1,721,017 research outputs found
Flow distortion around underwater gliders and impacts on sensor measurements: a pilot study using large-eddy simulations
No full textThe suitability of computational fluid dynamics (CFD) to numerically simulate the flow of water over autonomous underwater vehicles (AUVs) was investigated. The aim was to examine the feasibility of using large-eddy simulation to investigate; 1) the extent to which the measurements of sensors (including turbulence sensors) on an AUV are affected by the distortion of the flow around the vehicle body, and 2) the quantification of the hydrodynamic forces on AUV’s. To this end the large-eddy simulation (LES) code Gerris was used to numerically simulate the flow around underwater gliders.Two example simulations were conducted. In both cases the flow around a Slocum Mk II glider was simulated and the second example included a MicroRider turbulence package mounted on top of the glider. The results of these studies illustrate the capability of CFD simulations but a more detailed study including further runs to examine the sensitivity of the results to model parameters and in some cases validation with experimental studies would be required before we could have full confidence in the results.The results suggest that CFD studies may have significant value in assessing the flow distortion around glider bodies and the resulting affects upon sensor measurements. Our preliminary results suggest that the usual position of the oxygen sensor on a Slocum glider may be within a separated wake that could significantly affect the data quality. Flow distortion at the location of the shear probes on the turbulence package is low but could result in a small underestimation of the magnitude of dissipation. Lift and drag forces diagnosed from the simulations were consistent with data from gliders but a more detailed study is needed to assess the quantitative accuracy of these results
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
Corrigendum to “Transition in a numerical model of contact line dynamics and forced dewetting” (Journal of Computational Physics (2018) 374 (1061–1093), (S0021999118305357) (10.1016/j.jcp.2018.06.078))
No full textWe correct an error by a factor of “e” in several equations of Afkhami et al. (2018) [1]
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
An edge-based interface tracking (EBIT) method for multiphase-flow simulation with surface tension
Full text linkWe present a novel Front -Tracking method, the Edge -Based Interface Tracking (EBIT) method for multiphase flow simulations. In the EBIT method, the markers are located on the grid edges and the interface can be reconstructed without storing the connectivity of the markers. This feature makes the process of marker addition or removal easier than in the traditional Front -Tracking method. The EBIT method also allows almost automatic parallelization due to the lack of explicit connectivity. In a previous journal article we have presented the kinematic part of the EBIT method, that includes the algorithms for piecewise linear reconstruction and advection of the interface. Here, we complete the presentation of the EBIT method and combine the kinematic algorithm with a Navier-Stokes solver. A circle fit is now implemented to improve the accuracy of mass conservation in the reconstruction phase. Furthermore, to identify the reference phase and to distinguish ambiguous topological configurations, we introduce a new feature: the Color Vertex. For the coupling with the Navier-Stokes equations, we first calculate volume fractions from the position of the markers and the Color Vertex, then viscosity and density fields from the computed volume fractions and finally surface tension stresses with the Height -Function method. In addition, an automatic topology change algorithm is implemented into the EBIT method, making it possible the simulation of more complex flows. The two-dimensional version of the EBIT method has been implemented in the free Basilisk platform, and validated with seven standard test cases: stagnation flow, translation with uniform velocity, single vortex, Zalesak's disk, capillary wave, Rayleigh -Taylor instability and rising bubble. The results are compared with those obtained with the Volume -of -Fluid (VOF) method already implemented in Basilisk
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
Large eddy simulations of flow around underwater gliders and the impact on sensor measurements
No full textNumerical studies of the flow over an underwater glider was simulated to investigate; 1) the extent to which the measurements of sensors (including turbulence sensors) on an AUV are affected by the distortion of the flow around the vehicle body, 2) the occurrence of bioluminescence in the wakes of autonomous vehicles, and 3) the quantification of the hydrodynamic forces on AUV’s. Two example simulations were conducted. In both cases the flow around a Slocum Mk II glider was simulated and the second example included a MicroRider turbulence package mounted on top of the glider.
Our preliminary results suggest that the usual position of the oxygen sensor on a Slocum glider may be within a separated wake that could significantly affect the data quality. Flow distortion at the location of the shear probes on the turbulence package is low but could result in a small underestimation of the magnitude of dissipation. We also find that the shear stress on the wing edges of a glider could be sufficient to stimulate bioluminescence in certain environments but is at the lower end the range at which bioluminescence occurs. Lift and drag forces diagnosed from the simulations were consistent with data from gliders but a more detailed study is needed to assess the quantitative accuracy of these results
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
- …
