indicates that the interfacial energy between the host and theguest is the main parameter affecting the coating
Rastiello, Giuseppe. "Influence de la fissuration sur le transfert de fluides dans les structures en béton : stratégies de modélisation probabiliste et étude expérimentale." Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00861375.
Taforel, Paul. "Apport de la Méthode des Éléments Discrets à la Modélisation des Maçonneries en Contexte Sismique : Vers une Nouvelle Approche de la Vulnérabilité Sismique." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2012. http://tel.archives-ouvertes.fr/tel-00801814.
Al-Hout, Julie. "Etudes expérimentales et numériques du comportement des structures en Pisé et en maçonnerie : Apport de la MED." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI079/document.
This contribution, based on experimental work and numerical modeling using the distinct elements method, aims to study masonry structures and rammed earth structures. For the masonry part, our study first deals with reduced models tested on tilting table, then in a second time we tested brick walls on a representative scale. In the second part, we conducted tests on rammed earth walls under a shear loading, with or without axial prestressing of the containment which corresponds to a descent of load. Numerical modeling using the discrete element method has been carried out for these different case studies. The comparison between the experimental and numerical results, allowed us to evaluate the relevance and limits of modeling via the discrete element method (DEM)
Barbier, Carine. "Modélisation numérique du comportement mécanique de systèmes enchevêtrés." Grenoble INPG, 2008. http://www.theses.fr/2008INPG0159.
We employ a discrete simulation adapted from molecular dynamics techniques in order to study the mechanics of entangled semiflexible fibers. Each fiber is discretized by a small number of segments allowed to stretch and bend. A few hundred fibers, initially straight and placed and oriented at random are simulated during incremental compressions in the three directions of space or incremental shear. This model can take into account geometrical parameters (volume fraction, aspect ratio, orientation distribution. . . ) as well as “material” parameters (flexibility, nature of contacts. . . ). This model is also employed to generate samples used to validate image analysis techniques
Bargui, Henda. "Modélisation des comportements mécaniques et hydrauliques de massifs rocheux simulés par des assemblages de blocs rigides : Introduction d'un couplage hydro-mécanique." Phd thesis, Marne-la-vallée, ENPC, 1997. http://www.theses.fr/1997ENPC9705.
This research aims at modelling the hydro-mechanical behaviour of fissured rock masses by improvement and extension of a discrete element model, called BRIG3D. This model simulates fissured rock mass as a set of rigid blocks interacting along their interfaces. Interface deformation is related to the relative displacement of the corresponding blocks. Being subject to external loads, the total set of blocks moves until equilibrium is reached. The computation of this equilibrium has been improved by redefining the model description of the rigid block movement, the interface position and the stress distribution along an interface. To describe flow problems through blocks interfaces, a boundary element model has been developed. Flow through each interface is assumed to be laminar, stationary and planar. This hydraulic model has then been coupled with the mechanical model BRIG3D and used to analyse hydro-mechanical rock mass behaviour under varying loads ; In particulard, a study of a dam foundation has been carried out
Cadile, Claudia. "Modélisation DEM et approche expérimentale de la dynamique d'un système réactif en lit fluidisé dense : application à la gazéification de la biomasse." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4769/document.
Energy production from green and renewable resources, such as biomass, are currently experiencinga significant growth. Thermochemical conversion of this biomass by gasification is a process usedfor over a century but still requires significant developments in terms of rentability optimizationand quality improvement of products gases.The work carried out in collaboration between the CNIM company and the IUSTI laboratoryallowed the establishment of a numerical simulation tool to study locally different coupled phenomenaoccurring in a dense fluidized bed gasification reactor. The chosen approach, DEM (DiscreteElement Method), is based on the monitoring of particle packets. The simulation results werecompared to experimental measurements realised in IUSTI and LERMAB laboratories : measuringpressure in a shallow fluidized bed and characterization of pyrolysis reaction with the timetracking of particle density by an innovative method, temperature and the composition of theproducts gases. On a larger scale, the numerical code predictions were compared with velocity,particles mixing and segregation profiles from experimental measurements of the literature. Theobtained numerical results of bi-solid fluidized bed with and without chemical reactions are ingood agreement with the experimental measurements. It helped to highlight the strong couplingbetween hydrodynamic and thermochemical phenomena.This work opens up new perspectives on the experimental plan and numerical simulation whichDEM approach has shown great potential. The extrapolation of the DEM model for the simulationof gasification industrial reactors remains a challenge in terms of computer resources
Bargui, Henda. "Modélisation des comportements mécaniques et hydrauliques de massifs rocheux simulés par des assemblages de blocs rigides : Introduction d'un couplage hydro-mécanique." Phd thesis, Ecole Nationale des Ponts et Chaussées, 1997. http://tel.archives-ouvertes.fr/tel-00529406.
Kunhappan, Deepak. "Modélisation numérique de l’écoulement de suspensions de fibres souples en régime inertiel." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI045/document.
A numerical model describing the behavior of flexible fibers under inertial flows was developed by coupling a discrete element solver with a finite volume solver.Each fiber is discretized into several beam segments, such that the fiber can bend, twist and rotate. The equations of the fiber motion were solved usinga second order accurate explicit scheme (space and time). The three dimensional Navier-Stokes equations describing the motion of the fluid phase was discretizedusing a fourth th order accurate (space and time) unstructured finite volume scheme. The coupling between the discrete fiber phase and the continuous fluid phasewas obtained by a pseudo immersed boundary method as the hydrodynamic force on the fiber segments were calculated based on analytical expressions.Several hydrodynamic force models were analyzed and their validity and short-comings were identified. For Reynolds numbers (Re) at the inertial regime(0.01 < Re < 100, Re defined at the fiber scale), non linear drag force formulations based on the flow past an infinite cylinder was used. For rigid fibers in creeping flow, the drag force formulation from the slender body theory was used. A per unit length hydrodynamic torque model for the fibers was derived from explicit numerical simulations of shear flow past a high aspect ratio cylinder. The developed model was validated against several experimental studies and analytical theories ranging from the creeping flow regime (for rigid fibers) to inertial regimes. In the creeping flow regime, numerical simulations of semi dilute rigid fiber suspensions in shear were performed.The developed model wasable to capture the fiber-fiber hydrodynamic and non-hydrodynamic interactions. The elasto-hydrodynamic interactions at finite Reynolds was validated with against two test cases. In the first test case, the deflection of the free end of a fiber in an uniform flow field was obtained numerically and the results were validated. In the second test case the conformation of long flexible fibers in homogeneous isotropic turbulence was obtained numerically and the results were compared with previous experiments. Two numerical studies were performed to verify the effects of the suspended fibers on carrier phase turbulence and the numerical model was able to reproduce the damping/enhancement phenomena of turbulence in channel and pipe flows as a consequence of the micro-structural evolution of the fibers
Lajevardi, Seyed Hamid. "Comportement des géosynthétiques en ancrage : Modélisation physique et numérique." Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00995109.
Ghaouti, Abdelwahab. "Modélisation numérique des matériaux granulaires à interactions à distance." Ecully, Ecole centrale de Lyon, 1995. http://bibli.ec-lyon.fr/exl-doc/TH_T1641_aghaouti.pdf.
The numerical simulation of the behaviour of granular materials interacting at large scale, using the TRUBAL software of Peter Cundall, is the topic of this thesis. This software is described by recalling the principle of the Discrete Element Method (D. E. M. ) and the particularity of TRUBAL. In this method, particles motion is described by integration of motion equations and contact forces are calculated by using an appropriate contact law. The theoretical approach developed at "Ecole Centrale de Lyon" that lies the global behaviour of a granular material to its local behaviour is then presented : the statistical homogenisation approach. The first medium studied is the soap bubbles medium for which many experiments made at "Laboratoire de Tribologie et Dynamique des Systemes" of the "Ecole Centrale de Lyon" help us to fixe the modelling. The interaction law between soap bubbles is formed by an attractive part at large scale, which requires modifications of the Trubal software, and a linear elastic part at short scale. Homogeneous tests showed that the simulated behaviour is representative of the behaviour generally observed. The effect of the set of attractive forces is described by using a cohesive stress tensor which was defined by homogenisation. The expression of the tensor is obtained by using a radial distribution function. The homogenisation approach allowed to define the global behaviour of the medium from the local contact law : numerical tests are in good agreement with the theory. Two non-homogeneous tests showed the ability to use the Trubal software to simulate Tribological problems on interfaces: the indentation test of a thin half layer with a crystalline punch and the alternate shearing (friction and wear) of an amorphous layer (third body). The second medium studied is a granular material with capillary forces. The modelling of the capillary forces by the Laplace-Young relation allowed to carry out homogeneous and non-homogeneous tests. A non-confined triaxial test showed the influence on the behaviour of the water presence in the medium. Otherwise the influence is negligible under an important confinement. Non-homogeneous tests concern bidimensionnal flows in silos in different conditions: capillary cohesion (moisture content) or not, the outlet width ant the angle of the walls. The formation of arches is particularly studied as well as the stress distribution on the walls. The set of this results show the advantage of the Discrete Element Method to analyse the behaviour of granular materials interacting at large scale
Pacheco-Martínez, Ana María. "Extracting cell complexes from 4-dimensional digital images." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2262/document.
A digital image can be defined as a set of n-xels on a grid made up by n-cubes. Segmentation consists in computing a partition of an image into regions. The n-xels having similar characteristics (color, intensity, etc.) are regrouped. Schematically, each n-xel is assigned a label, and each region of the image is made up by n-xels with the same label. The methods "type" Marching cubes and Kenmochi et al. construct complexes representing the topology of the region of interest of a 3-dimensional binary digital image. In the first method, the algorithm constructs a simplicial complex, whose 0-cells are points of the edges of the dual grid. Inthe second one, the authors construct a cell complex on a dual grid, i.e. the 0-cells of the complex are vertices of the dual grid. In order to construct the complex, Kenmochi et al. compute (up to rotations) the different configurations of white and black vertices of a cube, and then, they construct the convex hulls of the black points of these configurations. These convex hulls define the cells of the complex, up to rotations. The work developed in this thesis extends Kenmochi et al. method todimension 4. The goal is to construct a cell complex from a binary digital image defined on a dual grid. First, we compute the different configurations of white and black vertices of a 4-cube, up to isometries, and then, we construct the convex hulls defined by these configurations. These convex hulls are constructed by deforming the original 4-cube, and we distinguishseveral basic construction operations (deformation, degeneracy of cells, etc.). Finally, we construct the cell complex corresponding to the dual image by assembling the cells so o
Una imagen digital puede ser definida como un conjunto de n–xeles en un mallado constituido de n–cubos. Los n–xeles pueden ser identificados con: (1) los n–cubos del mallado, o con (2) los puntos centrales de estos n–cubos. En el primer caso, trabajamos con un mallado primal, mientras que en el segundo, trabajamos con un mallado dual construido a partir del mallado primal. La segmentación consiste en calcular una partición de una imagen en regiones. Los n–xeles que tienen características similares (color, intensidad, etc.) son reagrupados. Esquemáticamente, a cada n–xel se le asocia una etiqueta, y cada región de la imagen está constituida de n–xeles con la misma etiqueta. En particular, si las únicas etiquetas permitidas para los n–xeles son “blanca” y “negra”, la segmentación se dice binaria: los n–xeles negros forman el primer plano (foreground) o región de interés en cuestión de análisis de la imagen, y los n–xeles blancos forman el fondo (background). Ciertos modelos, como los Grafos de Adyacencia de Regiones (RAGs), los Grafos Duales (DGs) y la carta topológica, han sido propuestos para representar las particiones en regiones, y en particular para representar la topología de estas regiones, es decir las relaciones de incidencia y/o adyacencia entre las diferentes regiones. El RAG [27] es un precursor de este tipo de modelos, y ha sido una fuente de inspiración de los DGs [18] y de la carta topológica [9, 10]. Un RAG representa una imagen primal etiquetada por un grafo: los vértices del grafo corresponden a regiones de la imagen, y las aristas del grafo representan las relaciones de adyacencia entre la regiones. Los DGs son un modelo que permite resolver ciertos inconvenientes de los RAGs para representar imágenes de dimensión 2. La carta topológica es una extensión de los modelos anteriores definida para manipular imágenes primales de dimensión 2 y 3, representando no solamente las relaciones topológicas, sino también las relaciones geométricas
Oetomo, James. "Comportement des murs de soutènement en pierre sèche : une modélisation par approche discrète." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0025/document.
A dry-Stone retaining wall (DSRW) is a vernacular structure constructed by stacking the stone blocks without using any binder. In the past, this wall has been extensively used, shaping the French countryside area, built either for road or railroad retaining wall. However, the use of this technology has disappeared during 20th century, due to the emergence of more industrialized materials such as reinforced concrete. Confronted by these ageing heritage structures, it is very difficult to propose a proper reparation procedure since the building codes associated with this structure are nonexistent. For the same reason, though this technology perfectly answers the questions raised by the concept of sustainable development, in practice this structure is rarely considered or used by the engineering advisors. The failure of the newly built DSRWs can be attributed to the following reasons: (1) an excessive pressure of backfill retained by the wall, (2) a presence of an excessive concentrated load on the backfill surface, close to the top part of the wall. These two types of loading lead to two very different types of failure, respectively: (1) plane strain failure, (2) bulging failure. Three recent experimental campaigns of DSRWs loaded with: (1) hydrostatic pressure, (2) backfill, (3) backfill with a concentrated on its surface, provided a better understanding of phenomena involved in these failures. The work presented in this PhD thesis contributes to the development of new scientific tools capable to help design the DSRWs, as well as validating existing tools. The recent full-Scale experimental campaign will serve as a basis to the validation of the developed numerical tools. We have chosen to use a discrete element method (DEM) where each stone block of the wall is modeled individually, complying with the nature of real DSRW. In the first place, the plane strain failure is modeled by a purely discrete approach and a discrete-Continuum approach. The advantage and inconvenient of each method will be presented in advance. A quantitative validation of numerical models is provided by comparing the critical height of loading with results derived from the full-Scale experimental campaign. Thereafter, a 3D qualitative model of DSRWs loaded with a concentrated load on the backfill surface is presented. The modeling problem is noted and the influence of the block form in regards of the related failure mechanism is studied
Vernet, Raphaël. "Approche mixte théorie / expérimentation pour la modélisation numérique de chambres réverbérantes à brassage de modes." Phd thesis, Clermont-Ferrand 2, 2006. https://theses.hal.science/docs/00/69/11/24/PDF/2006CLF21654.pdf.
Vernet, Raphaël. "Approche mixte théorie / expérimentation pour la modélisation numérique de chambres réverbérantes à brassage de modes." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2006. http://tel.archives-ouvertes.fr/tel-00691124.
Mutabaruka, Patrick. "Modélisation numérique des milieux granulaires immergés : initiation et propagation des avalanches dans un fluide." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-00984870.
Catalano, Emanuele. "Modélisation physique et numérique de la micro-mécanique des milieux granulaires saturés. Application à la stabilité de substrats sédimentaires en génie cotier." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENU012/document.
The behaviour of multiphase materials covers a wide range of phenomena of interest to both scientists and engineers. The mechanical properties of these materials originate from all component phases, their distribution and interaction. A new coupled hydromechanical model is presented in this work, to be applied to the analysis of the hydrodynamics of saturated granular media. The model associates the discrete element method (DEM) for the solid phase, and a pore-scale finite volume (PFV) formulation of the flow problem. The emphasis of this model is, on one hand, the microscopic description of the interaction between phases, with the determination of the forces applied on solid particles by the fluid; on the other hand, the model involve affordable computational costs, that allow the simulation of thousands of particles in three dimensional models. The medium is assumed to be saturated of an incompressible fluid. Pore bodies and their connections are defined locally through a regular triangulation of the packings. The analogy of the DEM-PFV model and the classic Biot's theory of poroelasticity is discussed. The model is validated through comparison of the numerical result of a soil consolidation problem with the Terzaghi's analytical solution. An approach to analyze the hydrodynamic of a granular sediment is finally presented. The reproduction of the phenomenon of soil liquefaction is analysed and discussed
Archoun, Mohamed. "Modélisation prétopologique de la segmentation par croissance de régions des images à niveaux de gris." Lyon 1, 1993. http://www.theses.fr/1993LYO10155.
Lakhlili, Jalal. "Modélisation et simulation numériques de l'érosion par méthode DDFV." Thesis, Toulon, 2015. http://www.theses.fr/2015TOUL0013/document.
This study focuses on the numerical modelling of the interfacial erosion occurring at a cohesive soil undergoing an incompressible flow process. The model assumes that the erosion velocity is driven by a fluid shear stress at the water/soil interface. The numerical modelling is based on the eulerian approach: a penalization procedure is used to compute Navier-Stokes equations around soil obstacle, with a fictitious domain method, in order to avoid body- fitted unstructured meshes. The water/soil interface’s evolution is described by a Level Set function coupled to a threshold erosion law.Because we use adaptive mesh refinement, we develop a Discrete Duality Finite Volume scheme (DDFV), which allows non-conforming and non-structured meshes. The penalization method, used to take into account a free velocity in the soil with non-body-fitted mesh, introduces an inaccurate shear stress at the interface. We propose two approaches to compute accurately the erosion velocity of this free boundary problem. The ability of the model to predict the interfacial erosion of soils is confirmed by presenting several simulations that provide better evaluation and comprehension of erosion phenomena
Salot, Christophe. "Modélisation du comportement mécanique d'un matériau granulaire composite par la méthode des éléments discrets." Phd thesis, Université Joseph Fourier (Grenoble), 2007. http://tel.archives-ouvertes.fr/tel-00203393.
Le modèle repose sur l'utilisation d'éléments discrets de formes simples non convexes et sur une procédure de calibration des paramètres. Il a été validé par des essais expérimentaux réalisés pour diverses densités sur des matériaux granulaires homogènes. Le modèle est appliqué aux mélanges sable – gravier et sable – pastilles de pneu pour diverses proportions et comparé à des résultats expérimentaux. L'influence de la forme et de la taille relative des éléments est discutée.
Rousseau, Jessica. "Modélisation numérique du comportement dynamique de structures sous impact sévère avec un couplage éléments discrets / éléments finis." Phd thesis, Grenoble 1, 2009. http://www.theses.fr/2009GRE10219.
That study focuses on concrete structures submitted to impact loading and is aimed at predicting local damage in the vicinity of an impact zone as well as the global response of the structure. The Discrete Element Method (DEM) seems particularly well suited in this context for modeling fractures. An identification process of DEM material parameters from macroscopic data (Young's modulus, compressive and tensile strength, fracture energy, etc. ) will first be presented for the purpose of enhancing reproducibility and reliability of the simulation results with DE samples of various sizes. Then, a particular interaction, between concrete and steel elements, was developped for the simulation of reinforced concrete. The discrete elements method was validated on quasi-static and dynamic tests carried out on small samples of concrete and reinforced concrete. Finally, discret elements were used to simulate impacts on reinforced concrete slabs in order to confront the results with experimental tests. The modeling of a large structure by means of DEM may lead to prohibitive computation times. A refined discretization becomes required in the vicinity of the impact, while the structure may be modeled using a coarse FE mesh further from the impact area, where the material behaves elastically. A coupled discrete-finite element approach is thus proposed: the impact zone is modeled by means of DE and elastic FE are used on the rest of the structure. An existing method for 3D finite elements was extended to shells. This new method was then validated on many quasi-static and dynamic tests. The proposed approach is then applied to an impact on a concrete structure in order to validate the coupled method and compare computation times
Rousseau, Jessica. "Modélisation numérique du comportement dynamique de structures sous impact sévère avec un couplage éléments discrets / éléments finis." Phd thesis, Grenoble 1, 2009. http://tel.archives-ouvertes.fr/tel-00411870.
L'application de la méthode des éléments discrets sur des structures de grandes dimensions est limitée par le nombre d'éléments discrets nécessaires. Pour garder la qualité de prédiction locale et rendre cette méthode adaptée à l'échelle d'une structure, celle-ci est couplée à la méthode des éléments finis dans les parties qui ne sont pas soumises à d'importantes discontinuités. Cette approche couplée permet des gains de temps importants, tant pour la modélisation que la pour la simulation.
Une partie importante de cette thèse concerne le développement et la validation du modèle éléments discrets de béton armé. Ce travail propose une optimisation du processus d'identification des paramètres locaux du modèle discret afin de le rendre plus prédictif en ce qui concerne le béton. Ensuite, une liaison particulière, entre éléments discrets d'acier et de béton, a été conçue pour la simulation du béton armé. Enfin, elle a été utilisée pour la simulation d'impacts sur des dalles en béton armé afin de confronter les résultats à des essais expérimentaux.
La deuxième partie du travail de thèse traite de la méthode de couplage entre éléments discrets et éléments finis. Une méthode existante pour les éléments finis volumiques a été étendue aux éléments finis de type coque. Enfin, la méthode de couplage a été utilisée pour simuler un impact sur une structure de type enceinte de confinement.
Makke, Laurent. "Modélisation tridimensionnelle du rayonnement infrarouge atmosphérique utilisant l'approximation en émissivité : application à la formation du brouillard radiatif." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1061/document.
The Atmospheric Radiation field has seen the development of more accurate and faster methods to take into account absorption. Modelling fog formation, where Infrared Radiation is involved, requires accurate methods to compute cooling rates. Radiative fog appears with clear sky condition due to a significant cooling during the night where absorption is the dominant processus. Thanks to High Performance Computing, multi-spectral approaches of Radiative Transfer Equation resolution are often used. Nevertheless, the coupling of three-dimensional radiative transfer with fluid dynamics is very computationally expensive. Radiation increases the computation time by around fifty percent over the pure Computational Fluid Dynamics simulation. To reduce the time spent in radiation calculations, a new method using the broadband emissivity has been developed to compute an equivalent absorption coefficient (spectrally integrated). Only one resolution of Radiative Transfer Equation is needed against $N_{text{band}} times N_{text{gauss}}$ for an $N_{text{band}}$ model with $N_{text{gauss}}$ quadrature points on each band. A comparison with simulation data has been done and the new parameterization of Radiative properties shows the ability to handle variations of gases concentrations and liquid water. A dynamical study through the coupling between the infrared radiation model and Code_Saturne has been done to validate our parametrization. Finally the model was tested on a 3-D domain with idealized buildings to catch 3-D infrared radiative effects due to horizontally inhomogenities of the liquid water content field and buildings
Ngoma, Jeff. "Etude numérique et expérimentale de la déstabilisation des milieux granulaires immergés par fluidisation." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4712/document.
The subject of this thesis is the numerical analysis and experimental investigation of the destabilization of submerged granular media caused by fluidization. This hydromechanical instability is one of the mechanisms that may trigger the regressive erosion, which is one of the main degradation phenomena driving the internal erosion of earthen hydraulic constructions. Such erosion mechanisms can only be understood through a rigorous description of the coupling and interaction between the eroding fluid and the soil particles. For this purpose, a 2D model has been used coupling two different numerical techniques, namely the discrete element method (DEM) for modelling the mechanical behaviour of the solid phase and the Lattice Boltzmann method (LBM) for the fluid phase. The experimental validation of this numerical 2D simulation has been carried out using two optical techniques for the internal visualization of a granular sample, namely the adjustment of the refraction index of the two phases and the laser-induced fluorescence
Pedot, Thomas. "Modélisation du couplage thermique entre la combustion et l'encrassement des tubes d'un four de raffinerie." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0095/document.
In industrial refinery furnaces, the efficiency of the thermal transfer to heat crude oil before distillation is often altered by coke deposition inside the process pipes. This leads to increased production and maintenance costs, and requires better understanding and control. Crude oil fouling is a chemical reaction that is, at first order, thermally controlled. In such large furnaces, the predominant heat transfer process is thermal radiation by the hot combustion products, which directly heats the pipes. As radiation fluxes depend on temperature differences, the pipe surface temperature also plays an important role and needs to be predicted with sufficient accuracy. This temperature results from the energy balance between thermal radiation and conduction in the solid material of the pipe, meaning that the thermal behavior of the whole system is a coupled radiation-conduction problem. In this work, this problem is solved in a cylindrical furnace, using the Discrete Ordinate Method (DOM) with accurate spectral models for the radiation of combustion gases, described by a complex chemistry flame model, and coupled to heat conduction in the pipe to predict its wall temperature. An energy balance confirms that heat transfers are effectively dominated by thermal radiation. Good agreement with available measurements on a real furnace shows that the proposed approach is able to predict the heat transfer to the pipe. The method gives an accurate prediction of the radiative source term and temperature fields in the furnace and on the pipe surface, which are key parameters for liquid fouling inside the pipe. Although reasonably accurate results are obtained with simple models, they still can be easily improved by more sophisticated models for turbulence, combustion and radiation. The next step is to couple the calculation of the pipe temperature to a fouling law. Since exact composition of crude oil is not available, one needs to model coke deposition with simple fouling law. The idea is to model the deposition rate by a thermal resistance added to the heated pipe and allows to coupling the calculation of the pipe temperature to a fouling law. A simple chemical model is used, and validated against a labscale experiment, prior to apply it to a furnace configuration. Comparing the temperature obtained with the simulation to the temperature measured by thermal probes at selected locations shows that the simulation is able to capture the temperature variation at these points. It is shown that coking occurs when the temperature has remained high on both sides of the pipe for a sufficient length. We explain how to extract a fouling law in controlled condition when the deposit is induced by thermal stressing of the crude. Finally, the whole system, including radiation,conduction and deposition, is coupled. Results are compared to the real furnace and show relatively good agreement in terms of external skin pipe temperature prediction. This observation validates the methodology exposed in this script
Groza, Mayya. "Modélisation et discrétisation des écoulements diphasiques en milieux poreux avec réseaux de fractures discrètes." Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4093/document.
This thesis presents the work on modelling and discretisation of two-phase flows in the fractured porous media. These models couple the flow in the fractures represented as the surfaces of codimension one with the flow in the surrounding matrix. The discretisation is made in the framework of Gradient schemes which accounts for a large family of conforming and nonconforming discretizations. The test cases are motivated by the target application of the thesis concerning the gas recovery under the hydraulic fracturing process in low-permeability reservoirs
Salot, Christophe. "Modélisation du comportement mécanique d'un matériau granulaire composite par la méthode des éléments discrets." Phd thesis, Grenoble 1, 2007. http://www.theses.fr/2007GRE10243.
Composites granular materials are frequent components of geotechnical structures. They are composed of different size and nature of particles which generate a complex behaviour difficult to appreciate in experiments. A three-dimensional discrete element model and a specific procedure were developed to simulate the macroscopic behaviour of these materials under triaxial loading. The numerical model implements non convex elements and is based on a parameter calibration procedure. This approach is validated by comparison with experimental tests on homogeneous granular materials for a variety of relative densities. Simulations are applied with sand – gravel and sand – tyre chips mixtures for different mixing ratios and results are compared with experimental ones. The influence of shape and relative size of elements is discussed
Philippot, Alexandre. "Contribution au diagnostic décentralisé des systèmes à événements discrets: application aux systèmes manufacturiers." Reims, 2006. http://theses.univ-reims.fr/exl-doc/GED00000337.pdf.
Fault diagnosis of industrial systems is a subject that has received a great attention in the past few decades. It is defined as the process of detecting and isolating faults. Fault detection leads to a binary decision that either the system is working under normal conditions or an abnormality in its behaviour has occurred. Fault detection is followed by fault isolation, which determines the fault type, location and causes. This thesis presents a decentralized approach to realize the diagnosis of Discrete Event Systems (DES), particularly manufacturing systems with discrete sensors and actuators. This approach considers the plant as a set of elements. Each plant element is composed of an actuator and a set of sensors. The construction of the local diagnosers is based on a modular modelling of the plant elements, of the controller specifications and the temporal information about the actuators reactivity. It is a special case of an observer that carries fault information by means of labels attached to states. Diagnosers base their decisions on the sequences of observed events, on the current behavior and/or on the time delays between these events. In order to verify that the set of local diagnosers are capable to diagnose a set of faults within a bounded delay, a notion of codiagnosability must be defined. In this thesis, a timed-event-state-based diagnosability notion is defined in order to verify the diagnosability property of the set of local diagnosers. All local diagnosis decisions must be merged in order to obtain one global diagnosis decision. This fusion can be realized by a coordinator based on a set of rules. The goal of this coordinator is to solve the problem of decision conflict and/or ambiguity among local diagnosers in order to obtain a diagnosis performance equivalent to the one of the centralized diagnoser. Two examples of manufacturing applications are used to illustrate and to show the advantages and the interest of this approach. A simulation tool based on Stateflow of Matlab is constructed in order to test and validate the proposed approach on application examples
Liu, Xuemei. "Conception en voie sèche de catalyseurs propres Co/Al2O3 pour la synthèse Fischer-Tropsch et modélisation numérique DEM." Thesis, Ecole centrale de Lille, 2018. http://www.theses.fr/2018ECLI0013.
This thesis concerns the application of a novel preparation technology for Co/Al2O3 clean catalysts applied in Fischer Tropsch (FT) synthesis. The catalysts were prepared using a dry coating process in a high shear mixer “Picomix”. The operating conditions, alumina supports, cobalt crystallite size and cobalt loading content were optimized to increase the catalytic activity of Co/Al2O3 catalysts. Besides, DEM modeling was performed to describe the behavior or powders in the mixer. Experimental results showed a very good adhesion of the nano Co3O4 particles on the surface of Al2O3 particles after processed in the mixer under a high rotational speed and a short time. The heat-treated Al2O3γ particles presented enhanced mechanical strength of catalysts, however, exhibited relatively low catalytic activity. The Co3O4 crystallite size decreased from 64 nm to 11 nm after milling in planetary ball mill under 600 rpm for 40 h. Finally, the optimal catalyst was prepared by mixing milled-Co3O4 and Al2O3γ particles in “Picomix” under 5000 rpm for 5 min with 5 wt.% of Co. The obtained catalyst presented high CO conversion (37 %), high C5+ hydrocarbons selectivity (75 %) and low CH4 selectivity (13 %) in FT synthesis reaction at 250 oC. The DEM mumerical modeling revealed that the parameters related to operating condition, device geometry, and particle intrinsic properties had an impact on particle behavior and coating quality of materials
Nader, François. "Modélisation de la rupture 3D des grains polyédriques par éléments discrets." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI082/document.
Rockfill structures are very popular among civil engineering structures (dams, retaining walls, . . . ). Important settlements can take place during the lifetime of these structures, settlements mainly caused by the breakage of rockfill grains. This thesis proposes a numerical model that allows the simulation of the behavior of granular materials exhibiting grain breakage. To take into account the discrete nature of these media, the discrete element method is chosen. The adopted strategy is the Non-Smooth Contact Dynamics method, where grains are considered to be rigid. To generate blocks having complex shapes, a 3D grain model is suggested. This grain model is then discretized into tetrahedral subgrains, joined together using cohesive bonds so that breakage can be simulated. A Mohr-Coulomb failure criterion is used for the cohesive bonds. The model is implemented into the LMGC90 software platform. At first, the model is tested in single grain crushing simulations between two plates. Multiple parameters controling the strength of the grain are studied : the intra-granular cohesion, the size, the discretization and the orientation of the grain. The scale effect that characterizes this type of material is verified. Then the model is tested in numerical simulations of œdometric compression of rockfill. The influence of the parameters of the model and of those of the granular medium are studied. The results of œdometric simulations are compared to experimental results, and present a good agreement. Lastly, numerical experimentations are conducted in order to study the energies that are brought into play in the simulations. The surface creation energy is estimated for this type of material. Results are close to the data provided in the literature
Hosseini, Sadr Abadi Hamid. "Identificiation in-situ des sols liquéfiables par pénétromètre statique cyclique : modélisations physiques et numériques." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI078.
The identification of liquefiable soils and the behaviour of soils in response to cyclic stresses are important challenges in geotechnical engineering. Various laboratory and in-situ tests are used to evaluate this phenomenon. The Equaterre group, in particular, is developing a static penetrometer with a cyclic tip that allows a cyclic variation of the force to be imposed on the tip by means of sliding central rods and the resulting deformations to be measured. This provides direct access to the response of the soil in place, and potentially highlights a tendency towards liquefaction or cyclic mobility. This thesis has two main parts: physical modeling in a calibration chamber and numerical modeling.Physical modelling consists in carrying out feasibility tests of the method developed by Equaterre in a calibration chamber in the 3SR Grenoble laboratory. The tests in the calibration chamber were carried out on Fontainebleau sand, with two states of medium density and loose. CPTU tests and Equaterre cyclic penetrometer were performed in both situations. The results showed the good potential of this method to identify the risk of liquefaction.Numerical modelling is based on a coupling between the discrete element method (DEM) for the solid phase and a finite volume method defined at pore scale (PFV method) for internal flow. The geometry of revolution is used to reduce the modelled domain to a quarter of the problem, and a gradation of particle sizes according to the distance to the tip is also implemented to reduce the total number of particles (and therefore the computation times) while maintaining a fine discretization in the immediate vicinity of the tip. Two types of materials, dense and loose, are simulated and for each one the mechanical response is analyzed for the dry case and for the saturated case, under monotonous and cyclic loading. The analysis of the responses in terms of force and interstitial pressure shows a good qualitative agreement with the results in the calibration chamber.Keywords: Static cyclic penetrometer; Calibration chamber; Soil liquefaction; Discrete element method (DEM); Pore-scale finite volume method (PFV)
Ben, Turkia Salma. "Etude expérimentale et numérique du comportement mécanique des matériaux granulaires : De la simulation discrète d'essais de laboratoire à la mise en place d'une procédure de calibration des paramètres d'entrée." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0004.
The processing, transport, handling and storage of granular materials underlies the operations of numerous industries. Thus, reliably predicting the dynamics of granular materials is critical for successful process operation and sensible process optimization. Granular materials are complex systems that can display solid, liquid and gas phases that are often characterized by nonfrivolous transitions between static, quasi-static and dynamic states. Needless to say, the manifestation of segregation, arching and jamming can have dire consequences for manufacturers. Predicting the bulk behavior of granular media requires a good understanding of the dominant mechanisms involved at grain or particle level. It is therefore essential to numerically simulate at the grain or particle scale to accurately predict granular dynamics over all regimes. In the discrete element method (DEM) there are constitutive models that describe the material responses for different mechanical loading conditions. However, significant computational resources are required to simulate large number of particles often making bulk and industrial scale simulations intractable.In this study, we use the BlazeDEM3D-GPU simulation framework that uses GPU (Graphic Processing Unit) compute, allowing DEM simulations to be conducted tens to hundreds times faster. This tremendous increases in compute efficiency creates new opportunities in DEM to solve problems that previously were thought to be too computationally demanding. The usefulness and generality of the discrete element model strongly depends on the quality of the calibration process of the model. The process we proposed first conducts a virtual calibration of a bulk experiment that uses design of experiments, optimization and variation maps over the parameter domain to identify known optima in the virtual problem. This not only ensures a better match between the experimental and numerical model responses but also the uniqueness of the model parameters themselves. In particular, two distinct experimental and virtual calibration approaches are investigated to verify the generality of the calibrated DEM models for laboratory scale applications and future industrial applications
Bui, Tan Trung. "Etude expérimentale et numérique du comportement des voiles en maçonnerie soumis à un chargement hors plan." Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00963611.
El, Shabrawy Atef. "Comportement des ouvrages historiques soumis à des sollicitations sismiques : apport de la modélisation numérique par la méthode des éléments distincts." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL121N.