1,720,997 research outputs found
A novel high-fidelity two-way coupling model for fluid-structure interaction in wind energy
No full textTo increase the attractiveness of wind energy, wind turbines are continuously scaling up, with diameters now exceeding 200 m. If on the one hand, this trend guarantees an increased power production, on the other hand, it imposes harsher aerodynamical and structural requirements – on the blades in particular – that are difficult to characterise. In particular, the significant size of the state-of-the-art wind turbines suggests a more relevant Fluid-Structure Interaction (FSI) that could alter dramatically the operating life of the full machine. Given the difficulties and the costs of measuring the phenomena occurring at significant scales, researchers advocate the development of high-fidelity numerical models exploiting Computational Fluid and Structural Dynamics (CFD-CSD models). For this reason, in this work we present a novel FSI model for wind turbines combining our Large Eddy Simulation (LES) fluid solver with a modal beam-like structural solver. In the first part of the work, we present the details of our FSI methodology, and we analyse the effects of different coupling conditions. A loose algorithm couples the Actuator Line Model (ALM), which represents the blades in the fluid domain by means of body forces, with the structural model, which represents the flexural and torsional deformations. For a reference utility-scale wind turbine, we compare the results of three sets of simulations. Firstly, we consider one-way coupled simulations where only the fluid solver provides the structural solver with the aerodynamic loads; then, we consider two-way coupled simulations where
the structural feedback to the fluid solver is made of the out-of-plane and in-plane bending deformation velocities only; finally, we add to the feedback also the torsional deformation.
However, to accurately reproduce the airloads, one should notice that the blades in particular are subjected to many relevant sources of unsteadiness, e.g. tower shadowing, yawed and waked conditions, environmental effects. Therefore, researchers have questioned the use of steady aerodynamics in the numerical fluid and aeroelastic models used in wind energy that do not have the sufficient resolution to solve the flow close to the blade, arguing that the use of tabulated airfoil coefficients could neglect effects that alter the estimation of the turbine behaviour. Different unsteady aerodynamics models have been proposed to account for these effects but have been mainly implemented in low-fidelity engineering models, which lack the complete capability of describing the multiscale and multi-physics phenomena characterising the wind turbine. For this reason, in the second part of the work, a 2D unsteady aerodynamics model is implemented in the sectional estimation of the airloads of the Actuator Line Model. At each section of the blade, a semi-empirical Beddoes-Leishman model includes the effects of additional noncirculatory terms, unsteady trailing edge separation and dynamic stall in the dynamic evaluation of the aerodynamic coefficients of the airfoils, used to determine the ALM body forces. Different inflow conditions and aeroelastic behaviours are examined with the aim of examining the effects of the model, and thus of providing a deeper insight into the unsteady characterisation of large wind turbines by means of a high-fidelity CFD-CSD model
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
Anisotropic dynamics and sub-grid energy transfer in wall-turbulence
No full textPurpose of the present work is the analysis of the generalized Kolmogorov equation applied to the direct numerical simulation data of a turbulent channel flow. The multi-dimensional description of the anisotropic behavior of turbulent energy production, transport, and dissipation is shown to be relevant for the understanding and modeling of the wall-turbulent physics with special care to the phenomenon of reverse energy flux. These results are proven instrumental also for the correct computation of wall-turbulence when a large eddy simulation approach is considered. The capability of a filtered velocity field to correctly reproduce the wall-turbulent dynamics at different ranges of scales and wall-distances as a function of the filter length will be assessed via filtered direct numerical simulation (DNS) and large eddy simulation data. The possibility of new modeling approaches is also highlighted
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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