1,720,974 research outputs found
Methodology for the design and optimization of a morphing wing droop-nose structure for greener aircraft
No full textDroop-Nose Leading Edge (DNLE) morphing wings are one of the most promising devices in order to achieve aerodynamic drag and noise reduction during take-off and landing phases. An accurate design of these structures could lead to the decrease of aircraft fuel consumption in the perspective of reaching a greener aviation, following the objectives indicated by Flightpath 2050 issued by the E.U. However, due to the challenges related to the realization of this technology and TRL reached, DNLE are more likely implemented in Unmanned Aerial Systems (UAS) for testing and evaluation purposes. In the present study, an optimization methodology for the DNLE composite laminate skin and morphing mechanism structure is proposed and applied to a study case represented by the UAS-S45 aircraft. The work starts from the morphing leading edge structure developed by the LARCASE laboratory at ETS Montreal. The results showed that by means of the optimization strategy adopted, the force required on the actuator mechanism is 88% lower than the original design. A significant improvement on the profile smoothness along its section and in the spanwise direction in morphing conditions has been obtained too. However, further investigations are still needed in order to achieve a more appropriate morphing shape. Despite this, it appears from the results obtained that the proposed methodology can be useful to tackle the DNLE design problem in an effective and efficient way. What developed in this work has been conceived to support the investigation of DNLE in the small leading edge profiles typical of the UAS. In this way, an easier procedure for the set up of the design flow, and a decrease in the computational effort for the optimization process can be obtained. An experimental validation of the results obtained is currently being performed at ETS, and future development regards the assessment of the errors of the numeric procedure herein presented respect to real data
Aerodynamic design optimization and flow separation control of the UAS-S45 using wing morphing technology
Get PDFModern aircraft design is greatly impacted by environmental considerations, such as noise and carbon emissions, fuel efficiency improvement, and carbon-neutral growth, and the rise of fuel prices has also made fuel efficiency a vital element in aircraft design. The aviation sector has used many strategies to meet these goals, and this thesis aims to develop a morphing wing concept based on the Morphing Leading Edge (MLE) and Morphing Trailing Edge (MTE) to increase the aerodynamic efficiency of an aircraft. Therefore, an aerodynamic and structural optimization for the UAS-S45 airfoil using morphing wing technology was performed at the Research Laboratory in Active Controls, Avionics, and AeroServoElasticity (LARCASE).
This includes an optimization framework, which combines an optimization algorithm, airfoil parameterization techniques, and an aerodynamic solver. To obtain the optimized wing shapes, different parameterization methods, such as the Bezier-Parsec (BP), Class Shape Transformation (CST), and Makima methods, and optimization algorithms, such as the Coupled Particle Swarm Optimization (PSO)-Pattern search (PS), Genetic Algorithm, and Black Window Optimization (BWO) were implemented. The effects of various parameterization techniques and algorithm choices on computing time and the results of aerodynamic optimization are investigated. Several objective functions, such as drag minimization, lift-to-drag maximization, and maximizing aerodynamic endurance performance, were used to optimize the airfoil shapes. An aerodynamic solver was coupled with an in-house MATLAB-based optimization framework. The parameterization methods were integrated with the two-dimensional aerodynamic solver known as XFoil, and the Transition (y - Reꝋ) turbulence model was used to validate the results.
The optimization results revealed that Morphing Leading Edge (MLE) and Morphing Trailing Edge (MTE) wings improve their aerodynamic performance at different flight conditions. Such as, the lift coefficient of the MLE airfoil was increased by 21%, and the maximum lift coefficient was increased to 9.6%. In addition, a 3-degree delay for the stall angle of attack was observed. The MTE configurations also showed a significant improvement in aerodynamic performance. The MTE airfoils increased the maximum lift coefficient to 8.13%, and the endurance was maximized by increasing CL3/2/CD by 10.25%. Overall, the morphing wing potentially increased the maximum lift coefficient, delayed the separation of the boundary layer, and increased the stall angle of attack.
In addition, a preliminary structural optimization was conducted to assist in the design and analysis of a morphing leading-edge structure using the parametric sensitivity analysis. The correlation among the design variables, such as composite laminate thickness, material properties, ply orientation, number of plies, etc., and the parameters for two failure criteria, maximum stress failure, and Tsai-Wu failure, were evaluated. The investigation helped in obtaining the important variables which are significant for the morphing wing design. The correlation and determination matrices along with scatter plots were obtained for all the design parameters, and therefore, these results were used to design the composite morphing leading-edge wing.
Furthermore, the use of morphing wing technology as a stall control technique was studied because dynamic stall control occurs in all aerospace applications. The need for dynamic stall control is crucial for UAVs and military aircraft, as they require a high level of maneuverability. The design and implementation of the Dynamically Morphing Leading Edge (DMLE) technology were comprehensively investigated for different morphing parameters, such as deflection frequency and amplitude, and the morphing starting time. It was effective in controlling the formation and development of leading-edge vortex and flows separation, thus preventing the airfoil from experiencing dynamic stall
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Investigation on the prominence of abrupt expansion on the base pressure of an axi-symmetric body
No full textThis investigation presents the outcome of the tests conducted to control the base flows at supersonic Mach numbers. Also the efficiency of the flow controllers to govern the pressure in the base region in a rapidly expanded duct has been exercised. Four tiny jets of 1mm diameter are positioned at 90 intervals at a distance of 6.5 mm from the central axis of the main jet. The inertia levels of the abruptly expanded flows are 1.25, 1.3, 1.48, 1.6, 1.8, 2.0, 2.5 and 3.0. These jets are connected by an axi-symmetric circular brass tube whose cross-sectional area was 2.56, 3.24, 4.84 and 6.25 respectively. The L/D ratio of the enlarged duct was varied from 10 to 1 and NPR was varied from 3 to 11. However, the results presented were for Low Length to Diameter ratio, equal to 4. It was found that when the flow was discharged to the ducts of the given area ratios, it remained attached with the duct wall for all the inertia levels and the NPRs tested in the present case. It was found that the expansion level plays a significant role to decide the pressure at the base and its control efficacy. Whenever, the flow is over expanded, an oblique shock is formed at the nozzle lip, which in turn leads to enhancement of the pressure in the base region. The formation of the shock waves, reflection and recombination continued till the pressure becomes atmospheric. It was observed that the flow remains attached even for low length-to-diameter ratio, equal to 4. No adverse effect of back pressure was observed during the test. It was found that the micro jets can serve as controllers for the base pressure
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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