Le transport de la neige par le vent est une composante importante de l'interaction entre l'atmosphère et la cryosphère. En zone de montagne, il influence la distribution temporelle et spatiale de la couverture neigeuse au cours de l'hiver et a en premier lieu des conséquences sur le danger d'avalanche. La modélisation numérique de ce phénomène permet d'étudier les interactions complexes entre le manteau neigeux et le vent et d'en estimer les conséquences de manière distribuée. Dans ce contexte, cette thèse décrit le développement et l'évaluation d'un modèle couplé atmosphère/manteau neigeux dédié à l'étude du transport de la neige par le vent en zone de montagne reposant sur le modèle atmosphérique Meso-NH et le modèle détaillé de manteau neigeux Crocus. Le transport de la neige par le vent a été étudié sur le site expérimental du Col du Lac Blanc (massif des Grandes Rousses, France). Une base de données d'épisodes de transport couvrant dix hivers a tout d'abord été utilisée pour déterminer les caractéristiques principales de ces épisodes. Des simulations avec le modèle Crocus (non couplé à Meso-NH) ont ensuite montré qu'il était nécessaire de tenir compte des transformations mécaniques des grains de neige induites par le vent afin de simuler une évolution réaliste de la vitesse seuil de transport. Le site expérimental a également été le siège de deux campagnes de mesures en 2011 et 2012 visant à collecter de données de validation pour le modèle. Elles renseignent sur les conditions météorologiques près de la surface, sur les quantités de neige transportées et sur la localisation des zones d'érosion et de dépôt de la neige grâce à l'utilisation d'un laser terrestre. Le modèle de transport de neige par le vent Meso-NH/Crocus a été développé. Il intègre le transport de la neige en saltation et en suspension turbulente ainsi que la sublimation des particules de neige transportée. Un schéma à deux moments permet de simuler l'évolution spatiale et temporelle de la distribution en taille des particules. L'utilisation d'un schéma de couche limite de surface à l'interface entre Meso-NH et Crocus s'est révélé nécessaire pour représenter les forts gradients de concentration en particules de neige observés près de la surface. Meso-NH/Crocus est le premier modèle couplé atmosphère/manteau neigeux capable de simuler de manière interactive le transport de la neige par le vent en zone alpine. Meso-NH/Crocus a été évalué en relief réel grâce aux données collectées lors de la première campagne de mesure en 2011. La simulation d'un épisode de transport sans chute de neige simultanée montre que le modèle reproduit de manière satisfaisante les principales structures d'un écoulement en relief complexe ainsi que les profils verticaux de vitesse de vent et de flux de particules de neige en suspension près de la surface. En revanche, la résolution horizontale de 50 m est insuffisante pour reproduire avec précision la localisation des zones d'érosion et de dépôt autour du Col du Lac Blanc. La prise en compte de la sublimation réduit la quantité de neige déposée de l'ordre de 5%.Les techniques de descente d'échelle dynamique (grid nesting) ont ensuite été utilisées pour simuler un second épisode de transport avec chute de neige. L'augmentation de la résolution horizontale intensifie les contrastes de vitesse de vent entre versants au vent et sous le vent. En revanche, elle modifie peu les quantités et les structures spatiales des précipitations solides autour du Col du Lac Blanc. Lorsqu'il est activé, le transport devient la principale source d'hétérogénéités des accumulations neigeuses / Blowing and drifting snow are crucial components of the interaction between the cryosphere and the atmosphere. In mountainous areas, it affects the temporal and spatial distribution of snow depth throughout the winter season and influences avalanche formation. Numerical modeling offers a solution for studying the complex interaction between the snowpack and the wind field and to assess the related processes in a spatially distributed way. In this context, this PhD describes the development and the validation of a coupled snow/atmosphere model which is dedicated to the study of blowing and drifting snow in alpine terrain. The coupled model consists in the atmospheric model Meso-NH and the detailed snowpack model Crocus. Blowing and drifting snow have been monitored at the Col du Lac Blanc (Grandes Rousses range, French Alps) experimental site. A database consisting of blowing snow events observed over 10 years allowed us to identify the main features of these events. Numerical simulations using Crocus illustrated the necessity of taking the wind-dependence of snow grain characteristics into account in order to simulate satisfactorily the occurrence of blowing snow events. We also carried out two measurement campaigns at our experimental site in 2011 and 2012 in order to collect validation data for the model. This includes measurements of vertical profiles of wind speed and snow particle fluxes near the surface and the mapping of areas of erosion and deposition using terrestrial laser scanning. The coupled Meso-NH/Crocus model has been developed in order to account for blowing and drifting snow. It simulates snow transport in saltation and in turbulent suspension and includes the sublimation of suspended snow particles. In the atmosphere, a double-moment scheme allows the model to simulate the spatial and temporal evolution of the snow particle size distribution. The implementation of a surface boundary layer scheme at the interface between Meso-NH and Crocus turned out to be necessary to reproduce the strong vertical gradient of snow particle concentration near the surface. Meso-NH/Crocus is the first coupled snow-atmosphere model that can simulate snow transport in alpine terrain in an interactive way.Meso-NH/Crocus has been evaluated against data collected near Col du Lac Blanc during the first measurement campaign in 2011. The simulation of a blowing snow event without concurrent snowfall showed that the model captures the main structures of atmospheric flow in complex terrain, the vertical profile of wind speed and the snow particle fluxes. However, the horizontal resolution of 50 m is found to be insufficient to simulate the location of areas of snow erosion and deposition observed around Col du Lac Blanc. Blowing snow sublimation leads to a reduction in snow deposition of approximately 5%.We used downscaling techniques (grid nesting) to simulate a second blowing event with concurrent snowfall. The increase in horizontal resolution enhanced the contrast of wind speed between windward and leeward slopes. However, it only slightly affects the amount and the spatial pattern of snow precipitation around Col du Lac Blanc. When activated, blowing and drifting snow are the main sources of spatial variability of snow accumulation

The aim of this study was to characterize the wind behavior (velocity, direction, turbulence index and gust factor), as well as a preliminary estimate of the aeolian potential in coastal region close to Maceió. The wind data utilized was collected during the MICROMA project (Micrometeorologia da Mata Atlântica Alagoana) installed at Vilanova Farm, Pilar Alagoas State (9º36 12 S, 35º53 46 W, 170 m), from July/1996 to September/1999. The results showed that the local wind is influenced by micro and macro scale phenomenon. The wind velocity (8,29m height) decreases in the winter and increases in the summer. In the two seasons the wind velocity is faster during daytime. Almost in a half of the case (46%) the wind velocity is between zero and 2,0 m.s-1. The wind direction showed a little variability and the predominant flow is from ocean to continent felt (66%). The behavior of the atmospheric turbulence is inverse to the wind velocity. The wind velocity (estimated to 75m height) in 99,5% of the cases was superior to the initial velocity to start the aero generator (2,5 m.s-1). The simulated average wind power potential value was 110,27±106,51 W.m-2. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho teve como objetivo a caracterização do comportamento do vento (velocidade, direção, índice de turbulência e fator de rajadas), bem como fazer uma estimativa preliminar do potencial eólico para a região de tabuleiros costeiros próximo a Maceió. Foram utilizados os dados de vento coletados durante a realização do projeto MICROMA (Micrometeorologia da Mata Atlântica Alagoana) montado na Fazenda Vilanova, Pilar AL (9º36 12 S, 35º53 46 W, 170 m), no período de julho de 1996 a setembro de 1999. Os resultados mostraram que o vento no local é influenciado pelos fenômenos locais e os de grande escala. A velocidade (8,29 m) diminui no inverno e aumenta no verão, e, em ambas as estações, é bem maior durante o dia. Quase metade (46%) dos casos são ventos na faixa de zero até 2,0 m.s-1. A direção apresenta pouca variabilidade e o fluxo predominante é no sentindo oceano-continente (66%). A turbulência atmosférica é inversamente proporcional a velocidade do vento. O vento estimado para 75m em 99,5% dos casos foi superior a velocidade de partida dos aerogeradores (2,5 m.s-1). O valor médio estimado para o potencial eólico foi de 110,27±106,51 W.m-2 com maior ocorrência na faixa entre 50-100 W.m-2 (38,6%).

Made available in DSpace on 2015-03-13T17:08:40Z (GMT). No. of bitstreams: 1 VeronicaDA.pdf: 5709097 bytes, checksum: 4074580aee5ec2b7d354ddab1d446e43 (MD5) Previous issue date: 2006-05-19 / This work presents geophysical and geological results obtained in a dunefield located in the east coast of Rio Grande do Norte State, with the aim to recognize the aeolian body depositional geometries to a future geologic modeling of the aeolian petroliferous reservoirs. The research, which was done in blowouts region situated at Nisia Floresta Municipally, included the characterization of external geometries with GPS and internal geometry analysis by GPR. Data was integrated in GoCAD software, where it was possible the three-dimensional characterization and interpretation of the studied deposits. The interpretation of GPR profiling allowed identifying: First-order bounding surfaces that separated the aeolian deposits of the Barreiras Formation rocks; Second-order bounding surfaces, which limit dune generations and Third-order bounding surfaces, a reactivation surface. This classification was based and adapted by the Brookfield (1977) and Kocurek (1996) propose. Four radarfacies was recognized: Radarfacies 1, progradational reflectors correlated to foresets of the dunes, Radarfacies 2, plain parallels reflectors related to sand sheets, Radarfacies 3, plain parallels reflectors associated to reworking of the blowout dune crest and Radarfacies 4, mounded reflectors associated to vegetated mound of sand or objects buried in subsurface. The GPR and GPS methods was also employed to the monitoring of dunefields susceptible to human activities in Buzios Beach, where the constructions along the blowout region and the tourism are changing the natural evolution of the deposits. This fact possibly to cause negative impacts to the coastal zone. Data obtained in Dunas Park, a unit environmental conservation, was compared with information of the Buzios Beach. There is a major tendency of erosion in Buzios, specifically in blowout corridor and blowout dune / Este trabalho apresenta os resultados geol?gicos e geof?sicos obtidos em um campo de dunas situados no litoral oriental do Rio Grande do Norte e teve como objetivo definir as geometrias deposicionais dos corpos e?licos para posterior aplica??o na modelagem geol?gica de campos produtores de ?leo e g?s de origem e?lica. A pesquisa foi realizada em uma regi?o de blowouts, situada no munic?pio de N?sia Floresta - RN, onde foi poss?vel definir a superf?cie externa com o uso do GPS geod?sico e a estrutura??o interna utilizando o GPR (Ground Penetrating Radar). Estes dados foram integrados no software de modelagem geol?gica Gocad, permitindo a visualiza??o tridimensional e interpreta??o dos dep?sitos estudados. O levantamento de perfis geof?sicos permitiu a investiga??o da geometria interna dos dep?sitos, nos quais foi poss?vel reconhecer superf?cies limitantes de 1? ordem (superf?cie deposicional que separa os dep?sitos e?licos de rochas da Forma??o Barreiras), 2? ordem (superf?cie que separa diferentes pulsos de sedimenta??o e?lica) e 3? ordem (superf?cies de reativa??o). A classifica??o destas superf?cies acima descritas foi baseada e modificada das propostas de Brookfield (1977) e Kocurek (1996). Foram ainda definidas quatro radarf?cies, com base na forma e termina??o dos refletores: Radarf?cies 1, representada por refletores progradantes, os quais se relacionam aos foresets das acumula??es e?licas; Radarf?cies 2, que ? constitu?da por refletores suscept?veis ? a??o antr?pica na praia de B?zios, onde constru??es ao longo da regi?o de blowouts e a pr?tica intensiva de turismo est?o modificando o desenvolvimento natural destas acumula??es e?licas, podendo gerar impactos ambientais negativos para a zona costeira. Dados obtidos numa ?rea situada no Parque das Dunas (unidade de conserva??o ambiental) foram utilizados para compara??o com as informa??es adquiridas em B?zios. H? uma tend?ncia maior de eros?o na ?rea de B?zios, notadamente no corredor do blowout e na duna de blowout

The aim of this study was to map the prevalence of aeolian sand dunes in Västerbotten, northern Sweden to find dunes formed during earlier deglaciation phases, which was then preserved in cold-based conditions during the youngest stadial of the Weichselian glaciation. These preserved dunes were expected to be covered by a layer of till and have a rather faint morphology compared to dunes formed during the Holocene. Consequently, high resolution LIDAR-derived images from the Swedish mapping, cadastral and land registration authority (Lantmäteriet) was used to detect the dunes throughout an area covering most of Västerbotten, above the highest coastline and below the mountain range. The analysis resulted in several new findings of aeolian dunes compared to the findings in the quaternary soil map created by the Geological Survey of Sweden. Despite the fact some of the dunes at the LIDAR-derived image had a strange faint appearance, it was quickly evident during the fieldwork that the aeolian sand was not covered by till on any of the dunes visited. The common view during the last decades has been that cold-based ice will not erode or alter the morphology of the landscape beneath the ice. However, this study suggests that hypothesis may not be entirely correct, and therefore it can be hard to use geomorphological implications to reconstruct past glacial environments. Thus, it can be concluded that even under cold-based conditions, preservation of aeolian sand dunes in Västerbotten is probably not very common.

Orientador: Edgardo Manuel Latrubesse / Resumo: Compreender a evolução paleoclimática do Quaternário na região Nordeste do Brasil (NEB) é parte fundamental para entender como tem funcionado a circulação atmosférica na faixa tropical da América do Sul. Nesse contexto, o campo de dunas eólicas estabilizadas do Médio Rio São Francisco é um “geoproxy” de grande potencial principalmente por fornecer informações sobre o comportamento dos paleoventos durante os estágios de formação e desenvolvimento das dunas eólicas presentes nesta região. A magnitude e tipo das dunas arenosas presentes neste campo eólico são características particulares desta área em relação a outros registros eólicos da América do Sul tropical. Assim, o principal objetivo deste trabalho é propor um modelo de organização espacial dos padrões eólicos predominantes, inferir mecanismos de desencadeamento e expansão do campo de dunas, e contribuir com o entendimento paleoclimático do NEB a partir de resultados de datações por luminescência optica dos principais padrões de dunas eólicas integrados com outros dados proxies da região. Baseado na combinação de métodos de sensoriamento remoto, morfoestratigrafia e datação por luminescência óptica, definimos as unidades morfosedimentares do campo eólico e, secundariamente, da planície aluvial do Rio São Francisco. Devido a pouca informação de subsuperfície, analisamos dados prévios da planície flúvio-eólica com objetivo de entender a estruturação do arcabouço no qual ocorreu a expansão do campo eólico. Usamos mapa prévio... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The paleoclimatic knowledge of the Quaternary period of Northeastern Brazil (NEB) is key to understanding how atmospheric circulation has worked in the tropical zone of South America. In this context, the inactive dune field in the Middle São Francisco River is a “geoproxy” of great potential mainly because it provides information on the behavior of paleowinds during the formation and development stages of the aeolian dunes present in this region. The magnitude and type of sandy dunes present in this dune field are particular characteristics of this area in relation to other wind records in tropical South America. Thus, the main objective of this work is to propose a model of spatial organization of the prevailing aeolian patterns, to infer mechanisms of triggering and expansion of the dune field, and to contribute to the paleoclimatic understanding of NEB from results of dating by optical luminescence of the main patterns aeolian dunes integrated with other proxies data from the region. Based on the combination of remote sensing, morphostratigraphy and optical luminescence dating, were define the morphosedimentary units of the dunefield, and secondarily of the alluvial plain of the São Francisco River. Due to scarcity of subsurface information, we analyzed previous data from the fluvial-aeolian plain in order to understand the structure of the framework in which the expansion of the dunefield occurred. Were used a previous map derived from magnetic anomaly data, sedimentary ... (Complete abstract click electronic access below) / Doutor

Les effets taphonomiques spécifiques de l'abrasion éolienne à long terme sur les os sont encore mal compris. Afin de mieux comprendre ce processus et sa capacité à créer des pseudo-outils, nous avons abrasé expérimentalement des fragments d'os longs d'ongulés dans des conditions de laboratoire. La reconnaissance croissante, au cours des dernières années, que les outils en os non modifiés sont une partie intégrale de la culture matérielle des êtres humains du passé, et constituent un objet d'étude valable, a conduit à un besoin accru de comprendre si des phénomènes naturels peuvent produire des objets similaires. Une soufflerie ayant la capacité de transporter du sédiment a été utilisée pour étudier l'impact de l'abrasion éolienne sur les surfaces des os. Différentes tailles de sédiments et vitesses de vent ont été testées. L'évolution qualitative de l'os a été documentée pendant un maximum de 250 heures d'abrasion éolienne. Une nouvelle méthode de quantification des polis et autres modifications de surface a été développée en utilisant les paramètres de rugosité de surface tels que définis par la norme ISO 25178. Ils sont appliqués ici pour mesurer et distinguer le polissage éolien et anthropique. Un polissage mat uniforme ainsi qu'un arrondissement important des rebords sont les deux modifications les plus fréquemment observées. Les stries ou fissures visibles sur les os non modifiés sont devenues moins apparentes avec le temps. La masse des spécimens a été suivie pendant les expériences afin de calculer le taux d'abrasion et d'établir une base quantitative pour étudier comment différentes conditions sédimentologiques et atmosphériques peuvent modifier les os. Nos résultats suggèrent que la vitesse du vent est un facteur plus important que la taille des sédiments pour déterminer l'intensité des modifications et le taux d'abrasion. Les résultats ont été comparés à des outils en os créés expérimentalement, fabriqués et utilisés pour une étude précédente. Les traces d’usures sur les outils se distinguaient, qualitativement et quantitativement, des modifications éoliennes. Cette recherche a de nombreuses implications pour l'étude des traces d’usure sur des os non modifiés provenant de contextes archéologiques et l’abrasion éolienne en tant qu'agent taphonomique primaire ou secondaire, ainsi que pour la formation de sites en contexte arides et venteux. / The specific taphonomic effects on bones of long-term aeolian abrasion are still poorly understood. In order to gain a better understanding of this process and its capacity to create pseudo-tools, we have experimentally abraded large ungulate long-bone fragments in laboratory conditions. The growing recognition, over the last few years, that unmodified bone tools are an integral part of past human material culture, and a valid object of study has led to an increased need for understanding if natural phenomena can produce similar objects. A wind tunnel with the capacity to transport sediment was used to study the impact of wind abrasion on bone surfaces. Different sediments sizes and wind speeds were tested. The qualitative evolution of the bone was documented during a maximum of 250 heures of aeolian abrasion. A novel method of quantifying polishes and other surface modifications was developed using surface roughness parameters as defined by ISO 25178. They are applied here to measure and distinguish aeolian and anthropogenic polishing. A uniform matte polish as well as significant edge rounding were the two most common modifications observed. Any striations or fissures visible on the unmodified bones became less apparent over time. The mass of the specimens was tracked during the experiments to calculate the abrasion rate and establish a quantitative base line for studying how different sedimentological and atmospheric conditions can modify bones. Our results suggest that wind speed is a more important factor than sediment size in determining the intensity of modifications and abrasion rate. The results were compared to experimentally created bones tools fabricated and used for a previous study. Tool manufacture and use-wear were distinguishable, both qualitatively and quantitatively, from aeolian modifications. This research has numerous implications for the study of use-wear on unmodified bone from archaeological contexts, aeolian abrasion as a primary or secondary taphonomic agent as well as on site formation in arid windy environments.

Aeolian dust that gets deposited builds up loess sequences that cover 10% of the Earth's continents. Such sequences can be several metres thick with material deposited over thousands of years, and therefore act like archives of past climates. The glacial and interglacial cycles during the late Quaternary affects the loess deposition and the dust in the atmosphere, which has an impact on the global climate. Loess material is deposited during colder and drier periods. Paleosols have often been developed in the loess sequences, reflecting a warmer and wetter climate with decreased dust deposition. By sampling loess from different depths of the sequence and analysing different properties of the material, a reconstruction of past environment and climate can be done. Two commonly used methods are magnetic susceptibility analysis and grain size analysis and differences in the result can show differences in the climate and environment at the time the material was deposited. The late Quaternary climate was influenced by changes in the North Atlantic, and loess in the area is important to study to get a better understanding of the climate at the time it was deposited. In this project, loess material from a 10 metres thick sequence at the Romont site, Belgium has been analysed with grain size and magnetic susceptibility measurements to reconstruct past climate. The results show differences in the magnetic enhancement and the grain size as a gradual decrease in the magnetic enhancement, indicating a colder climate as confirmed by an increase in the U-ratio. This is followed by the abrupt onset of the warm Holocene period, matching the marine isotope record at the approximate same time period. The magnetic susceptibility data identifies the Rocourt tephra layer and also shows evidence of erosion of material between the Kincamp soil and the Nagelbeek Tongue Horizon. / Fint sandmaterial som transporteras med vinden kallas för stoft, när det sedan avsätts på marken bygger det upp så kallade för löss-sekvenser. En löss-sekvens kan vara flera meter tjock och uppbyggd under tusentals år, vilket innebär att materialet på olika djup reflekterar hur klimatet var då det avsattes. Klimatet under senkvartär tid reflekterar istider och mellanistider, vilket påverkar mängden stoft i atmosfären och avsättningen av materialet. Materialet har främst avsatts under kalla och torra perioder. Avsättningen minskade under varma och blöta perioder, vilket var optimalt för så kallade  paleosoler att bildas genom vittring. Genom att ta prover från olika djup i en löss-sekvens och analysera dem är det möjligt att tolka tidigare förändringar i klimatet. Två vanliga analysmetoder är att mäta materialets magnetiska mottaglighet och kornstorleken på materialet. Klimatet under senkvartär tid (130 - 12 tusen år sedan) påverkades av norra Atlanten. Det är därför av stor vikt att analysera prover från platser i närheten, för att bättre förstå hur klimatet varierat då materialet avsattes. I det här projektet har material från en 10 meter tjock löss-sekvens i Romont, Belgien analyserats. Resultatet visar variationer i kornstorlek och magnetisk mottaglighet. Ett vulkaniskt lager som kallas Rocourt identifierades, följt av en gradvis minskning av den magnetiska mottagligheten som visar på ett gradvis kallare klimat fram till början på den varma Holocen-perioden som vi befinner oss i nu. Resultatet visar också bevis för erosion mellan två enheter i sekvensen.

This dissertation combines studies of aeolian bedforms and aeolian dune-field patterns to create a comprehensive set of tools that can be used in tandem (or separately) to extract information about climate change and landscape evolution, and to identify the controls on formation for specific modern dune fields or ancient aeolian sequences. The spatial distribution of surface processes, erosion/deposition rates, and lee face sorting on aeolian dunes are each a function of the incident angle. This correlation between stratification style and incidence angle can be used to develop a “toolbox” of methods based on measurements of key suites of parameters found in ancient aeolian deposits. Information obtained from the rock record can be used as input data for different kinds of numerical models. Regional-scale paleowind conditions can be used to validate paleoclimate and global circulation models. Understanding the natural variability in the Earth’s climate throughout its history can help predict future climate change. Reconstructed wind regimes and bedform morphologies can be used in numerical models of aeolian dune-field pattern evolution to simulate patterns analogous to those reconstructed from ancient aeolian systems. Much of the diversity of aeolian dune-field patterns seen in the real world is a function of the sediment supply and transport capacity, which in turn determine the sediment availability of the system. Knowledge of the sediment supply, availability, and transport capacity of aeolian systems can be used to predict the amount of sand in the system and where it might have migrated. This information can be extremely useful for development and production of oil and gas accumulations, where a discovery has been made but the spatial extent of the aeolian reservoir is unknown. / text

Le vieillissement des lignes de transport d’énergie électrique est une problématique majeure des réseaux. D’ailleurs, des problèmes se posent au plan de l’évaluation de l’état des conducteurs qui, soumis aux vibrations éoliennes, sont vulnérables à l’endommagement en fatigue. Surtout présent aux pinces de suspension, ce phénomène est encore difficile à quantifier, notamment quant à la prédiction de la durée de vie résiduelle des conducteurs. D’autre part, avec le besoin croissant d’optimiser l’exploitation du réseau tout en maintenant sa fiabilité, une estimation précise de l’état d’endommagement des conducteurs est primordiale. Pour cela, une caractérisation des sollicitations à l’échelle des brins est d’abord requise. L’objectif principal de cette thèse vise donc le développement d’une stratégie de modélisation et d’analyse des conducteurs sollicités en vibrations éoliennes permettant une évaluation précise des conditions de chargement locales à l’échelle des brins, tout en tenant compte de l’effet de la géométrie des pinces de suspension. Une stratégie de modélisation 3D des solides toronnés est d’abord développée avec la méthode des éléments finis selon une discrétisation individuelle des brins par éléments poutres, capable de traiter toutes les interactions inter-filaires en frottement. Cette modélisation traduit efficacement la cinématique des torons tout en donnant accès aux charges locales. Son caractère général lui permet aussi d’être appliquée à tout problème impliquant des torons. Appliquée à l’étude des conducteurs sous l’effet des vibrations éoliennes, la stratégie conduit à une description précise de leur comportement tant au plan global en flexion que de la description des contraintes aux brins. Des estimations réalistes de durées de vie en fatigue des conducteurs sont même possibles par l’application de critères d’endommagement aux contraintes. Ensuite, les pinces de suspension sont intégrées à la stratégie de modélisation selon une représentation surfacique traitant le contact pince/conducteur. Une comparaison à des mesures expérimentales met en relief la précision de l’approche. L’analyse de la solution numérique permet l’identification des zones critiques d’endommagement en contact à chacune des couches du conducteur et révèle des informations nouvelles quant à la nature de la sollicitation des brins à la pince de suspension. Finalement, des travaux exploratoires proposent un nouveau concept d’analyse multi-échelles en combinant la modélisation numérique d’un système pince/conducteur à des essais de fatigue sur brins individuels. Une mise en œuvre préliminaire de l’approche permet de valider le concept et en jette les bases en vue de son application future. En somme, la stratégie de modélisation développée dans cette thèse constitue un puissant outil d’analyse qui ouvre maintenant la voie à une caractérisation appropriée de la fatigue des conducteurs en vue ultimement de prédire leur durée et vie résiduelle. / Abstract : The aging of overhead transmission lines is a major concern for utilities. In particular, problems arise in assessing the integrity of conductors whose exposure to Aeolian vibrations renders them vulnerable to fatigue damage. Occurring mainly at the suspension clamps, conductor fatigue is still difficult to quantify, especially regarding the prediction of their residual life. With the increasing need to optimize the power grid while maintaining its reliability, accurate evaluations of the conductor damage state become crucial. To this matter, a characterization of the stress levels at the wire scale is first required. The main objective of this thesis is therefore to develop a strategy for the modeling and analysis of conductors subjected to wind induced vibrations, allowing an accurate description of the local load conditions, while accounting for the effects of the suspension clamps. A finite element wire strand modeling strategy is first developed based on a 3D beam element discretization, considering all frictional wire interactions. The modeling approach efficiently reproduces the wire strand kinematics while giving access to the local loads. Its general formulation also allows it to be applied to any problem involving strands. Applied to the study of conductors subjected to Aeolian vibrations, the strategy leads to an accurate description of their behavior at both the global strand deformations and the wire stress description. Realistic conductor residual life estimates are even possible with the use of common damage criteria. The suspension clamps are then incorporated into the modeling strategy using a surface representation of the conductor/clamp contact. Comparisons with experimental measurements highlight the precision of the approach. The model response analysis allows now the identification of the critical damage zones within each conductor layers and reveals new information about the nature of the wire stresses at the suspension clamp. Finally, exploratory works propose a new concept of multi-scale analysis combining the numerical conductor/clamp modeling strategy to experimental fatigue tests on individual wires. A preliminary implementation of the approach validates the concept and lays the foundations for its future application. In summary, the modeling strategy developed in this thesis constitutes a powerful analytical tool which now opens the way to an appropriate characterization of conductor fatigue with the ultimate objective to eventually predict their residual life.

La direction des vents nourriciers, obtenue à partir des gradients granulométriques et des morphologies dunaires, semble avoir changé au cours du temps. Celle-ci est orientée O-E au Pléniglaciaire moyen, puis NO-SE au Pléniglaciaire supérieur, tandis qu’au Dryas récent la direction est plutôt SSO-NNE. Dans ce travail, l’hypothèse d’un changement de la saison à laquelle les sables sont remobilisés est privilégiée. Ainsi, par comparaison avec la distribution azimutale actuelle des vents à l’échelle de l’année et en accord avec les reconstitutions pour le LGM, il est suggéré qu’au Pléniglaciaire supérieur la déflation éolienne était décalée vers la saison estivale, c’est-à-dire après la phase de dégel des sols et de fonte de la neige. Au contraire, les orientations établies pour le Pléniglaciaire moyen et le Dyras récent refléteraient une déflation active en période hivernale. / Le Pleniglacial, the north-west during the Upper Pleniglacial, and from south-southwest throughout the Younger Dryas. Here, we connect changing wind directions to seasonal variations in aeolian transport. Comparing annual azimuthal distribution of current wind regimes with wind regime models for LGM suggests that during the Upper Pleniglacial the dominant aeolian transport season shifted towards the summer, i.e. after seasonally frozen ground thawed and snow cover melted. Conversely, Middle Pleniglacial and Younger Dryas wind regimes reflect a general deflation during the winter.