1,720,965 research outputs found
Finite Volume Compact Schemes on Staggered Grids
No full textCompact finite-difference schemes have been recently used in several Direct Numerical Simulations of turbulent
flows, since they can achieve high-order accuracy and high resolution without exceedingly increasing the size of the
computational stencil. The development of compact finite-volume schemes is more involved, due to the appearance of
surface and volume integrals. While Pereira et al. [J. Comput. Phys. 167 (2001)] and Smirnov et al. [AIAA Paper, 2546,
2001] focused on collocated grids, in this paper we use the staggered grid arrangement. Compact schemes can be tuned
to achieve very high resolution for a given formal order of accuracy. We develop and test high-resolution schemes by
following a procedure proposed by Lele [J. Comput. Phys. 103 (1992)] which, to the best of our knowledge, has not yet
been applied to compact finite-volume methods on staggered grids. Results from several one- and two-dimensional
simulations for the scalar transport and Navier–Stokes equations are presented, showing that the proposed method is
capable to accurately reproduce complex steady and unsteady flows
A Phase-Field Approach for Liquid-Liquid Flow Simulations
No full textA phase-field approach is presented for the numerical simulation of two-phase forced flow in channels. The difference in physical properties of the two components is handled following a quasi-incompressible approach (Lowengrub and Truskinovsky [16]). The axisymmetric form of the Navier − Stokes and Cahn − Hilliard equations system is solved for a narrow pipe of radius R = 1 mm, where buoyancy effects are neglected. Results of three simulations for the evolution of spherical and elongated bubbles are reported
Experimental investigation of three phase oil/water/air flow
No full textThree-phase flow of oil, water and air is investigated in a horizontal pipe of inner diameter 40 mm. The mineral oil used in the experiments is similar to crude oil transported in industrial pipelines with a viscosity of μo = 0.919 Pa s and ro = 889 kg/m3 at 20◦C. Careful measurements of pressure drop are performed at different flow rates of the liquids and with the air superficial velocity being varied in steps between Jg = 0.0 m/s and Jg ≈ 6.5 m/s. The pressure drop behaviour depends upon the initial two-phase flow regime of the two liquids, and in most cases it shows a progressive increase caused by the injection of air. A wide variety of flow patterns is observed: pictures of flow configurations obtained by starting with the two liquids in core-annular and wavy-annular regimes are provided together with full descriptions
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
Experimental analysis of flow regimes and pressure drop reduction in oil–water mixtures
No full textThe physical understanding of two-phase flow characteristics in horizontal pipes is of importance in the petroleum industry since significant savings in pumping power can be derived from the water-lubricated transportation of crude oil.An experimental study of water continuous oil–water flow in horizontal pipes is performed using mineral oil and tap water of viscosity ratio about 900 and density ratio 0.9. A set of seven different pipes of Pyrex and Plexiglas where used, with diameters ranging between 21 and 40 mm. Pressure drop measurements, flow pattern maps and clear pictures of the oil–water flow are reported in this article together with comprehensive comments. The results obtained are compared to empirical laws, theoretical findings and experimental results by different authors in the literature.In order to identify the regions with operational conditions that are suitable for applications, a novel criterion for the location of the annular/stratified transition is proposed which is based only on experimental observations
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
From two phsae oil water to three phase oil/water/air flows in horizontal pipes: pressure drop and flow regimes.
No full textThe interest in oil-water pipe flow descends from its importance in petrochemical industries; pumping power requirements during oil transportation is considerably reduced in the core-annular flow regime. In petroleum transportation pipelines, an additional phase of natural gas frequently flows with the oil. The prediction of pressure drop and stability characteristics of the three-phase flow in these lines is important for proper operation of the transportation plants at reduced power consumption. Results from a set of experiments of three-phase flow of high viscosity oil, water and air in horizontal pipes of two different diameters are presented in the paper. Pressure drop measurements are related to three phase flow patterns observations in a defined range of specific flow rates of water, oil and air. When air is supplied in a wavy-stratified flow of oil and water, the presence of air plugs hinders stratification and ensures a lower resistance as respect the corresponding oil-water case; disturbances induced by the gaseous phase grow rapidly with increasing air specific flow rate and the tendency is reversed by a higer flow rate of air. The presence of air in an annular flow of oil induce large quasi-periodic deformations of the interface between oil and water and has a negative effect on drag
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