Tesis sobre el tema "Approximation de Boussinesq quadratique"
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Ferré, Alexis. "Etude CFD et expérimentale d'un stockage thermique de type thermocline". Electronic Thesis or Diss., Pau, 2024. http://www.theses.fr/2024PAUU3023.
Texto completoEnergy storage is essential to the energy transition as it allows decoupling energy production from its consumption. Water-based thermocline heat storage, used in medium or low-temperature heating networks, relies on thermal stratification in a tank. The performance of this type of storage is strongly linked to the proper stratification of the fluid, which can be disrupted by the injection and extraction of the liquid, aspects that are scarcely explored in the literature.The objective of this thesis is to reliably model such storage to analyze the fluid distribution. The aim is to better understand the physical phenomena governing the thermocline during operating cycles and to enhance its energy performance through improved design or control. To achieve this, numerical studies using CFD (Computational Fluid Dynamics) were conducted and compared with experimental data available in the literature and obtained via a new experimental setup.Initially, a CFD model was developed based on an existing experimental case from the literature. In water thermocline storage, there is often coexistence between a laminar region in the tank and a turbulent region near the distributors. This coexistence is a major challenge in modeling because most turbulence models cannot reliably represent the transition from turbulent to laminar flow. For this work, a RANS (Reynolds Average Numerical Simulation) statistical method is adopted, and the k-omega-SST model is selected as it can represent near-wall flows. Regarding buoyancy, there are two methods to consider its effects: using a variable density in all equations or a constant density except in the buoyancy term. The latter is known as the Boussinesq approximation but is only valid over a narrow range of ΔT. The accuracy of the Boussinesq approximation has been questioned, and a second-order approach of this model is employed. This allows obtaining the same buoyancy term as a variable density model but with a calculation time reduced by half. Comparison with experimental data highlighted the impact of the initial temperature state (stratified or homogeneous storage). An exploratory study of the impact of progressive injection according to a flow ramp showed its effect on reducing the thermocline thickness at the time of its creation.As part of the model validation and verification of numerical observations, a new experimental setup was designed. It measures the temperature using 300 thermocouples placed in the tank and allows precise control of operating conditions. Static phase studies to evaluate thermal losses were conducted. Dynamic studies allowed varying relevant operating parameters: axial propagation speed, temperature difference, extraction device, and progressive injection. For this system, the results show that it is possible to obtain stratification at high speed (> 2 mm/s) as long as the ΔT is sufficiently high.Finally, the flow in the test section was numerically studied with an updated CFD model. The variable fields showed that the numerical and experimental results are consistent, especially during the formation of the thermocline. However, excessive diffusion during the propagation of the thermal gradient at low flow is notable. For all the tests carried out, the experimental and numerical discrepancies were quantified: except for critical conditions, the discrepancy in thermocline thickness is ±50% and ranges from 0 to -10% for the restitution rate
McQuarrie, Shane Alexander. "Data Assimilation in the Boussinesq Approximation for Mantle Convection". BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6951.
Texto completoHaschke, Heike. "Splitting-Techniken zur spektralen Approximation der Navier-Stokes- und Boussinesq-Gleichungen". [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96361083X.
Texto completoRubio, Diana. "Distributed Parameter Control of Thermal Fluids". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30330.
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Hu, Weiwei. "Approximation and Control of the Boussinesq Equations with Application to Control of Energy Efficient Building Systems". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/38664.
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Schneider, Nicolas. "Vorticité et mélange dans les écoulements de Rayleigh-Taylor turbulents, en approximation anélastique et de Boussinesq". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066466/document.
Texto completoThe Rayleigh-Taylor instability (RTI) is especially observed in inertial confinement fusion experiments, and its development prevents the success of these experiments. The purpose of this work is to study the growth of the RTI for different compressibility regimes by using a multidomain pseudospectral Chebyshev-Fourier-Fourier simulation code. The asymptotic expansion method allows to establish several low Mach number models which do not contains acoustics. The implantation of the anelastic model, which deals with stratified fluids and captures thermal effects, has been improved. Moreover, the Boussinesq model is added to the simulation code. The accuracy of the entire numerical method is studied, as a function of the subdomain separation, and several validation elements are shown, including a comparison with an experimental study. The first simulation to be analyzed is achieved with the Boussinesq model. We focus on the self-similarity of the RTI growth. The temporal scalings of vorticity and dissipation are displayed, and the structures of turbulence and mixing are discussed. Some properties of isotropic and homogeneous turbulence are observed, however some anisotropy remains at small scales. The first three-dimensional anelastic simulations are presented. The influence of compressibility effects on the first stages of the growth is studied. Finally, a developed anelastic mixing layer involving weakly stratified fluids is described and was found to display non-negligible compressibility effects
Bérard, Bergery Blandine. "Approximation du temps local et intégration par régularisation". Thesis, Nancy 1, 2007. http://www.theses.fr/2007NAN10058/document.
Texto completoThe setting of this work is the integration by regularization of Russo and Vallois. The first part studies schemes of approximation of the local time of continuous semimartingales. If X is a reversible diffusion, the convergence of a first schema of approximation to the local time of X is proven, in probability uniformly on the compact sets. From this first schema, two other schemas of approximation for the local time are found. One converges in the semi-martingale case, the other in the Brownian case. Moreover, in the Brownian case, we estimate the rate of convergence in L^2(Omega) and a result of almost sure convergence is proven. The second part study the forward integral and the generalized quadratic variation, which have been defined by convergence of families of integrals, in probability uniformly on the compacts sets. In the case of Hölder processes, the almost sure convergence is proven. Finally, the second order convergence is studied in many cases
Toqué, Nathalie. "Diffusion turbulente anisotrope dans les zones radiatives d'étoiles". Thèse, Paris 6, 2004. http://hdl.handle.net/1866/17334.
Texto completoNguyen, Phuong Anh. "Contrôle optimal localisé sur des structures fines pour des équations paraboliques semilinéaires et le système de Boussinesq". Toulouse 3, 2000. http://www.theses.fr/2000TOU30195.
Texto completoBerard, Bergery Blandine. "Approximation du temps local et intégration par régularisation". Phd thesis, Université Henri Poincaré - Nancy I, 2007. http://tel.archives-ouvertes.fr/tel-00181777.
Texto completoMerkle, Klaus. "Einfluss gleich- und gegensinniger Drehrichtung der Verbrennungsluftströme auf die Stabilisierung turbulenter Doppeldrall-Diffusionsflammen". Karlsruhe : Univ.-Verl. Karlsruhe, 2006. http://www.uvka.de/univerlag/volltexte/2006/169/.
Texto completoFlukiger, Frédérique. "Étude statistique de la conductance d'un joint d'étanchéité statique". Toulouse, INPT, 2005. http://ethesis.inp-toulouse.fr/archive/00000193/.
Texto completoThis work is motivated by thightness technological problems associated with metallic gasket. The objective is a better understanding of leakage mecanisms, through the development of new computationals tools. In this study, the aperture field between two rough surfaces in contact is described by a short correlated isotropic random Gaussian process. The system is studied as a set of independant elementary surfaces. Joint conductances are evalueted from a statistical study on those elementary surfaces. A computational code is developed using a network approach based on lubrification theory estimation of local conductances. The global conductance computation becomes analogous to an electrical problem for wich the resistances are distributed on a random network. The network is built from the identification of the aperture field critical points. Maxima are linked through saddle points. Bond conductances are estimated at the aperture field's saddle points. First, a purely plastic model of deformations is considered. Near percolation threshold the conductances display a power behaviour. Far from percolation threshold, numerical results are favourably compared with an effective medium approximation. Secondly, we study the impact of elastic deformations. A computational code based on Boussinesq approximation is coupled to the network approach. The results indicate a significant impact of elastic deformations on conductances. Finally, the network approach is adapted to simulate quasi-static drainage thanks to a classical invasion percolation algorithm. A good comparison between previous experiments and numerical predictions is obtained
Crepeau-Jaisson, Emmanuelle. "Contrôlabilité exacte d'équations dispersives issues de la mécanique". Paris 11, 2002. http://www.theses.fr/2002PA112210.
Texto completoIn this thesis, we study the exact controlability of two dispersive equations, the Korteweg-de Vries equation and the "good" Boussinesq equation. First, for the Korteweg-de Vries equation, we extend a result of Rosier. We prove that for critical length, the nonlinear equation is exactly controlable in a neighbourhood of a small non nul stationary solution. This study uses the hilbert uniqueness method with the multiplier theory and a fixed point theorem. Secondly, we study the exact controllability of the "good" Boussinesq equation with two different boundary controls. We use again the hilbert uniqueness method but with Ingham inequality. Lastly, we apply this method for a numerical approach of the controllability of the Boussinesq equation both for linear and nonlinear equations. The control is applied to the second spatial derivative, at the right endpoint
Abouelainine, Abderrahim. "Simulation numérique de la circulation atmosphérique des planètes géantes". Paris 7, 1995. http://www.theses.fr/1995PA077001.
Texto completoThe general circulation of the giant planets is still largely unknown, because most of the phenomena remain hidden to direct observation. One of the most important problems of the meteorology of these planets is the understanding of the heat mech¬anisms maintaining the zonal circulation. The Voyager observations showed that this circulation is highly stable, and both the solar heating or the internai source could induce the general circulation, as they are of similar amplitude. This thesis brings some elements to the solution of this problem, by numerical ex¬perimentation on a jovian atmosphere's model, made of a relatively deep, rotating spherical shell (1/5' of radius) of a Boussinesq fluid, heated from two sources, one internai, isotropic, the other one external, with a pole-equator differential heating simulating the solar heating of a tropospheric layer. We obtain a "classic" convective circulation when the differential heating is weak, although it tends to stabilize the convective instability. When the differential heat¬ing becomes dominant, a new instability appears, classified "barotropic" and due to the horizontal shear of the thermal wind; Rossby waves are generated by this instability instead of the convective columns which are the prevailing motions for weak differential heating
Silva, Alex Pereira da. "Techniques tensorielles pour le traitement du signal : algorithmes pour la décomposition polyadique canonique". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT042/document.
Texto completoLow rank tensor decomposition has been playing for the last years an important rolein many applications such as blind source separation, telecommunications, sensor array processing,neuroscience, chemometrics, and data mining. The Canonical Polyadic tensor decomposition is veryattractive when compared to standard matrix-based tools, manly on system identification. In this thesis,we propose: (i) several algorithms to compute specific low rank-approximations: finite/iterativerank-1 approximations, iterative deflation approximations, and orthogonal tensor decompositions. (ii)A new strategy to solve multivariate quadratic systems, where this problem is reduced to a best rank-1 tensor approximation problem. (iii) Theoretical results to study and proof the performance or theconvergence of some algorithms. All performances are supported by numerical experiments
A aproximação tensorial de baixo posto desempenha nestes últimos anos um papel importanteem várias aplicações, tais como separação cega de fontes, telecomunicações, processamentode antenas, neurociênca, quimiometria e exploração de dados. A decomposição tensorial canônicaé bastante atrativa se comparada às técnicas matriciais clássicas, principalmente na identificação desistemas. Nesta tese, propõe-se (i) vários algoritmos para calcular alguns tipos de aproximação deposto: aproximação de posto-1 iterativa e em um número finito de operações, a aproximação pordeflação iterativa, e a decomposição tensorial ortogonal; (ii) uma nova estratégia para resolver sistemasquadráticos em várias variáveis, em que tal problema pode ser reduzido à melhor aproximaçãode posto-1 de um tensor; (iii) resultados teóricos visando estudar o desempenho ou demonstrar aconvergência de alguns algoritmos. Todas os desempenhos são ilustrados através de simulações computacionais
Thandavamoorthy, Gayathiri. "Modélisation des phénoménes transitoire lents avec la méthode de Boltzmann sur réseau". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066210/document.
Texto completoA new three-dimensional CFD solver, LaBS, based on the lattice Boltzmann alogorithms has been developed in a framework of university and industry consortium. In this thesis, this solver is used to simulate thermal flows, with a new thermal boundary condition for immersed solid boundary. The new proposed thermal boundary condition is based on the reconstruction method of the distribution function and is evaluated for immersed solid with coincident and non-coincident wall on the case of diffusion and natural convection phenomena.Renault case study, deals with a vehicle moving at constant speed (highway) that suddently slows down and stops (with or without a cut off contact). In such situation the cooling of the engine compartment first driven by forced convection during taxiing stage, abruptly switches to natural convection in low velocity stages. As natural convection is a slow process, it can take several minutes to remove the accumulated heat in the engine compartment. Such duration could be damaging for some components of the engine compartement which do not tolerate high temperature.In order to anticipate overheating of the engine compartment, where a lot of automotive parts with complex geometry are present and to avoid the above mentioned damages, the phenomenon of natural convection is here studied with the new thermal boundary condition.%The new proposed thermal boundary condition is first tested on academic case studies for validation, and then applied to the case of a real car.The modelling of thermal flows with the lattice Boltzmann method (LBM) can be classified into three categories: the multispeed approach, the hybrid approach and the double-distribution-function (DDF) approach. The multispeed approach, uses only one equation to resolve velocity, density and temperature field, which is solved by the LBM. Whereas the hybrid approach and the DDF approach utilize two sets of equations, one to resolve velocity field and density field and another to resolve temperature field. The hybrid approach solves velocity field and density field by the LBM method and the temperature field by finite-different or finite-volume methods. On the other hand the DDF approach solves the two equations with LBM.The thermal model used in the solver LaBS is based on the coupled DDF approach. In this model, the flow field is solved by a D3Q19 velocity model while the temperature field is solved by a D3Q19 or a D3Q7 velocity model. The coupling between the momentum and the energy transport is made by the boussinesq approximation. The new proposed thermal boundary condition decomposes the distribution function at the boundary node into its equilibrium and non-equilibrium part. The non-equilibrium part is calculated from the theoretical solution based on Chapman-Enskog developement.LaBS thermal model based on the coupled DDF approach is evaluated on a set of cases with increasing complexity. The results obtained with LaBS are compared with analytical solutions or with reference articles and are in a good agreement with the results expected. Results show that the model D3Q19/D3Q7 is qualitatively as good as the model D3Q19/D3Q19 but quantitatively the model D3Q19/D3Q19 remains the best
Crépeau, Emmanuelle. "Contrôlabilité exacte d'équations dispersives issues de la mécanique". Phd thesis, Université Paris Sud - Paris XI, 2002. http://tel.archives-ouvertes.fr/tel-00003637.
Texto completoEl, Fassi Kaouthar. "Sur l'estimation non paramétrique de la fonction d'égalisation équipercentile. Application à la qualité de vie". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00425330.
Texto completoChayé, Isabelle. "Modélisation par éléments finis de frontière de la diffraction électromagnétique des surfaces". Compiègne, 1991. http://www.theses.fr/1991COMPD424.
Texto completoThai, Quynh Phong. "Analyse numérique des méthodes d'optimisation globale. Codes et simulations numériques. Applications". Rouen, 1994. http://www.theses.fr/1994ROUES069.
Texto completoChazel, Florent. "Influence de la topographie sur les ondes de surface". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2007. http://tel.archives-ouvertes.fr/tel-00200419.
Texto completoHaddad, Adel. "Modèles numériques à faibles nombres de Mach pour l'étude d'écoulements en convection naturelle et mixte". Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10154.
Texto completoThe 3D numerical model which we developed in this thesis presents two main features: a Low-Mach-Number approximation for water along with an open boundary condition formulation. Indeed, the difficulties related to the former point stand in a computationally efficient adaptation of the water equation of state in the framework of Low Mach number approximation, whereas the difficulties related to the latter concern the introduction of Open Boundary Conditions in the projection algorithm used. We have computed a mixed convection flow in a horizontal channel uniformly heated from below and compared the results obtained with both the Boussinesq approximation and experimental results
Haschke, Heike [Verfasser]. "Splitting-Techniken zur spektralen Approximation der Navier-Stokes- und Boussinesq-Gleichungen / von Heike Haschke". 2001. http://d-nb.info/96361083X/34.
Texto completoPanse, Shreyas S. "Background and Available Potential Energy in Numerical Simulations of a Boussinesq Fluid". 2013. https://scholarworks.umass.edu/theses/1002.
Texto completoDostalík, Mark. "Vliv materiálových parametrů na stabilitu termální konvekce". Master's thesis, 2016. http://www.nusl.cz/ntk/nusl-346943.
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