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- Numerical Simulation of Twin Impinging Jets in Tandem Through a CrossflowPublication . Vieira, Diana; Barata, Jorge M M; Neves, Fernando M. S. P.; Silva, A. R. R.The flow field of ground vortex generated by twin impinging jets in tandem through a crossflow is numerically studied in detail. Numerical simulation and visualization are presented for two turbulent circular jets emerging into a low velocity cross stream, impinging after on a flat surface perpendicular to the geometrical jet nozzle axis. The numerical study is based in experimental studies done early, so all the features of the experimental flow were maintained when the numerical simulation was performed. The Reynolds number used was based on the jet exit conditions of 43.000-105.000, a jet to crossflow velocity ratio of 22.5-43.8 an impinging height of 20.1 jet diameters and an interject spacing’s of S = 5D and L = 6D. The analysis of the flow was extended to regions and flow conditions for which no measurements have been obtained in last experimental studies, i.e., for velocity ratios of 7.5-60. The numerical results show that for the smallest velocity ratios the jets initially do not mix but remain together in two layers. Three different types of flow regimes were identify, therefore when VSTOL aircrafts operating in ground vicinity, only the regime with strong impingement on ground and with a formation of a ground vortex is relevant. The numerical results allowed to extend the last experimental studies and prove that the deflection of the rear jet is due to the competing influences the wake, the shear layer, the downstream wall jet of the first jet and the crossflow.
- Sacadura Cabral and the Dawn of Portuguese AviationPublication . Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, AndréSacadura Cabral was one of the two Portuguese navigators that crossed by air the South Atlantic in the beginning of the 20th century. From 1901 to 1915 Sacadura was at Mozambique and Angola where he developed geodetic and geographical missions of the greatest importance for Portuguese interest at Africa. With the Great World War requirements as a Navy Officer with 34 years old he decided to serve Portugal at the Aviation. In 1915 he went to France and obtained its pilot license. In 1916 Sacadura returned to Portugal and begun its instructor pilot career. He developed the “path corrector” which he created to compensate the drift caused by wind. In 1922 Sacadura made the First Air cross from Europe to South Atlantic. In 1923 he proposes himself to make an attempt to the First Air Circumnavigation Journey. He developed all its possible efforts to initiate this journey in March of 1924; however some delays had forced him to postpone the journey. Sacadura received important official medals and prizes, including the PhD Honoris Causa from the Universities of Lisbon and Oporto. In 1924 he died before he could carry out its Circumnavigation Air Journey.
- The First Aerial Raid From Portugal to MacauPublication . Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, AndréIn 1920, Brito Pais and Sarmento de Beires tried an unsuccessful flight attempt from Amadora, Lisbon to Madeira Island aboard the airplane Breguet XIV A2, named "Cavaleiro Negro". Despite the scarce means of navigation they reach Madeira, which failed to land due to dense fog. On the way back after 8 hours of flight time, they alight at the Atlantic Ocean for lack of fuel and were rescued at about 500 km from Lisbon. In 1922, Gago Coutinho and Sacadura Cabral conducted the First Aerial Cross of the South Atlantic, flying from Lisbon to Rio de Janeiro. The Portuguese Aeronautics rejoiced auspicious days that time, with its aviation pioneers trying consecutively to reach more distant places along intercontinental flights. In 1923 Gago Coutinho and Sacadura Cabral were contemplating to perform an Around the World Flight. However, Sacadura died in 1924, while piloting an airplane acquired for the circumnavigation voyage. Also in 1924 the pilots Brito Pais and Sarmento de Beires idealized the conducting of a trip to Macau as an aspiration for a future Portuguese Around the World Flight attempt. On 7 April 1924, those pilots departed from Vila Nova de Milfontes in a Breguet XVI Bn2 airplane, beginning a trip to Macau. On 7 May an engine failure forced them to crash in India. On 30 May they managed to continue the Voyage in a De Havilland DH9 aircraft before being forced to end their attempt in 20 June in flying over Macau. A typhoon hindered their efforts to land and the airplane was crash landed in Chinese Territory about 800 meters from the Hong Kong Border. On 25 June 1924, they were shuttled back to Macau by boat. Brito Pais, Sarmento de Beires and Manuel Gouveia returned to Portugal, via North America, visiting several Portugueses nuclei at China, Japan, United States and England. They went to Portugal on 9 September, after having flown a total of 16760 kilometers in 117: 41h facing often extremely adverse atmospheric conditions, sandstorms and inaccurate navigation maps.
- Twenty-Five Years of Portuguese Aviation Events at AmadoraPublication . Neves, Fernando M. S. P.; Barata, Jorge M M; Silva, A. R. R.From 1912 to 1938, the Amadora became the central location for several of Portugal's most significant aviation events. After a Kite-Flying Competition (1912), Flying Demonstrations (1913), and the 1st Air Festival in Portugal (1917), in 1919, the village became selected to host the Military Aviation Squadron GEAR - Grupo de Esquadrilhas de Aviação «República.» As WWI ended, Aviation shifted its vision to new dimensions of international civil transport. With their minds set on developing Portuguese Civil Aviation, the GEAR pilots started using military aircraft for civilian flight purposes. Thus, between 1920 and 1936, memorable and significant flights departed from Amadora to the most varied Portuguese territories worldwide; 1) Amadora – Madeira Flight Attempt (1920); 2) First Aerial Raid from Portugal to Macau (1924); 3) Amadora – Guinea (1925); 4) A Trailblazing Flight for Portuguese Overseas Commercial Air Route (1928); 5) Amadora – Portuguese India (1930); 6) Round trip Flight Amadora – Guinea – Angola (1930/31); 7) Aerial Journey from Portugal to East Timor, Macau, India, and Return (1934); and 8) Portuguese Empire Mission Amadora – Angola – Mozambique (1935/36). Furthermore, in 1934 and 1935, Amadora received the two firsts International Air Festivals in Portugal. Finally, after nearly Twenty-Five Years of Portuguese Aviation Events in Amadora, Military Aeronautics ended Amadora's connection to national aviation in 1938, thus dictating the end of the Portuguese Pioneer Flights. Organizational reasons, in addition to the smallness and deficiencies of the dirt runway track, determined the extinction of the Grupo de Aviação de Informação n.º 1 [as the GEAR was renamed], whose personnel and material would be later transferred to Tancos.
- Twin Impinging Jets Through a CrossflowPublication . Barata, Jorge M M; Neves, Fernando M. S. P.; Vieira, Diana; Silva, AndréLaser Doppler measurements provide information on the flowfield created by twin impinging jets aligned with a low velocity crossflow. The experiments were carried out for a Reynolds number based on the jet exit conditions of Re j=4.3×104, an impingement height of 20.1 jet diameters and for a velocity ratio between the jet exit and the crossflow V R=Vj/Uo of 22.5, and an interjet spacing of S=6D. The results show a large penetration of the first (upstream) jet that is deflected by the crossflow and impinges on the ground, giving rise to a ground vortex due to the collision of the radial wall and the crossflow that wraps around the impinging point like a scarf. The second jet (located downstream) it is not so affected by the crossflow in terms of deflection, but due to the downstream wall jet that flows radially from the impinging point of the first jet it does not reach the ground. The results indicate a new flow pattern not yet reported so far, that for a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced under pressures in the aft part of the aircraft causing a suction down force and a change of the pitching moment towards the ground.
- Effects of a Dynamic Leading Edge on a Plunging AirfoilPublication . Camacho, Emanuel; Neves, Fernando M. S. P.; Marques, Flávio D.; Barata, Jorge M M; Silva, AndréThe dynamics of oscillating airfoils are of great interest in many research areas such as rotor dynamics and biomimetics. The results reported in this research provide an insight into the mechanics of birds’ leading edge and how the dynamic curvature of the airfoil can highly benefit the aerodynamic and propulsive performance, especially at high angles of attack. The main goal of the current work is to numerically investigate the influence of a deflecting leading edge on the propulsive coefficients and flowfield created by a plunging airfoil at a Reynolds number of 1.4 × 104 and a constant Strouhal number of 0.15 with different ( k, ℎ) combinations. Employing a RANS approach with the proposed NACA0012-IK30 airfoil, results show that dynamically deflecting the leading edge significantly improves the propulsive efficiency of the airfoil by either reducing the required power or improving the thrust production. The outcomes regarding the propulsive efficiency show a considerable increase of up to 92% when the higher nondimensional amplitude was considered.
- Plunging Airfoil: Reynolds Number and Angle of Attack EffectsPublication . Camacho, E. A. R.; Neves, Fernando M. S. P.; Silva, André; Barata, Jorge M. M.Natural flight has consistently been the wellspring of many creative minds, yet recreating the propulsive systems of natural flyers is quite hard and challenging. Regarding propulsive systems design, biomimetics offers a wide variety of solutions that can be applied at low Reynolds numbers, achieving high performance and maneuverability systems. The main goal of the current work is to computationally investigate the thrust-power intricacies while operating at different Reynolds numbers, reduced frequencies, nondimensional amplitudes, and mean angles of attack of the oscillatory motion of a NACA0012 airfoil. Simulations are performed utilizing a RANS (Reynolds Averaged Navier-Stokes) approach for a Reynolds number between 8.5×10^3 and 3.4×10^4, reduced frequencies within 1 and 5, and Strouhal numbers from 0.1 to 0.4. The influence of the mean angle-of-attack is also studied in the range of 0º to 10º. The outcomes show ideal operational conditions for the diverse Reynolds numbers, and results regarding thrust-power correlations and the influence of the mean angle-of-attack on the aerodynamic coefficients and the propulsive efficiency are widely explored.
- Book of abstracts: 4th EJIL LAETA Young Researchers MeetingPublication . Silva, André; Neves, Fernando M. S. P.; Moleira, Filipa; Quental, Carlos; Belinha, Jorge; Arteiro, Albertinho; Almeida, MiguelThe 4th LAETA Young Researchers Meeting (4EJIL 4º Encontro de Jovens Investigadores do LAETA) is held from November, 9th to 10th of 2017 in Covilhã, Portugal. Since its beginning, the EJIL is a continuous source of sharing state-of-the-art developments in the scientific and technological fields of Energy, Transports and Aeronautics and a large number of applications in the field of Mechanical Engineering. This meeting also offers a unique opportunity for joining young researchers of LAETA (Laboratório Associado de Energia, Transportes e Aeronáutica) units, namely: IDMEC, INEGI, ADAI, and AeroG. One main objective of this meeting is the promotion and encouragement of interdisciplinary discussions among young researchers. This Book of Abstracts contains the synthesis of the papers accepted for oral presentation and is organized by the Thematic Research Lines of LAETA, which cover the research fields of Energy, Aeronautics and Space, Advanced Manufacturing, Advanced Materials, Biomechanics, Fires, Engineering Design and Engineering Systems. On behalf of the Organizing Committee, I would like to express our gratitude to those who contributed to the success of this meeting. The assistance provided by the Advisory Committee is highly appreciated. A special thanks also goes to the participants and the authors, without whom the 4EJIL, and this book, would not be possible. And last, but not least, I would like to manifest my sincere gratitude to my colleagues of the Organizing Committee not only for the efficient work performed but especially for the friendly and helpfulness environment lived during the time of preparation of the meeting.
- 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.
- Experimental Study of Two Impinging Jets Aligned With a CrossflowPublication . Barata, Jorge M M; Neves, Fernando M. S. P.; Vieira, Diana; Silva, AndréLaser Doppler measurements provide information on the flowfield created by twin impinging jets aligned with a low velocity crossflow. The experiments were carried out for a Reynolds number based on the jet exit conditions of Rej = 4.3 × 104, an impingement height of 20.1 jet diameters and for a velocity ratio between the jet exit and the crossflow VR = Vj/Uo of 22.5, and an inter-jet spacing of S = 6D. The results show a large penetration of the first (upstream) jet that is deflected by the crossflow and impinges on the ground, giving rise to a ground vortex due to the collision of the radial wall and the crossflow that wraps around the impinging point like a scarf. The second jet (located downstream) is not so affected by the crossflow in terms of deflection, but due to the downstream wall jet that flows radially from the impinging point of the first jet it does not reach the ground. The results indicate a new flow pattern not yet reported so far, that is most relevant for a VSTOL aircraft operating in ground vicinity with front wind or small forward movement may result in enhanced under pressures in the aft part of the aircraft causing a suction down force and a change of the pitching moment towards the ground.