Transonic Static Aeroelasticity Using the 2.5D Nonlinear Vortex Lattice Method

RÉSUMÉ Ce mémoire traite de l’évaluation aéroélastique d’ailes peu et très flexibles dans le régime subsonique et transsonique. L’objectif de ce travail est de développer un outil d’aéroélasticité statique pour l’optimisation en phase conceptuelle et préliminaire, capable d’être utilisé en milieu industriel dans lequel les logiciels aérodynamique et de mécanique solide sont en toute probabilité différents. Le grand nombre d’itérations qui doivent être évaluées pour explorer l’espace d’optimisation impose une contrainte de faible coût de calcul. Pour atteindre cet objectif, une méthode potentielle linéaire Vortex-Lattice, combinée avec des données 2.5D RANS à l’aide d’une méthode de couplage alpha modifiée est couplée grâce à une méthode ségrégée avec un modèle d’éléments finis à petites déformations, mais grande déflexions composé de poutres Euler-Bernoulli. Les maillages fluides et solides étant très différents, une méthode d’interpolation conservative est utilisée pour transférer les forces aérodynamiques et les déformations de la structures. Ces transferts d’informations se font de manière consécutive suite aux solutions numériques individuelles du fluide et de la structure. Ce processus est répété itérativement jusqu’à l’atteinte d’une solution convergée. D’abord, le solveur d’éléments finis développé pour les calculs de structure est décrit. Sa précision est par la suite vérifiée pour des cas géométriquement non linéaires statiques et dynamiques. En deuxième lieu, la précision du couplage inviscide par méthode ségrégée est vérifiée en comparant les déformations pour le cas subsonique pour des ailes à grand élancement. En troisième lieu, la précision du couplage visqueux par méthode ségrégée est vérifiée pour le cas subsonique pour des ailes à grand élancement. Cette méthode est par la suite appliquée et validée pour un cas transsonique en comparant avec des solutions 3D RANS numériques publiées précédemment pour le modèle de soufflerie du Common Research Model. Les résultats démontrent que la précision est intéressante pour la prédiction des déformations et des distributions de pression, à un coût de calcul approprié pour les phases conceptuelles et préliminaires d’aéronefs. Finalement, les limites de la méthode et des avenues de recherches sont présentées.----------ABSTRACT This thesis deals with the static aeroelastic evaluation of subsonic and transonic aircraft wings experiencing mild to large deflections. The objective of the work is to develop a static aeroelastic tool for conceptual and preliminary design optimization, capable of performing this task within an industrial environment where computational solvers are likely to be separate for aerodynamic and structural purposes. The high number of design iterations that are necessary to explore the optimization design space requires that the computational cost of the method be low. To this end, a linear potential vortex lattice method combined with 2.5D RANS sectional data through a modified alpha coupling method is coupled to a finite element model consisting of linear Euler-Bernoulli beams in a partitioned fashion. There being a significant mismatch between the aerodynamic meshes and the structure meshes, the aeroelastic coupling uses a conservative interpolation method to transfer the aerodynamic forces and structural deflections between fluid and structural solvers. This procedure is repeated iteratively until a converged coupled solution has been obtained. Firstly, the finite element solver developed for the structural computations is detailed. The accuracy of this solver is subsequently verified for static and dynamic geometrically nonlinear cases. Secondly, the accuracy of the inviscid partitioned coupling is verified by comparing subsonic deflections for large aspect ratio wings with comparable methods that have previously been published. The results show that the method performs well in predicting the deflections of high aspect ratio wings. Thirdly, the accuracy of the viscous partitioned coupling is verified for large aspect ratio wings in the subsonic regime. The method is then applied in the transonic flight regime by comparing it with 3D RANS computation results previously published for the Common Research Model wind tunnel model. The results show impressive accuracy in predicting the wing deflections and pressure distributions, at a computational cost that is appropriate for conceptual and preliminary design. Finally, limitations and possible avenues for research are presented

Rare birds of prey observations in Kresna Gorge in Bulgaria

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Five years overview of the reintroduction of Griffon Vulture Gyps fulvus in Kresna Gorge, Bulgaria

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Heavy metals in bones from Harbour Porpoises Phocoena phocoena from the Western Black Sea Coast

During the last few years, the Western Black Sea coast has documented increase in the number of stranded marine mammals, particularly the harbour porpoise (Phocoena phocoena). This species is a subject to threats such as exposure to contaminants, fishery by-catch and introduced new marine species. The aim of this study was to analyse spatial and age trends in bone metal concentration in harbour porpoises from the Western Black Sea Coast. Selected heavy metals (Cu, Pb, Zn, Cd and Ni) were measured in bones of 33 harbour porpoises stranded along the Bulgarian Black Sea Coast from 2017. Spatially, we found higher metal levels in the harbour porpoises stranded in the Northern region compared with those from Southern region. The effect of aging was evident only for Zn content – the levels were higher in juveniles than in adults. The obtained results suggested that heavy metal contamination represent an important threat encountered by harbour porpoises

Cetacean mortality along the Bulgarian Black Sea Coast during 2017

The present study provides information on the stranding of cetaceans along the Bulgarian Black Sea Coast during 2017. Observations were made trough covering transects along the Bulgarian Black Sea Coast. A total of 198 cetaceans of three species were found - Harbor Porpoise (Phocoena phocoena), Bottlenose Dolphin (Tursiops truncatus), and Common Dolphin (Delphinus delphis). The most numerous were the harbor porpoise - 48% followed by the bottlenose dolphin - 15% and common dolphin - 8%. The most significant number of strandings was observed during July and August (54% of all cases). Cetacean strandings events were relatively highly concentrated in the area of Shabla, Varna and Pomorie

Hotspots in the grid: Avian sensitivity and vulnerability to collision risk from energy infrastructure interactions in Europe and North Africa

Wind turbines and power lines can cause bird mortality due to collision or electrocution. The biodiversity impacts of energy infrastructure (EI) can be minimised through effective landscape-scale planning and mitigation. The identification of high-vulnerability areas is urgently needed to assess potential cumulative impacts of EI while supporting the transition to zero carbon energy. We collected GPS location data from 1,454 birds from 27 species susceptible to collision within Europe and North Africa and identified areas where tracked birds are most at risk of colliding with existing EI. Sensitivity to EI development was estimated for wind turbines and power lines by calculating the proportion of GPS flight locations at heights where birds were at risk of collision and accounting for species' specific susceptibility to collision. We mapped the maximum collision sensitivity value obtained across all species, in each 5 × 5 km grid cell, across Europe and North Africa. Vulnerability to collision was obtained by overlaying the sensitivity surfaces with density of wind turbines and transmission power lines. Results: Exposure to risk varied across the 27 species, with some species flying consistently at heights where they risk collision. For areas with sufficient tracking data within Europe and North Africa, 13.6% of the area was classified as high sensitivity to wind turbines and 9.4% was classified as high sensitivity to transmission power lines. Sensitive areas were concentrated within important migratory corridors and along coastlines. Hotspots of vulnerability to collision with wind turbines and transmission power lines (2018 data) were scattered across the study region with highest concentrations occurring in central Europe, near the strait of Gibraltar and the Bosporus in Turkey. Synthesis and applications. We identify the areas of Europe and North Africa that are most sensitive for the specific populations of birds for which sufficient GPS tracking data at high spatial resolution were available. We also map vulnerability hotspots where mitigation at existing EI should be prioritised to reduce collision risks. As tracking data availability improves our method could be applied to more species and areas to help reduce bird-EI conflicts

Tracking data highlight the importance of human-induced mortality for large migratory birds at a flyway scale

Human-induced direct mortality affects huge numbers of birds each year, threatening hundreds of species worldwide. Tracking technologies can be an important tool to investigate temporal and spatial patterns of bird mortality as well as their drivers. We compiled 1704 mortality records from tracking studies across the African-Eurasian flyway for 45 species, including raptors, storks, and cranes, covering the period from 2003 to 2021. Our results show a higher frequency of human-induced causes of mortality than natural causes across taxonomic groups, geographical areas, and age classes. Moreover, we found that the frequency of human-induced mortality remained stable over the study period. From the human-induced mortality events with a known cause (n = 637), three main causes were identified: electrocution (40.5 %), illegal killing (21.7 %), and poisoning (16.3 %). Additionally, combined energy infrastructure-related mortality (i.e., electrocution, power line collision, and wind-farm collision) represented 49 % of all human-induced mortality events. Using a random forest model, the main predictors of human-induced mortality were found to be taxonomic group, geographic location (latitude and longitude), and human footprint index value at the location of mortality. Despite conservation efforts, human drivers of bird mortality in the African-Eurasian flyway do not appear to have declined over the last 15 years for the studied group of species. Results suggest that stronger conservation actions to address these threats across the flyway can reduce their impacts on species. In particular, projected future development of energy infrastructure is a representative example where application of planning, operation, and mitigation measures can enhance bird conservation

Poisoning and re-introduction of the Griffon Vulture Gyps fulvus in Kresna Gorge, Bulgaria 2017

The reintroduction of the Griffon Vulture Gyps fulvus in Kresna Gorge in south-western Bulgaria started in 2010 (Stoynov & Peshev 2011, 2012, 2013, 2014) and is run by the Fund for the Wild Flora and Fauna (FWFF). At present it is part of the project “Vultures Back to LIFE”. The number of wintering Griffon Vultures during the winter season 2016-2017 was a record high: 50 birds with some counts of over 60. About 10 pairs were showing breeding behaviour and at least four eggs were laid, until mid-March 2017 when the largest documented poisoning event of Griffon Vultures in the Balkan Peninsula occurred.From 12 March 2017 to early April of that year, the bodies of 18 Griffon Vultures were found, and the missing and indirectly identified victims numbered more than 30 individuals. Although several cases of poison baits targeted to kill wolves were recorded near the villages of Stara Kresna, Krupnik and Tserovo, all the vultures were poisoned probably in the same place near the village of Tserovo over at least three consecutive stages. While small baits were used in the first two regions and affected mostly wolves, foxes, and dogs, in the area of Tserovo the poison was set in a carcass of a dead cow that remained an active bait on the ground for more than two weeks. Despite the wide media coverage and mass public response to this destruction of nature, law enforcement investigations did not result in any prosecutions.The incident marked 2017 year as a catastrophe for the colony of Griffon Vultures in Kresna Gorge. Birds from other colonies were killed too: several birds from Vrachanski Balkan, including the first marked chick from a nest in the region, a bird from the Eastern Rhodopes and several from Macedonia and Serbia.High levels of management effort, combined with an increasing knowledge of the species and applied by FWFF and related organizations, resulted in the Kresan Gorge colony reconsolidating and being sustained. The remaining five to eight birds, probably with memory of the colony of Kresna Gorge, were supported by the immediate release of six more Griffon Vultures and by the continuous provision of safe food at vulture feeding sites. By the end of 2017, the local group of vultures ranged in size between 15 and 35 birds. For the monitoring and possible prevention of poisoning, the use of precise and intensive data collection via satellite transmitters was introduced

Feeding site usage by griffon vultures (Gyps fulvus) in Bulgaria revealed by camera traps

A group of griffon vultures in Kresna Gorge was studied for its visit on the feeding station next to Rakitna Village after being reintroduced in the area. A camera trap method was used for a better understanding of the breeding behaviour of the griffon vulture, including the intra- and inter-species relations. A statistically significant difference was found between the independent feeding events during the pre-incubation and incubation periods of vultures. The duration of those events also differs, the ones in the second period being longer. Furthermore, a statistically significant difference was observed between the number of vultures per photo for the two sample periods, as a result of a different number of unmarked wild birds and different activity patterns of the nesting pairs. In spite of the fact that the terrestrial predators are also active during the night, their daytime presence leads to a high enough overlap between the two ecological groups, showing that the carnivores are a disturbance factor for the scavengers. The raven is the most abundant species at the feeding site and thus is a food competitor to the griffon vulture. The two species have adapted their behaviour to use the feeding station more successfully during the different biological periods. A significant decrease in the activity overlap between the individuals of the successfully nesting pairs was observed on the feeding station after the beginning of the incubation period. On the other hand, the activity overlap of the unsuccessfully nesting pairs increased in the second sample period. Camera traps can be used in further studies of the mating ecology for individual breeding pairs, when a direct observation on the nest is hard or impossible. This can be a cheap alternative of the time-consuming field observations