Browsing by Issue Date, starting with "2021-12-29"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- Computational study on coaxial nitrogen-hydrogen injection at supercritical conditionsPublication . Magalhães, Leandro; Silva, André; Barata, Jorge M MIn the present work, we perform a computational study on the mixing of nitrogen and hydrogen at supercritical conditions. A coaxial injection configuration is considered where nitrogen is injected through the central post with a hydrogen co-flow. The flow in both injectors as well as in the combustion chamber is considered in the computations. This preliminary version presents the radial density profiles maximum of both species and radial density profiles at selected locations.
- O impacto da infodemia na sociedade da informação e do conhecimentoPublication . Toniolo, Bianca; Ricarte, Élmano; Noronha, Elizângela; Rego, Lénia; Amorim, FranciscaEditores/as: Bianca Persici Toniolo (LabCom - Comunicação e Artes, Universidade da Beira Interior, Portugal); Élmano Ricarte (Instituto de Comunicação da NOVA, Universidade Nova de Lisboa, Portugal); Lénia Rego (Centro de Estudos de Comunicação e Sociedade, Universidade do Minho, Portugal); Francisca Amorim (LabCom - Comunicação e Artes, Universidade da Beira Interior, Portugal); Elizângela Costa de Carvalho Noronha (NOVA Institute of Communication, Universidade de Coimbra, Portugal) Apoio Editorial: Marisa Mourão (Centro de Estudos de Comunicação e Sociedade, Universidade do Minho, Portugal); Mateus Luan Dellarmelin (Centro de Estudos de Comunicação e Sociedade, Universidade do Minho, Portugal); Fábio Jardelino (LabCom - Comunicação e Artes, Universidade da Beira Interior, Portugal)
- Aerial Journey from Portugal to Timor, Macau, India, and Return (1934)Publication . Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, AndréIn the 1920s and 1930s, a group of Portuguese Aviation Pioneers added the name of Portugal to the History of Aviation, essentially by performing Aerial Journeys to Portuguese Colonies. East Timor was an outlier until 1934. Thus, Humberto Amaral da Cruz conceived and designed an Aerial Journey from Portugal to East Timor, Macau, India, and return, with the primary purpose to highlight the country's relevance and consolidation as a colonial power as a demonstration of sovereignty over its most distant domains. With the help of a national public subscription, a government subsidy, and the support of some private entities, he purchases a De Havilland DH. 85 aircraft. Between October 25 and December 21, the pilot, and his mechanic, António Lobato, accomplish their Journey of 42,670 km in 268 hours and 25 minutes. The pilots' reception was apotheotic, with enormous national pride, followed by the feeling of dignity and expansion of the Portuguese Nation. The Journey had a global impact through the massive propaganda effort from distant countries in the Far East and a vast national influence through the rapprochement and consolidation of the Portuguese colonial empire in the most remote places in the World. Humberto da Cruz demonstrated his skills as a pilot, his skill as an officer, and the strength of his upstanding character. In particular, he praised aviation for developing a new era on earth, arguing that Portugal would have to adopt this form of communication between its overseas territories, Brazil, and the rest of the World.
- Centennial 1922–2022: First Transoceanic Flight with Autonomous Aerial NavigationPublication . Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, AndréAlthough the Transoceanic Flights had already piqued the state's attention, the airplane's lack of aerial navigation equipment rendered it unsuitable for this new trend in 1919. Three years later, in 1922, Sacadura Cabral and Gago Coutinho conducted a Transoceanic Flight to demonstrate the autonomy and usefulness of the Sextant with an artificial horizon, in combination with novel air navigation instruments, all handled by a simplified short air navigation method. Unfortunately, due to errors induced by the vertical dynamics associated with the aircraft's speed, the sextant was constantly adjusted to the sea horizon rather than the perfect readings of the artificial horizon. This condition required a search for a suitably clear horizon line, forcing the seaplane's altitude to be often lowered. Furthermore, a few supplementary navigation devices risked their initial autonomous air navigation. Nonetheless, by measuring the size of the wingspan shadow reflected on the ocean's surface, the pilots managed to adjust their expertise to maintain the seaplane on the planned trajectory. Furthermore, this novel and reliable steering method allowed them to perform trigonometric calculations to estimate their height, which was critical in calculating the aircraft's positioning. Thus, the Journey was recognized as a significant milestone in aviation history, ushering the use of the sextant as a key means of air navigation and proving the effectiveness of a revolutionary principle of Coutinho's short methods, never before documented on Astronavigation. Along with the First Transoceanic Flight with Autonomous Aerial Navigation, one of the itineraries featured an 11 ½ hour crossing the Atlantic from Cape Verde to St. Peter and St. Paul Rocks. When it is remembered that they managed to reach this remote and a pretty small destination (a few hundred ft long and the highest point 60 ft above the water) after a flight of nearly 900 nautical miles over the Ocean, it exalts the remarkable feat of the airmen.
- A Machine Learning Approach to Forecasting Turbofan Engine Health Using Real Flight DataPublication . Silva, Fernanda Cavalcante da; Grinet, M.A.V.M.; Silva, AndréThe modern gas turbine engine widely used for aircraft propulsion is a complex integrated system that undergoes deterioration during operation due to the degradation of its gas path components. Turbofan engine-related costs can account for as much as a third of the total aircraft maintenance costs, which have driven the industry to adopt on-condition monitoring. In this work an integrated condition monitoring platform is proposed and developed for performance analysis and prediction. Different machine learning approaches are compared with the application of predicting engine behavior aiming at finding the optimal time for engine removal. The selected models were OLS, ARIMA, NeuralProphet, and Cond-LSTM. Long operating and maintenance history of two mature CF6 turbofan engines were used for the analysis, which allowed for the identification of the impact of different factors on engine performance. These factors were also considered when training the ML models, which resulted in models capable of performing prediction under specified operation and flight conditions. The ML models provided forecasting of the EGT parameter at the take-off phase allowing for predicting gradual performance deterioration under specified operation type. Cond-LSTM is shown to be a reliable tool for forecasting engine EGT with a MAE under 5℃. In addition, forecasting engine performance parameters has shown to be useful for identifying the optimal time for performing important maintenance action, such as engine gas path cleaning. This work has shown that engine removal forecast can be more precise by using sophisticated trend monitoring and advanced ML methods.
- Theoretical and Numerical Analysis of Oscillating Airfoil Including Viscous EffectsPublication . Torres, George Lucas; Camacho, Emanuel; Marques, Flávio D.; Silva, AndréUnsteady airfoils are the way to explore new aerodynamic phenomena which do not appear in ordinarily aeronautical applications. At lower Reynolds numbers, unsteady flow can make way to newer technologies to be implemented in areas such as extraterrestrial exploration. In the present work, the Theodorsen classical unsteady theory and a viscous extension to this model are implemented. Results from those computations are then compared with high fidelity CFD simulations using laminar and turbulent assumptions. Results obtained by using the viscous model indicate a good agreement with CFD data, although there are still some discrepancies at the trailing edge.
- Wing Design and Analysis for Micro Air Vehicle DevelopmentPublication . Ferreira, Rúben; Camacho, Emanuel; Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, AndréNatural flight was always a source of inspiration to human beings, and by observing it, new technologies emerged, especially in bioinspired aerial vehicle design. The main objective of the present work is to experimentally evaluate the influence of the wing shape on their behavior and power consumption. To accomplish that goal, four wings were selected and an experimental rig was developed. Airflow velocities tested ranged from 0 up to 4 m s−1 with four different throttle positions. Flapping frequency and amplitude were obtained from high-speed camera tests and the power consumption of the wings tested was measured. It is observed that amplitude is between 0.12 m and 0.25 m, frequency between 4 and 15 Hz. Regarding power consumption, the design wings presented lower averaged power-to-weight ratio values when compared to BionicBird wings.