1,720,961 research outputs found
Control of Transonic Shock Wave Oscillation over a Supercritical Airfoil
No full textIn the present study, a numerical investigation is carried out on the aerodynamic performance of a
supercritical airfoil RAE 2822. Transonic flow fields are considered where self-excited shock wave
oscillation prevails. To control the shock oscillation, a passive technique in the form of an open
rectangular cavity is introduced on the upper surface of the airfoil where the shock wave oscillates.
Reynolds Averaged Navier-Stokes (RANS) equations have been used to predict the aerodynamic
behavior of the baseline airfoil and airfoil with cavity at Mach number of 0.729 and at angle of attack
of 5˚. The aerodynamic characteristics of the baseline airfoil are well validated with the
available experimental data. It is observed that the introduction of a cavity around the airfoil upper
surface can completely stop the self-excited shock wave oscillation and successively improve
the aerodynamic characteristics
Control of Transonic Shock Wave Oscillation over a Supercritical Airfoil
No full textIn the present study, a numerical investigation is carried out on the aerodynamic performance of a
supercritical airfoil RAE 2822. Transonic flow fields are considered where self-excited shock wave
oscillation prevails. To control the shock oscillation, a passive technique in the form of an open
rectangular cavity is introduced on the upper surface of the airfoil where the shock wave oscillates.
Reynolds Averaged Navier-Stokes (RANS) equations have been used to predict the aerodynamic
behavior of the baseline airfoil and airfoil with cavity at Mach number of 0.729 and at angle of attack
of 5˚. The aerodynamic characteristics of the baseline airfoil are well validated with the
available experimental data. It is observed that the introduction of a cavity around the airfoil upper
surface can completely stop the self-excited shock wave oscillation and successively improve
the aerodynamic characteristics
Dynamics of thin films through molecular simulations
No full textThin liquid films play pivotal roles in various natural phenomena and engineering processes. Yet, our understanding is limited by the scarcity of atomic insights. This work investigates the nanoscopic details of thin films and their rupture, and the transport of surfactants along the film surfaces. At this scale, experimental investigations are prohibitive; and conventional theoretical approaches are inadequate due to their reductive approximations. Therefore, this work employs molecular dynamics simulations which enables the examination at the most fundamental scale.
Present investigations of film interfaces through stress-cluster analysis reveals that higher temperature results in a more disconnected surface stress-field, contributing to an overall decrease in surface tension. Local variation of surface tension is responsible for Marangoni convection leading to rupture. The processes by which these rupture sites emerge - traditionally categorized as spinodal and heterogeneous rupture - are found to share similar molecular origin. Present study on the growth of rupture sites identified the limitations of continuum scale theories in explaining retraction rates for thinner films, and corrections are proposed that rectify the discrepancies. Notably, a spatio-temporal memory of rupture is identified, highlighting the concept of deterministic outcomes emerging from stochastic processes.
Finally, the transport mechanism of surfactant molecules, along the deforming surfaces of thin films and droplets, is investigated. The continuum scale transport equation is solved by employing a finite difference scheme, incorporating inputs from MD simulations. This model provides confirmation of the validity of the transport equation at the nanoscale. By uniquely confirming the applicability of the transport equation for a molecularly thin film, this study elucidates the long-debated relationship between the continuum and the nanoscale. Together, the findings from this research represent an important step in bridging the physics of fluids across scales, offering new insights to the dynamics of thin films.Open Acces
Dynamics of Compound Droplets: Rolling and Evaporation
Full text linkSuperior control of multiphase micro-drops owns much of the future in microfluidic technology. Understanding the dynamics of such compound systems is the key to its large-scale applications. Interfacial interaction of a droplet at a liquid-fluid interface dictates its successful generation and stability. The knowledge of the interface dynamics creates a rich profusion of domains that were previously unexplored. The century-old power law, which was believed to be universal in governing temporal drop spreading on solid substrates, is seen to fail in predicting spreading on liquid-fluid interface. Rather a coalescence like behavior becomes imminent. The study of the fundamental physics of evaporation of double emulsion droplets and under liquid rolling dynamics are extensions of the successful generation technique. In contrast to the rigid body motion, dissipation inside and outside of a deformable drop always results in convoluted physics. While rolling on an incline, single-phase drops travel slower with increase in size. But a concealed direct dependency between the drop size and traveling velocity can be exposed by merely altering the medium resistance. Rolling motion of double emulsion droplets even affirms the presence of both of these dependencies and a control over the transition from one to the other is achievable. A threshold size limit for such a transition has been identified demonstrating that the dependency between drop size and its velocity is not unidirectional. This thesis further explores the evaporation of double emulsion droplets and identifies two new regimes of evaporation. Resurfacing of a daughter droplet from an evanescing drop preceded by sudden spreading are uncommon observations in the literature. Detailed comprehension of the resurfacing of micro-droplets provides a possibility to control the evaporation mode, which was considered to be a random occurrence in the past
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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