1,721,043 research outputs found
High–lift actuation weight estimation using low–cost methods
No full textCivil passenger aircraft use high-power actuation systems to deploy high–lift surfaces on the leading and trailing edges of their wings. The mass and size of these systems scales with the expected load the high–lift surfaces are deploy. The problem is that estimated maximum panel loads are not known to a high degree of confidence in the conceptual and preliminary phases of design. The consequence of this in the early phases of the design cycle is that actuation system mass cannot be incorporated to any optimisation loop and traded off against design variables as part of an aerostructural optimisation. This increases uncertainty in the wing weight and the corresponding structural design margins. Ultimately, this uncertainty degrades performance and provides pessimistic estimates of dynamic aeroelastic response. This thesis presents a solution in three parts. First it presents a method for estimating the high–lift actuation system using the aircraft’s high–lift geometry. Second, it introduces a novel approach to estimating high-lift panel loads using low cost computational methods suitable for conceptual and preliminary aircraft design. Third, it quantifies the impact of the high–lift actuation system on the dynamic aeroelastic response
Effect of mesh characteristics on the flow solutions around a multi–element airfoil using SU2
No full textThe AIAA Meshing, Visualization, and Computational Environments Technical Committee invited submissions for a special session on Mesh Effects for CFD Solutions. The goal of this special session is to quantify how changes in the mesh around a 2D multi--element aerofoil affect solution accuracy and convergence for a CFD flow solver. We used open source code SU2, with the Spalart-Allmaras turbulence model verified using the NASA turbulence modeling resource, to demonstrate the effect of varying various mesh parameters including cell type, surface spacing, and growth rate normal to the wall. Our systematic investigation allows us to contribute to the session's efforts on constituting a best practice mesh for a 2D multi-element aerofoil. In this paper we show that leading and trailing edge length for the main element is a key parameter, along with surface spacing and growth rate normal to the wall. We put bounds on their values that allow the most computational efficient approach to producing robust and accurate flow solutions using automated meshing techniques
High-lift actuation weight estimation using low-cost methods
No full textWith the relentless pressure to drive down the weight of aircraft in the pursuit of increasing fuel efficiency, accurate weight estimation is needed as early as possible in the design cycle. Multidisciplinary design optimization of wings is currently fidelity inconsistent – optimization of the load-bearing structure and aerodynamics are often performed to a high degree of precision with Reynolds-averaged Navier-Stokes solvers and finite element models for the structure. Meanwhile, estimation of non-structural weight including the high-lift system uses low fidelity correlations and rules of thumb. A preliminary estimation tool for high-lift actuation weight and sizing based on aerodynamic loads is demonstrated using two different test cases: an under-development narrow-body airliner and the NASA Common Research Model high-lift configuration
Quantifying the impact of high-lift actuator mass on dynamic aeroelasticity for the NASA Common Research Model
No full textHigh–lift actuator mass sizing and assessment of the high–speed aeroelastic properties of an aircraft are not performed concurrently in any phase of aircraft design. Failing to consider accurate estimates of actuator masses in the structural model of an aircraft may introduce certain limitations. The aim of this work was to discover the benefits of combining low–speed sizing characteristics with the performances of the clean configuration at high speeds. The high–lift configuration of the Common Research Model was used as the test case throughout. First, high–lift actuator masses at both leading and trailing edges were sized using two design philosophies that stress the importance of optimising for cost and weight. Next, a set of high–lift wing configurations were created, permuting locations of actuator masses and the values of theestimated masses. Finally, an assessment of the impact of these configurations on the flutter occurrence and on the gust load analyses were made, comparing the results to the baseline configuration. It was found that introducing high–lift actuator masses within the aeroelastic assessment is surprisingly beneficial and that conservative margins in the sizing loads can be rightly reduced, with prospective savings in structural masses
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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