<p>QC 20140428</p>

While there has been a great deal of research on air entrainment at hydraulic jumps within closed conduits, very little of the research has specifically addressed size and temperature scale effects. Influences from jump location and changing length characteristics on air entrainment have also received little attention from past research. To determine the significance of size-scale effects of air entrained by hydraulic jumps in closed conduits, air flow measurements were taken in four different-sized circular pipe models with similar Froude numbers. Each of the pipe models sloped downward and created identical flow conditions that differed only in size. Additionally, specific measurements were taken in one of the pipe models with various water temperatures to identify any effects from changing fluid properties. To determine the significance of the effects of changed length characteristics on air demand, air flow measurements were taken with hydraulic jumps at multiple locations within a circular pipe with two different air release configurations at the end of the pipe. Results showed that air demand was not affected by the size of the model. All together, the data from four different pipe models show that size-scale effects of air entrained into hydraulic jumps within closed conduits are negligible. However, it was determined that air entrainment was significantly affected by the water temperature. Water at higher temperatures entrained much less air than water at lower temperatures. Hydraulic jump location results showed that for both configurations the percentage of air entrainment significantly increased as the hydraulic jump occurred near the point of air release downstream. As the jump occurred nearer to the end of the pipe, its length characteristics were shortened and air demand increased. However, jump location was only a significant factor until the jump occurred some distance upstream where the length characteristics were not affected. Upstream of this location the air demand was dependent only on the Froude number immediately upstream of the jump.

La variabilité spatio-temporelle du ruissellement et de l'érosion hydrique n'est pas un fait nouveau. Leurs caractéristiques s'estiment généralement avec une marge raisonnable sur des parcelles d'un à quelques dizaines de m². Avec l'accroissement de la surface, l'hétérogénéité du milieu croît ce qui induit un effet d'échelle. Le passage de la parcelle au bassin versant n'est pas totalement maîtrisé compte tenu de la complexité et de la variabilité des facteurs mis en jeu. L'objectif de cette thèse est de comprendre les processus de ruissellement et de l'érosion dans différents environnements et à différentes échelles spatiales, d'identifier les sources de variation, puis de développer une méthodologie de transposition des résultats de l'échelle parcellaire à l'exutoire du bassin versant. À cet effet, un réseau de dix-huit parcelles expérimentales de différentes tailles, de deux unités hydrologiques ont permis de quantifier le ruissellement et les pertes en terre sur les principaux états de surface du bassin versant de Tougou.Les résultats obtenus sur les micro-parcelles de 1m², les parcelles de 50 et 150m², les unités hydrologiques de 6 et 34 ha et le bassin versant de 37km², montrent que, tant sur sols cultivés que sur sols dénudés, la lame ruisselée ainsi que les pertes en terres diminuent lorsque la superficie augmente, pour une même pluie et dans des conditions comparables d'humidité préalable des sols. Ce phénomène d'effet d'échelle de la superficie sur l'écoulement et l'érosion est connu des hydrologues qui se heurtent toujours à l'écueil de l'extrapolation des résultats obtenus sur petites superficies à des superficies plus grandes. Nos résultats montrent que l'effet d'échelle observé sur le ruissellement et l'érosion est dû principalement à l'hétérogénéité spatiale des sols (propriétés hydrodynamiques, microrelief) et à sa variabilité (état des variables) et que la dynamique temporelle de l'intensité de la pluie ne fait que l'amplifier.Les résultats obtenus lors des essais de transposition permettent de soutenir avec raison qu'une meilleure extrapolation des données de l'échelle parcellaire à l'échelle du bassin viendra de la prise en compte des questions de la connectivité hydrologique.En définitive, cette étude met en avant l'intérêt d'effectuer des mesures de ruissellement et d'érosion sur des unités homogènes en termes d'occupation du sol qui peuvent représenter une mosaïque hétérogène de surfaces homogènes. La localisation sur le bassin versant et le taux de connectivité de ces unités hydrologiques à l'intérieur desquelles les processus dominants du ruissellement et d'érosion se manifestent peuvent permettre d'approcher la résolution du problème de transfert d'échelle. / The spatio-temporal variability of runoff and erosion is not new fact. Their characteristics are generally estimated with a reasonable margin on plots of a few tens of square meters. With the increase of the surface, the heterogeneity of environment increases which induces a scale effect. The passage of the plot to the catchment is not totally controlled because of the complexity and variability of factors come into play. The objective of this thesis is to understand the processes of runoff and erosion in different environments and at different spatial scales, to identify the sources of variation, and to develop a methodology for implementation of the results of field scale to the basin outlet. To this end, a network of eighteen plots of different sizes, two hydrological units were used to quantify runoff and soil loss on the main surface features Watershed Tougou.The results obtained on micro-plots of 1 m², plots of 50 and 150 m², hydrologic units of 6 and 34 ha and the catchment area of 37 km², show that, both in cultivated soils and on bare soils, the runoff excess decreases as the area increases, for the same rain and prior comparable humidity conditions of the soil. This phenomenon of the scale effect of the area on runoff is known to hydrologists who still face the challenge of extrapolating results obtained on small areas to larger areas. Our results show that the scale effect observed on the runoff is mainly due to the spatial heterogeneity of soils (hydraulic properties, microrelief) and its variability (state of the variables) and that temporal dynamics of the intensity of rain just amplifies it. The results obtained in tests of transposition can maintain with reason that a better extrapolation of data from the field scale across the pond comes from the consideration of the issues of hydrologic connectivity.Ultimately, this study highlights the value of measurements of runoff on homogeneous units in terms of land use that may represent a heterogeneous mosaic of homogeneous areas. The location on the watershed and the rate of connectivity of the hydrologic units within which the dominant processes of runoff occur can allow approach the solution of the problem of scale transfer.

Ce travail de thèse s’inscrit dans le cadre de la modélisation distribuée de la partition ruissellement-infiltration en milieu naturel. Notre démarche consiste à étudier la réponse de systèmes naturels complexes à partir de mesures locales, d’expérimentations numériques et de modèles distribuées. Les expériences de la parcelle de Thiès (40m2), au Sénégal, montrent que les hétérogénéités de rugosités mettent en défaut les lois de friction classiques (Manning, Darcy- Weisbach) des modèles de ruissellement qui sous estiment les hautes vitesses. Deux lois qui prennent en compte la hauteur de submersion de la rugosité de manière physique ou empirique sont testées. Dans le bassin versant de Houay Pano, les données obtenues sous pluie simulées, sur des placettes de 1m2, permettent de mettre en évidence l’effet des hétérogénéités, en particulier en terme d’encroutement du sol et de végétation, sur le ruissellement intégré spatialement. L’infiltration moyenne apparait comme dépendante de l’intensité de pluie et l’effet d’une distribution statistique d’infiltrabilité sur le transitoire et le permanent d’infiltration est étudié. La distribution exponentielle d’infiltrabilité semble la plus adaptée, elle est utilisée pour analyser la variabilité spatiale et temporelle de la production de ruissellement dans le bassin versant sous pluie naturelle. Enfin, ce modèle exponentiel, simple mais pertinent à l’échelle du mètre, est implémenté pour représenter un pixel de base dans un modèle de ruissellement-infiltration à l’échelle d’un sous bassin versant de 0.5 ha et différents scénarios de modélisation sont envisagés / This work deals with distributed modeling of runoff-infiltration processes in a natural environment. The response of complex natural systems is studied from local measurements, numerical investigations and distributed models. Experiments held in Thies, Senegal, on a 40m2 plot show that the heterogeneity of the surface put in the wrong classical friction laws (Manning, Darcy-Weisbach) of runoff models, because they underestimate high velocities. Two laws, taking physically or empirically into account the submersion of rugosity, are tested. In the Houay Pano catchment, we highlight from simulated rainfall experiments on 1m2 plots the effects of heterogeneities, mainly due to soil crusting and vegetation, on the spatially integrated runoff. We observed that the mean infiltration rate is dependent of the rainfall intensity and studied the effects of a statistical distribution of infiltrabilities on permanent and non-permanent infiltration. The exponential distribution of infiltrabilities appeared to be the best suited distribution. It is used to analyze spatial and temporal variability of runoff production in the catchment under natural rainfall, in order to obtain a per land use characterization of infiltration. Eventually, this simple but accurate model at the meter scale is implemented as a base pixel into a runoff-infiltration model at the sub-catchment scale (0.5 ha)

Dans cette thèse, des considérations fondamentales de modélisation des phénomènes de rupture sont abordées pour des systèmes discrets endommageables. Le but est d’établir, en commençant par des problèmes structuraux simples, un pont entre la Mécanique de l’Endommagement Discret (MED) et celle de la Mécanique de l’Endommagement Continu (MEC) non local. Il est actuellement admis que la MEC doit être considérée dans un cadre non local afin d’obtenir des résultats cohérents, notamment lors de la modélisation numérique de phénomènes de radoucissement basés sur des lois d’endommagement. Nous appuyons cette non-localité sur l’échelle de la microstructure du matériau. A l’aide d’une procédure de continualisation et l’utilisation de l’approximant de Padé, nous avons pu obtenir l’expression analytique de l’approximation continue non-locale offrant une représentation très fidèle du comportement du problème discret dans tout le processus d’endommagement. Nous étudions les systèmes de la chaîne axiale discrète en traction, de la poutre console discrète en flexion ainsi que de la membrane microstructurée sous pression uniforme. Le système discret est tout d’abord résolu puis les équations discrètes sont continualisées pour obtenir un modèle non local continu. Pour chacun de ces problèmes une attention toute particulière est portée aux conditions aux limites du problème continualisé, dont l’importance est illustrée tout au long de ce manuscrit. / In this thesis, some fundamental considerations of the modeling of failure are addressed for discrete damage systems. The goal is to establish, starting with simple structural problems, a bridge between the Discrete Damage Mechanics (DDM) and that of the non-local Continuum Damage Mechanics (CDM). It is currently accepted that DDM systems must be considered in a non-local framework to obtain consistent results, especially during numerical modeling of softening phenomena based on damage laws. We support this non- locality on the scale of the microstructure of the material. Using a continualisation procedure and with the use of the Padé approximant, we were able to obtain the analytic expression of the non-local continuous approximation offering an accurate simulation of the discrete problem for the whole damage process. We study the systems of the discrete axial chain under traction, the discrete bending beam and the microstructured membrane under uniform pressure. The discrete system is first solved, then the discrete equations are continualised to obtain a non-local continuum model. For each of these problems, careful attention is paid to the boundary conditions of the continual problem, the importance of which is illustrated throughout this manuscript.

No description available.

L’origine des incendies domestiques peut être aussi diverse qu’une mauvaise installation électrique, une cigarette mal éteinte, un mauvais entretien d’une cheminée… Ce mémoire traite de l’inflammabilité de différents matériaux de l’habitat face à une source radiative. Plusieurs paramètres tels que la dimension, l’orientation et la nature des matériaux ont été étudiés dans des conditions opératoires similaires. Ces travaux ont conduit au développement d’un nouveau dispositif expérimental permettant de travailler à différentes échelles : le RAPACES (RAdiant PAnel Concentrator Experimental Setup). Les résultats obtenus sur le PMMA ont permis de mettre en évidence que les facteurs géométriques jouent un rôle prépondérant; d’une part sur l’ignition (variation des propriétés thermo-radiatives) et d’autre part sur la dynamique de combustion à travers des phénomènes structuraux (déstabilisation structurelle, affaissement et écoulement du matériau). Cette démarche a également été appliquée à des matériaux plus complexes (contreplaqué, tapisserie, moquette). L’utilisation d’un modèle numérique a permis de valider certaines hypothèses concernant le comportement au feu du PMMA. Enfin, des configurations originales constituées d’assemblages de matériaux ont été testées et ont permis de mettre en évidence les interactions entre combustibles en termes d’ignition et de propagation de flamme. / The origin of home fires can be as diverse as poor wiring, a smoldering cigarette, poor maintenance of a fireplace... This manuscript deals with the flammability of various household materials exposed to a radiative source. Several parameters such as dimension, orientation and nature of materials were investigated in similar operating conditions. These studies led to the development of new experimental device enabling working at different scales: RAPACES (RAdiant PAnel Concentrator Experimental Setup). The results obtained on PMMA showed that geometric factors play a major role (i) on ignition (variation of thermal radiative properties) and (ii) on combustion dynamics through structural phenomena (destabilization, collapsing and polymer melting). This approach was also applied to complex materials (plywood, tapestry, carpet). A numerical model was used to validate some hypothesis regarding the fire behavior of PMMA. Finally, original configurations including material assemblies were performed and clearly evidenced the effect of fuel interactions on ignition and flame propagation.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A erosÃo, o transporte e a deposiÃÃo de sedimentos sÃo questÃes ambientais que afetam a sociedade, principalmente devido ao decrÃscimo da produtividade agrÃcola, à diminuiÃÃo da capacidade de armazenamento dos reservatÃrios, à intensificaÃÃo dos processos de desertificaÃÃo, à ocorrÃncia de inundaÃÃes e à reduÃÃo da disponibilidade hÃdrica. A tendÃncia atual dos estudos hidrosedimentolÃgicos à abordar grandes escalas, a fim de gerar resultados com implicaÃÃes para o planejamento das bacias hidrogrÃficas. PorÃm, o monitoramento e a anÃlise hidrosedimentolÃgica de sub-bacias sÃo de grande importÃncia para o entendimento dos processos locais. AlÃm disso, esses estudos, quando consistentes, se tornam parte do banco de dados das investigaÃÃes que englobam os grandes sistemas, em algumas situaÃÃes, a escala global. Objetiva-se com esta pesquisa estudar a produÃÃo especÃfica de sedimentos na Bacia do Rio Jaguaribe (BRJ), com a proposta de analisar as relaÃÃes entre esta variÃvel e a Ãrea de drenagem, a fim de identificar se os dados possuem alometria com a escala espacial. Os dados de produÃÃo de sedimentos foram obtidos de fontes primÃrias e secundÃrias, contemplando diferentes mÃtodos de mediÃÃo e larga faixa de Ãreas (6,8 x 10-5 km a 4,8 x 104 kmÂ). Os dados primÃrios advieram do monitoramento de uma seÃÃo hidrosedimentolÃgica automatizada, monitoramento de uma encosta por pinos de erosÃo e batimetrias de reservatÃrios. Os dados secundÃrios foram originados de investigaÃÃes anteriores conduzidas em diversas escalas de sub-bacias do Rio Jaguaribe, tambÃm contemplando diferentes mÃtodos de mediÃÃo. Os resultados encontrados por esta pesquisa mostram que: (i) a calibraÃÃo do turbidÃmetro por meio da resuspensÃo de sedimentos se mostrou uma alternativa plausÃvel para as condiÃÃes semiÃridas. A melhoria da escala temporal no monitoramento sedimentolÃgico atravÃs das medidas de turbidez permitiu uma anÃlise mais representativa da dinÃmica da concentraÃÃo de sedimentos suspensos da seÃÃo estudada; (ii) a produÃÃo de sedimentos mÃdia da BRJ foi de 347 t km-2 ano-1, mÃnimo de 1,1 t km-2 ano-1 e mÃximo de 1.340 t km-2 ano-1; (iii) os atributos erosividade, geologia e cobertura vegetal, quando analisados separadamente, nÃo induziram a nenhuma relaÃÃo clara entre a produÃÃo especÃfica de sedimentos e a Ãrea de drenagem. PorÃm, as bacias com cobertura vegetal acima de 80% tiveram uma mÃdia de produÃÃo de sedimentos de 139 t km-2 ano-1, enquanto aquelas com cobertura inferior a 40% obtiveram mÃdia de 545 t km-2 ano-1, evidenciando a importÃncia da vegetaÃÃo na reduÃÃo da desagregaÃÃo do solo e transporte de sedimentos; (iv) o presente estudo indicou que a relaÃÃo entre produÃÃo de sedimentos e Ãrea de drenagem do Rio Jaguaribe, com alometria positiva para Ãreas de atà 400 kmÂ, nÃo seguiu o padrÃo regular estabelecido pelos dados de muitos rios do mundo. Salvo melhor juÃzo, a alometria positiva encontrada por este trabalho à inÃdita para regiÃes nÃo glaciais; (v) a alometria positiva encontrada por esta pesquisa pode ser um indicativo de que a DepressÃo Sertaneja, unidade geomorfolÃgica principal da BRJ, ainda està em fase de ajustamento, ou seja, os processos de erosÃo responsÃveis pelo aplainamento da superfÃcie estariam contribuindo para o aumento da produÃÃo de sedimento atà uma determinada faixa de escala. A partir da Ãrea (400 kmÂ) na qual se inicia o decaimento da produÃÃo de sedimento, os processos de deposiÃÃo dos sedimentos passam a ser dominantes sobre os processos de produÃÃo e transporte. / Erosion, transport and sediment deposition are environmental issues that affect society, mainly due to the decrease in agricultural production, decreased storage capacity of reservoirs, the intensification of desertification processes, the occurrence of floods and reduction of water availability. The current trend of the hydrosedimentological studies is addressing large scale in order to generate results with implications to planning of basins. Therefore, the monitoring and hydrosedimentological analysis of the sub-basins are of great importance for the understanding of local processes, in addition, these studies when consistently, become part of the database of investigations that cover large systems, in some situations, the global scale. The objective of this research is to study the specific sediment yield in the Jaguaribe River Basin (JRB), with the proposal to examine the relationship between this variable and the drainage area in order to identify if the data have an allometry trend with the spatial scale. The specific sediment yield data were obtained from primary and secondary sources, covering different measurement methods and a wide range of areas (6.8 x 10-5 km to 4.8 x 104 kmÂ). The primary data were originated from an automated hydrosedimentological section, monitoring of hillslope by erosion pins and reservoirs bathymetric surveys. Secondary data were originated from previous investigations conducted in several sub-basins of the Jaguaribe River, also contemplating different measurement methods and scales. The results of this research show that: (i) the calibration of the turbidimeter by sediment re-suspension method was shown to be as a reasonable alternative to semiarid conditions. Improvement at timescale of the sedimentological measures by turbidity allowed a more representative analysis of the suspended sediment concentration dynamics at studied control section; (ii) average specific sediment yield of the JRB was 347 t km-2 yr-1, the least was 1.1 t km-2 year-1 and the maximum was 1,340 t km-2 year-1; (iii) the attributes erosivity, geology and vegetation cover, when analyzed separately, didnât induce any clear relationship between specific sediment yield and drainage area. However, the watersheds with vegetation cover over 80% had an average sediment yield of 139 t km-2 year-1, while those with vegetation cover less than 40% achieved an average of 545 t km-2 year-1, showing the importance of vegetation in reducing soil detachment and sediment transport; (iv) the present study indicated that the relationship between sediment yield and drainage area of the Jaguaribe River, with positive allometry to areas up to 400 kmÂ, did not follow the regular pattern established by the data of many rivers in the world. Saved better judgment, the positive allometry found in this study is novel to with not-glacial behavior regions; (v) the positive allometry found in this research may be interpreted that the DepressÃo Sertaneja, the main geomorphological unit in the JRB, is still in adjustment phase, where the erosion processes responsible for the leveling of the surface are contributing to increase sediment yield up to certain scale. Above the area (400 kmÂ) at which specific sediment yield begins decreased, the process of sediment deposition becomes dominant upon production and transport processes.

This thesis analyzes the potential systematic errorin the characterization of the rock mass quality in borehole and tunnel mapping. The difference when assessing the rock mass quality refers to the fact that the characterization performed on drilled rock cores are commonly done on-meter length, while the tunnel section can be up to 20-25 m wide. At the same time, previous studies indicate that the engineering geologist tends to characterize the rock mass quality during tunnel excavation with a conservative estimation of the parameters defining the rock mass quality to ensure a sufficient rock support. In order to estimate this possible systematic error produced by the size difference when assessing the rock mass quality, a simulation was performed within a geological domain, representative of Stockholm city. In the simulation, each meter of the tunnel section was given a separate value of the rock mass quality, randomly chosen from a normal distribution representative for the studied geological domain. The minimum value was set to represent the characterized rock mass quality for that tunnel section. The results from the simulation produced a systematic error due to the difference between the geological domain, reproducing the borehole mapping, and the simulated values, representing the tunnel mapping. The results showed a systematic error in the RMR basic index around 15 points in average, which compared to the difference of 5-7 points obtained in Norrström and the Norrmalm tunnels in the Stockholm Citylink project recently constructed, are found to be excessive. However, in the simulation, it was assumed that (1) the results obtained were the same in the bore hole mapping and in the tunnel mapping, (2) with the only difference of the engineer geologist assigning to the tunnel section the lowest RMR basic value, and (3) that there was no spatial correlation between the quality RMR basic index. After analyzing the three assumptions the simulation was based upon, the absence of spatial correlation was found to be the most significative, which indicate that spatial correlation in rock mass quality needs to be included if a more correct value should be obtained.

No description available.