1,720,967 research outputs found
Secondary Currents, Turbulence Characteristics, and Bed Shear Stress Variations in Supercritical Narrow Channel Flows
No full textSediment bypass tunnels (SBTs) belong to the active sediment management strategies of combating reservoir sedimentation, which route high-speed sediment-laden flows around reservoirs and primarily experience supercritical narrow channel flow conditions that characterize secondary currents and redistributed primary velocity, turbulence properties, and bed shear stress, which intensified by the presence of in-plan bend. These alternations in the flow characteristics influence the sediment transport, invert abrasion, and hence, the design of SBTs. Although recent laboratory-scaled experiments in straight channels produced two-dimensional flow properties, individual sediment transport, and hydro-abrasion estimate models, three-dimensional investigations are scarce, and therefore, a supplementary and cost-efficient design alternative can be the computational fluid dynamics (CFD) simulation. Furthermore, field investigations at SBT bends demonstrated deeper invert abrasion near the inner wall than toward the outer wall. However, a detailed investigation of such flow characteristics and sediment transport was missing. Under these circumstances, research was initiated at NTNU to bridge the gap between experimental and numerical studies of high-speed flows while emphasizing some of the challenges and phenomena associated with SBT hydraulics.
This research focuses on (a) developing open-source CFD models to simulate the turbulence-driven secondary currents and their interactions with the flow characteristics in straight narrow channels conveying supercritical flows and subsequently applying this model to investigate the effect of cross-sectional geometries found at SBTs and to compare open channel flows with pressurized flows or duct flows, which are sometimes observed at SBTs and (b) experimental investigation of the effect of a channel bend on the flow properties, bed shear stress, and bed load transport those are linked to the abrasion patterns observed at SBT bends and producing experimental data useful in further development of numerical models. Here, computationally economical Reynolds stress models were utilized to compute steady-state results of high-speed flows after modifying the existing model codes in OpenFOAM, as the alternate transient options are still computationally very demanding. Furthermore, a state-of-the-art particle tracking velocimetry system in conjunction with the Shake-The-Box particle tracking algorithm was employed to measure the flow characteristics in a channel bend model of the Solis SBT, Switzerland, and high-speed cameras were utilized to observe the bed load movements.
The modified Reynolds stress models compute promising results of turbulence-driven secondary currents, distributions of longitudinal velocity and turbulence parameters, and bed shear stress undulation and its averaged value for uniform supercritical flows. Channel aspect ratio influences the secondary current formations and their influence on the flow characteristics and bed shear stress. Intermediate vortex develops with decreasing aspect ratio and is fully developed for aspect ratios ≤ 1.05. The bottom vortex guides the near-bed redistribution of flow properties and bed shear stress undulation. Additionally, altering the sidewall curvature influences the bottom vortex and developing intermediate vortex, bottom corner zone of low-momentum fluids, and bed shear stress distribution. A horseshoe cross-section with plane invert is the suitable design choice over the archway and circular geometries, as it helps in shrinking the corner zone of low-momentum fluids while providing a wider invert than a circular cross-section without imposing a stress concentration. Besides, the flow properties in the bottom half flow depth and bed shear stress distribution of open channel flows are comparable to that of duct flows with the same aspect ratios, particularly for a square cross-section due to similar bottom corner configurations and comparable secondary currents. However, duct flows experience greater boundary shear stress than open channel flows. In addition, the experimental investigation indicates that the free surface undulates significantly across and along a channel bend caused by the cross-waves, the curvature-induced secondary currents and their impacts develop over a stretch in the bend, and the bed load movements in the channel bend is not a function of the bed shear stress magnitude but rather of the curvature-induced secondary currents which push and keep the sediments near the inner wall. As a result, deeper invert abrasions are formed toward that wall at SBT bends and further downstream.
This study contributes to the available knowledge of three-dimensional narrow channel flows and the interactions between hydraulic and hydrodynamic phenomena associated with high-speed sediment-laden flows, particularly for aspect ratios ≤ 2. The produced open-source CFD models are useful in computing complex three-dimensional supercritical flow characteristics in uniform narrow channels. In addition, the obtained experimental findings enlighten the hydrodynamics behind the abrasion patterns observed at SBT bends and generate data useful in validating numerical models in the future. Further advancements in computational resources in the years ahead are expected to make the alternate and more accurate transient CFD techniques feasible for supercritical flows in straight and curved channels
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
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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