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331	Modélisation multidimensionnelle des pressions et teneurs en eau dans le sol et le sous-sol : effets capillaires et gravitaires en présence d'hétérogénéités et de fluctuations / Multidimensional modeling of pressures and water contents in soils and the subsurface : capillary and gravitational effects in the presence of heterogeneity and fluctuations Mansouri, Nahla 11 July 2016 (has links) Cette recherche doctorale porte sur la modélisation 3D de la dynamique des teneurs en eau dans le sol et le soussol lorsque les écoulements sont à saturation variable. La modélisation est basée sur une version généralisée de la loi de Darcy-Buckingham et de l’équation de Richards multidimensionnelle. Les recherches présentées dans cette thèse concernent différents volets, présentés ci-dessous, dont le fil conducteur est l’analyse de phénomènes d’écoulements en milieux poreux, contenant de fortes hétérogénéités et/ou perturbés par des fluctuations temporelles. Dans le cadre d’un partenariat de recherche entre l’IMFT et l'IRSN sur la problématique du stockage souterrain de déchets radioactifs, nous avons modélisé en 3D la dynamique du front de désaturation d’une couche argileuse autour d’une galerie souterraine ventilée, à l’aide du code volumes finis BIGFLOW 3D. Ce travail a permis de mettre au point une approche d’immersion pour la modélisation des écoulements en milieux composites. Un autre volet de cette thèse concerne une étude analytique et numérique des profils verticaux de succion et de teneur en eau lors d’une infiltration verticale, non-saturante, dans un sol hétérogène finement stratifié. Des solutions analytiques exactes et approchées sont obtenues en régime permanent, à l’aide de transformations de variables, et sont comparées avec des solutions numériques pour différents degrés d’hétérogénéité. De même, les phénomènes de « barrière capillaire » sont étudiés d’une part analytiquement et d’autre part, par expérimentations numériques transitoires d’infiltration sur des systèmes bicouches, en présence d’une nappe plus ou moins profonde. D’autre part, les écoulements nonsaturés sont étudiés, cette fois, en présence d’un forçage transitoire fortement oscillatoire, dans une colonne de sable fin homogène, sous l’effet de fluctuations périodiques du niveau de la surface libre. Une méthode multi-front mise au point lors d’une thèse précédente à l’IMFT est validée numériquement en montrant que cette méthode simule efficacement la dynamique oscillatoire des flux et des profils de pression avec un nombre limité de « fronts ». De plus, nous avons analysé la phénoménologie capillaire/gravitaire des écoulements oscillatoires dans la colonne grâce à un suivi dynamique du plan de flux nul. Enfin, nous présentons, comme extension aux travaux précédents, une étude préliminaire des phénomènes 3D d’infiltration et de redistribution d’eau, notamment lorsque l’hétérogénéité du sol est de type aléatoire. Les premiers essais d’infiltration permettent de tester, en réplique unique, des méthodes de prises de moyennes spatiales des champs de succion et teneur en eau et évaluer la taille minimum du domaine de calcul 3D permettant d’obtenir des profils verticaux moyens représentatifs de l’infiltration dans une réplique unique du sol aléatoire. / This doctoral research, defended at the Institut de Mécanique des Fluides de Toulouse, is devoted to modeling water pressure and water content in soils and in subsurface geologic formations, in the case of variably saturated flow. One of the main scientific objectives of this work is to analyze the response of unsaturated flow systems, and particularly capillary and gravitational effects, in the presence of material heterogeneities, discontinuities, and/or space-time fluctuations. Modeling is based on a generalized version of Darcy- Buckingham’s law, and of Richards’ flow equation. Overall, the topics developed in this PhD thesis focus on several related aspects of variably saturated water flow in the subsurface. These aspects all occur at once in most applications (drying/wetting,heterogeneity, temporal forcing), but they are "decoupled" here for convenience. A preliminary research (collaborative project IMFT / IRSN) was developed to study the 2D/3D drying process at the porous wall of a deep cylindrical excavation in response to hydrometeorological signals. This project has motivated the design and testing of a novel approach to include cavities in the modeling domain. A detailed study of steady state infiltration was developed for the case of finely stratified soils, with parameters that vary continuously and cyclically with depth. Exact and approximate analytical solutions are calculated based on variable transformation methods and on perturbation type approximations, and they are tested numerically using a finite volume code (BIGFLOW 3D). The sensitivity of suction fluctuations vs. stratification wavelength is investigated, as well as the effect of the degree of heterogeneity, and of water table depth. Capillary barrier effects are studied for the case of unsaturated infiltration in multilayer soil systems characterized by a discontinuity of soil properties at interfaces. Numerical experiments are developed for transient infiltration towards a water table through a two-layer system, the goal being to analyze possible capillary barrier effects under various scenarios. On the other hand, we study numerically the case of a partially saturated / unsaturated soil column submitted to highly variable oscillatory pressure at the bottom of the column: this leads to vertical flow oscillations in the unsaturated zone above the water table influenced by tides (coastal beach sand). We analyze the dynamics of this oscillatory flow, where capillary and gravitational effects compete; for this purpose we use a novel method that tracks the positions of the zero flux plane in the unsaturated column. Finally, we also present, as an extension to the previous studies, a preliminary investigation of multidimensional infiltration/redistribution phenomena, particularly for the case of fully 3D random-type soil heterogeneity. The first numerical experiments of 3D infiltration are undertaken based on the single realization approach to soil heterogeneity, and assuming a uniform distribution of wetting at soil surface. Hydrologie des sols Ecoulements non saturés Sols stratifiés et multicouches Cavités souterraines Modélisation numérique Teneurs en eau Succion Effets capillaires et gravitaires Darcy Richards Soil hydrology Hydrogeology Infiltration Stratified and multilayer soils Subsurface cavities Karsts Subsurface waste disposal Numerical modeling Suction Capillary and gravitational effects Darcy Richards Water content
332	Studies on instability and optimal forcing of incompressible flows Brynjell-Rahkola, Mattias January 2017 (has links) This thesis considers the hydrodynamic instability and optimal forcing of a number of incompressible flow cases. In the first part, the instabilities of three problems that are of great interest in energy and aerospace applications are studied, namely a Blasius boundary layer subject to localized wall-suction, a Falkner–Skan–Cooke boundary layer with a localized surface roughness, and a pair of helical vortices. The two boundary layer flows are studied through spectral element simulations and eigenvalue computations, which enable their long-term behavior as well as the mechanisms causing transition to be determined. The emergence of transition in these cases is found to originate from a linear flow instability, but whereas the onset of this instability in the Blasius flow can be associated with a localized region in the vicinity of the suction orifice, the instability in the Falkner–Skan–Cooke flow involves the entire flow field. Due to this difference, the results of the eigenvalue analysis in the former case are found to be robust with respect to numerical parameters and domain size, whereas the results in the latter case exhibit an extreme sensitivity that prevents domain independent critical parameters from being determined. The instability of the two helices is primarily addressed through experiments and analytic theory. It is shown that the well known pairing instability of neighboring vortex filaments is responsible for transition, and careful measurements enable growth rates of the instabilities to be obtained that are in close agreement with theoretical predictions. Using the experimental baseflow data, a successful attempt is subsequently also made to reproduce this experiment numerically. In the second part of the thesis, a novel method for computing the optimal forcing of a dynamical system is developed. The method is based on an application of the inverse power method preconditioned by the Laplace preconditioner to the direct and adjoint resolvent operators. The method is analyzed for the Ginzburg–Landau equation and afterwards the Navier–Stokes equations, where it is implemented in the spectral element method and validated on the two-dimensional lid-driven cavity flow and the flow around a cylinder. / <p>QC 20171124</p> hydrodynamic stability optimal forcing resolvent operator Laplace preconditioner spectral element method eigenvalue problems inverse power method direct numerical simulations Falkner–Skan–Cooke boundary layer localized roughness crossflow vortices Blasius boundary layer localized suction helical vortices lid-driven cavity cylinder flow Fluid Mechanics and Acoustics Strömningsmekanik och akustik
333	Análisis de la envolvente de falla de un suelo fino mediante la succión matricial utilizando el método de talud infinito aplicado a una cobertura de talud Linares Ramos, Alexander Yamil, Mejía Melo, Paola 30 October 2020 (has links) La construcción de coberturas en zonas alto andinas se ha convertido en una pieza clave para disminuir los pasivos ambientales y, a la vez, contribuir el desarrollo del país gracias a la minería. Gran parte del terreno en estas zonas son suelos arcillosos cuyo comportamiento es impredecible porque presentan cambios de volumen abruptos según la variación de saturación del suelo. Quienes transitan por carreteras en taludes de este tipo de suelo, corren alto riesgo debido al deslizamiento que sufren los taludes cada año. En este tipo de taludes se producen deslizamientos cuando el suelo arcilloso se encuentra parcialmente saturado, ya que en estas condiciones el suelo no es estable. Por ello, se realizaron los estudios de estabilidad de taludes de suelo parcialmente saturado con el método de talud infinito. Se construyó la envolvente de falla del suelo parcialmente saturado con los valores del ensayo del papel filtro y corte directo de acuerdo con la saturación a la que se encuentre sometido. Estos valores serán importantes para el cálculo del factor de seguridad, el cual se obtuvo a partir de una hoja de cálculo propuesta en esta investigación. Finalmente, se validó la hoja de cálculo con el software Geostudio donde se obtuvo una variación dentro del rango de significancia +-5%. Se concluyó que el análisis de estabilidad de talud de cobertura de un suelo parcialmente saturado proporciona un valor de factor de seguridad a partir de un análisis que simula con mayor exactitud el comportamiento del suelo. / The construction of hedges in high Andean areas has become a key element in reducing environmental liabilities and, at the same time, contributing to the development of the country thanks to mining. Much of the terrain in these areas is clay soils whose behavior is unpredictable because they present abrupt volume changes depending on the variation in soil saturation. Those who travel on roads on slopes of this type of soil are at high risk due to the landslide suffered by the slopes every year. In this type of slopes, landslides occur when the clay soil is partially saturated, since under these conditions the soil is not stable. For this reason, the stability studies of partially saturated soil slopes were carried out with the infinite slope method. The partially saturated soil failure envelope was constructed with the values of the filter paper test and direct cut according to the saturation to which it is subjected. These values will be important for the calculation of the safety factor, which was obtained from a spreadsheet proposed in this investigation. Finally, the spreadsheet was validated with the Geostudio software, where a variation was obtained within the range of significance + -5%. It was concluded that the slope stability analysis of a partially saturated soil cover provides a factor of safety value from an analysis that more accurately simulates soil behavior. / Tesis Suelos parcialmente saturados Estabilidad de taludes Succión matricial Saturación parcial Método de papel filtro Curva característica Cobertura Partially saturated soils Slope stability Matrix suction Partial saturation Filter paper method Characteristic curve
334	Untersuchung der Geschosswirkung in der sehr frühen Phase unter besonderer Berücksichtigung der Hochgeschwindigkeitsmunition / Study of bullet effects at a very early stage with special consideration of high-speed ammunition Siegmund, Bernward 13 November 2006 (has links) No description available. 610 Medizin, Gesundheit Medicine Ausschuss ballistische Gelatine ballistisches Pendel Druckwelle Druckverlauf Energieabsorption Energieverlust Einschuss Energieabgabe Fragmentation Frangible Training Ammution Gewehr Geschwindigkeit Geschosse gerichtliche Medizin Glasfaserhydrophon Geometrie Hochgeschwindigkeit Hochgeschwindigkeitskamera Hochgeschwindigkeitsmunition Jagdunfälle Kaliber Kavitation Kaliber Militär Munition Projektil Reflexion Rechtsmedizin Schallgeschwindigkeit Schussverletzungen Schusswaffen Schusswirkung Schusswunden temporäre Zielhöhle Tötungsdelikt Vollmantelmunition Wechselwirkung Wundballistik Zugwelle Zielballistik Zielpulsation ammunition ballistic gelatine ballistic pendulum bullet bullet hole calibre cavitation energy absorption energy emission firearm forensic medicine fragmentation frangible training ammunition full metal ammunition geometry glass fibre hydrophone gunshot wound high speed high speed camera homicide hunting accident interaction loss of energy medial jurisdiction military pressure progression projectiles rejects reflection rifle shot effect shock wave speed speed of sound suction waves target ballistics target pulsation temporary target cave wound ballistics 44.72 MED 590: Rechtsmedizin

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