1,721,020 research outputs found
Code to Code Comparison of Aircraft-Mode Tilt-Rotor Aerodynamics
No full textA global comparison of several blind-test numerical predictions of the aerodynamic field around the
Erica model in aircraft mode, carried out by some Partners of the NICETRIP consortium, is presented.
The calculations are carried out with different codes, different turbulence models, different wind tunnel
setups and different grids, with the objective of supporting the future experimental test campaign in
the DNW-LLF and ONERA S1Ma wind tunnels. It is found that the level of unsteadiness introduced
by the rotor wake on the aerodynamic loads on the fuselage, wing and nacelle may be relevant. The
influence of the lower-mounted wind tunnel support is rather limited, while the rear-mounted support
introduces some local unsteady effects on the fuselage loads. The overall qualitative agreement of the
pressure distributions among different calculations is acceptable, while the scatter of the quantitative
average loads is somewhat important
Trimmed Actuator Disk Modeling for Helicopter Rotor
No full textThe goal of this work has been to develop a method to compute the trim commands for an helicopter rotor using an Actuator Disc (AD) model where the source distribution and the orientation of the disc with respect to the shaft axis are adapted during the simulation, in order to meet the prescribed trim state. In a standard AD simulation the momentum source is assigned a priori, being usually provided by a CFD or BEM simulation with imposed kinematics. In this work the source distribution is provided by a multibody trimmed rotor simulation. The trimmed AD model has been embedded in ROSITA [1], a compressible RANS solver developed at Politecnico di Milano. ROSITA uses a system of overset grids (Chimera), which allow to give the actuator disc grid the same orientation as the rotor tip path plane without the need of remeshing. Thanks to this particular feature, both propulsive and moment trim can be performed. The source terms on the disc are obtained from a loose coupling between a CSD code (MBDyn [2]) and ROSITA. In particular when MBDyn has reached a periodic trimmed state, it provides a rotor map (a radial and azimuthal force distribution) and the disc orientation to the CFD solver. ROSITA is then run till a steady inflow condition is reached at the disc surface, thus providing an updated inflow map to the CSD solver. By iterating this procedure it is possible to reach the convergence at the desired rotor state. The coupling method has demonstrated to have a good convergence rate, in fact the solution becomes stable after about 5-10 cycles. As it can be seen in figures 1 and 2, both the shape of the pressure distribution on the rotor disc and the Fourier components of the hinge angles have reached a converged state. Results achieved with this simplified rotor model compare positively with both experimental results (fig. 3) and trimmed numerical simulations of the full rotor, thus representing a good compromise between the quality of results and the computational effort
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
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