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The planetary boundary layer (PBL) is the turbulently most active part of the Earth’s and Martian lower atmospheres. Over the last few decades, high-resolution satellite and in-situ measurements, plus the rapid growth in the massive computing have provided a growing interest in this phenomenon, ranging from weather and climate studies to planetary science applications. Thanks to the ongoing lander and rover missions, in-situ observations of Martian surface processes, such as dust, water and methane transport, have been attracting more attention, especially in to search for the signatures of the planet’s habitability. This highlights the significance of PBL dynamics, which is the primary governor of surface-atmosphere exchange processes on Mars. The PBL, on the other hand, has various physical phenomena associated with a large range of length scales, from planetary scales to microscales. Therefore, the present thesis proposes a series of novel turbulence models in a multiscale framework to advance the current knowledge on the nature of PBL turbulence forming in the atmospheres of Earth and Mars. This study, for the first time, presents a novel scale-aware gray-zone turbulence, fully representing the three-dimensional turbulence fluxes in the so-called "Terra Incognita" range of scales, in which traditional turbulence models become invalid as they were initially designed for their own either mesoscale or microscale limits. Here, the new gray-zone turbulence model offers an advanced framework for bridging the mesoscale and microscale limits that is suitable for the development of next-generation three-dimensional multiscale turbulence models for Earth and Mars. The generic formulation of new turbulence models developed here is extensively applicable to a wide range of terrestrial planetary atmospheres, ranging from Saturn's moon Titan towards terrestrial exoplanets., Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

Ice accretion poses substantial safety hazards for the manned and unmanned aviation industries. Its study is essential for icing events risk assessment and for the development of efficient ice protection systems. The existing ice accretion measurement techniques—casting, molding, and laser-scanning—are time-consuming, sometimes cumbersome to use, and highly expensive, while hand tracing is inexpensive, but has lower accuracy and time-consuming post-processing. This work presents two low-cost, fast, and easy-to-use measurement techniques for 2D ice accretion profiles. Both employ algorithms of automatic ice shape detection, one based on unmediated image-processing, another based on the processing of manual ice tracings. The techniques are applied to ice accretion experiments conducted in an icing wind tunnel at low Reynolds numbers, and their results are validated against ice thickness caliper measurements. A comparison of the results shows that both techniques accurately measure the leading-edge ice thickness and the 2D shape of the ice accretion profiles. One technique is faster, with higher measurement accuracy, but produces interrupted-line 2D ice profiles and requires good lighting conditions, while the other generates continuous-line 2D profiles and has no application restriction, but it is slower, with lower accuracy. A discussion is conducted, aiming to help one determine the best applications for each ice accretion measurement technique presented., SCOPUS: ar.j, info:eu-repo/semantics/published

Ce rapport de thèse a pour but de présenter la conception et la réalisation d'un micro-drone de type Vertical TakeOff and Landing (VTOL) à rotors carénés. Ce dernier a initialement été conçu pour répondre aux exigences d'un concours de micro-drones, organisé par l'ONERA (Office Nationale d’Etudes et de Recherches Aérospatiales) et la DGA française (Délégation Générale pour l’Armement) dont le but est de faire émerger des solutions techniques innovantes. Le concours a pour objet de démontrer la faisabilité technique et l'intérêt opérationnel des micro-drones utilisés lors des opérations militaires dans la progression en milieu hostile. Plus connue sous l'acronyme anglais MAV, pour Micro Air Vehicle, les caractéristiques précises d'un mini ou micro-drone ont beaucoup évoluées au fur et à mesure des avancées technologiques et elles nécessitent d'être définies. Le premier concept qui a été mis au point par l'ULB en 2004 est un drone à rotor caréné à pas variable muni d'un plateau cyclique. Le drone a ensuite évolué vers un mécanisme plus simple doté d'un rotor à pas fixe pour participer à la seconde génération du concours. Issue d'un partenariat avec l'Ecole des Mines d'Alès (EMA), notre équipe Dulbema, après avoir franchi les trois premières épreuves du concours avec succès, a été retenue parmi les huit équipes finalistes.Le Dulbema est conçu pour être capable d'effectuer l'atterrissage et le décollage enposition verticale. Cela offre la possibilité à l'aéronef de pouvoir évoluer en milieu urbain. La présence du carénage améliore considérablement les performances de l'hélice, par rapport à une configuration classique, et protège les personnes exposées au rotor en mouvement. Cette sécurité intrinsèque permettra au drone, une fois stabilisé, d'être utilisé dans le secteur civil avec peu de risque pour les personnes aux alentours.Le Dulbema se base sur un concept innovateur dans le domaine. En effet, la configuration choisie est différente de celles habituelles. Il va de, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

Wind energy has been one of the best options for developing renewable, clean, and sustainable electricity. The development of wind energy projects begin with prospection of suitable sites for wind farms and that process relies on meteorological data. The vast, complex and high altitude land of the Bolivian Andes represent an important challenge for wind energy assessment, mainly due to the scarce knowledge about wind meteorology, and wind turbine performance in the highlands of Bolivia. In this thesis, the performance of wind farms in the highlands of Bolivia was evaluated computing its capacity factor, and wind turbine efficiency. The Weather Research and Forecasting (WRF v3.8.1) model was parameterized, and the re-analysis data MERRA-2 was evaluated for wind energy and power assessment over the Bolivian Andes.The wind farm performance in the highlands of the Bolivian Andes have been analysed in Qollpana wind farm. The yearly capacity factor was between 0.27 and 0.4. The wind turbines behaviour showed higher efficiency at high-wind conditions. The operation and performance of Qollpana wind farm prove the technical capability to implement wind farms in the Bolivian Andes. The WRF model parameterization was focused in the Planetary Boundary Layer (PBL) schemes due to its major impact in the wind speed and the results showed that NOAH (Land surface), RRTMG (Radiation), KAIN (Convective), THOMPSON (Microphysics), and QNSE (PBL) are the best combination of physical schemes for wind speed and wind direction prediction. However, the temperature was under-predicted in the highlands of Bolivia. The MERRA-2 dataset was evaluated for wind speed assessment and compared with WRF simulations at different altitudes along Bolivia. The comparison showed the under-prediction of wind speed by MERRA-2 when the terrain is complex and high. However, the main factor for the under-predicion of wind speed was the complexity of the terrain. The wind power potential in the Bolivian Andes by, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished