1,720,961 research outputs found
PREDICTION OF TURBULENT OFFSET JET FLOWS WITH AN ASSESSMENT OF QUICKER SCHEME
No full textThe QUICKER scheme extended for non-uniform rectangular grid systems has been applied to predict the turbulent offset jet flows. Computational results obtained with the QUICKER scheme are compared with those from the skew-upwind and the hybrid schemes. Computational results include the reattachment length, the velocity profile, the axial velocity decay curve, and the shear stress distribution. In the sense of an overall agreement with the experimental data, the QUICKER scheme is found to be superior to the other two schemes. Boundary conditions are carefully set up to account for various flow conditions. Special attention has been given to the set-up of entrainment boundary condition. It is emphasized that the numerical diffusion due to streamline-to-grid skewness far exceeds the turbulent diffusion in offset jet flows; therefore, a numerical scheme that would minimize the numerical diffusion is a prerequisite for a better prediction of the turbulent offset jet flows
EXTENSION AND APPLICATION OF THE QUICKER SCHEME TO A NONUNIFORM RECTANGULAR GRID SYSTEM
No full textThe QUICKER formulation of the QUICK scheme is extended to a non-uniform rectangular grid system that can be widely adopted for the calculation of the flow problems of engineering interest. This new formulation is applied to obtain solutions of a one-dimensional non-linear Burgers equation and a two-dimensional lid-driven cavity flow. The computational results show that the new formulation is superior to existing schemes such as hybrid and skew-upwind-differencing, especially when the grid Peclet (or Reynolds) number is high
Convergence characteristics of temperature in radiation problems
No full textNumerical convergence of temperature in radiation problems with absorbing, emitting,and nonscattering media is examined. Iteration processes for the solution of blackbody intensity (or temperature) when using the pointwise or the control-volume energy equation are scrutinized and a sufficient condition for convergence is presented. An explicit and a few implicit methods for prescribed heat source distribution in one-, two-, and three-dimensional enclosures are devised. They are incorporated and tested with the discrete ordinates method, the discrete ordinates interpolation method [1], and the zone method, and comparison of the number of iterations for convergence as well as the solution accuracy is made. The implicit methods significantly reduce the number of iterations, and this is prominent for optically thick cases. However, they reduce the number of iterations marginally as the number of control volumes increases. A fully implicit scheme reduces the number of iterations more effectively than a semi-implicit one does. Also, taking finer (and thus more) control volumes increases the number of explicit iterations asymptotically, reaching all upper bound as a function of the total optical thickness and the convergence criterion
Comparison of three discrete ordinates methods applied to two-dimensional curved geometries
No full textThis paper describes the application and comparison of three Discrete Ordinates Methods: the Discrete Ordinates Interpolation Method (DOIM) for structured and unstructured grids; the Discrete Ordinates Method in Orthogonal Curvilinear Coordinates (DOM-OCC) for structured grid; and the Discrete Ordinates Method associated to the Finite Volume method and Ray Tracing (DOM-FV-RT) for unstructured grid. A summary of the basic equations and numerical formulations is given for each method to outline their key characteristics. In order to extract valuable information to improve DO kind methods when applied to complex geometries, they are compared in the case of radiative equilibrium of a gray medium confined between infinite black or diffusely reflecting circular or elliptical cylinders. For the circular ring problem, the three DOMs results are confronted with Monte Carlo ones for various radius ratios and radiative properties. The elliptical ring problem extends the comparison to a more complex geometry and an emphasis is put on the evaluation of wall radiation fluxes, In conclusion, distinctive features in terms of performances are observed for each method. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved
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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