1,720,967 research outputs found
Study on the effect of raindrops on the dynamic stall of a NACA-0012 airfoil
Full text linkIn this study the pure effect of raindrops on dynamic stall of a pitching airfoil has been investigated. The simulation was performed at Reynolds number of 106 with raindrop diameter equal to 10−5m. A couple of multiphase models based on Eulerian and Lagrangian frames of reference have been implemented to simulate the raindrops. In the first step the accuracy of each multiphase model has been appraised. As a result, the Lagrangian multiphase model, which is called Discrete Phase Model, has been proven to be of better accuracy. It has been concluded that in general raindrops has negative effects on the lift coefficient of the pitching airfoil. In addition, a lead in aerodynamic phenomena has been observed due to the presence of water drops. This phenomenon has also been observed in the formation and separation of Leading Edge and Trailing Edge vortices which come to existence in advance of the dry case. Finally, it has been illustrated that the main effect of raindrops is on the phase of force oscillation rather than the force amplitude
Assessment of URANS and LES Methods in Predicting Wake Shed Behind a Vertical Axis Wind Turbine
Full text linkIn order to shed light on the Vertical-Axis Wind Turbines (VAWT) wake
characteristics, in this paper we present high-fidelity CFD simulations of the
flow around an exemplary H-shaped VAWT turbine, and we propose to apply Proper
Orthogonal Decomposition (POD) to the computed flow field in the near wake of
the rotor. The turbine under consideration was widely studied in previous
experimental and computational investigations. In the first part of the study,
multiple Reynolds-Averaged Navier-Stokes (RANS) simulations were performed at
the Tip Speed Ratio (TSR) of peak power coefficient, to select the most
accurate turbulence model with respect to available data. In the following
step, further RANS numerical simulations were performed at different TSRs to
compare the power coefficient against experimental data. Then, Large Eddy
Simulation (LES) was applied for multiple TSR conditions. The spatial and
temporal POD modes along with modal energy for the RANS and LES results were
extracted, and the performance of the turbulence models was assessed. Also, an
interpretation of the POD modes with respect to the flow structures was given
to highlight the most significant time and length scales of the predictions
considering the different dynamical levels of approximations of the
computational models.Comment: 15 Page
Effect of particle aspect ratio in targeted drug delivery in abdominal aortic aneurysm
No full textAneurysm is a permanent irreversible bulge in the artery that can occur with higher prevalence among elderly individuals. Although invasive surgical procedures can prevent their development, they come with considerable side effects. Recently, treatments based on targeted drug delivery have gained a lot of attention to suppress aneurysm growth. Numerical simulations have been shown to be of great role in the prediction of blood hemodynamics and vascular wall behaviour in the case of an aneurysm. Moreover, the utilization of high-fidelity approaches such as the Lagrangian frame of reference can address the motion characteristics of microbubble (MB) contrast agents in particulate flows. This study aims to investigate the effect of particle aspect ratio on the adhesion of oblate spheroid particles to the vascular wall. Accordingly, a two-way fluid–structure interaction (FSI) method consisting of a hyperelastic material model for the vessel along with a non-Newtonian, compressible model for blood was employed to simulate an abdominal aortic aneurysm (AAA). Moreover, the ligand–receptor binding concept has been utilized to address the quantification of MBs adhesion. Five sets of aspect ratios ranging from 1 to 9 have been investigated and results indicated that with the increase of the aspect ratio the rate of adhesion decreases. Two drastic changes in the particle number occurred due to the diastolic peak and negative velocity profile, respectively. However, it was concluded that the hydrodynamic of the MBs in terms of velocity and wall distance is rather insensible to the particle shape.</p
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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