1,721,007 research outputs found
Hybrid RANS/LES simulations of a bluff-body flow
No full textA hybrid RANS/LES approach, based on the Limited Numerical Scales concept, is applied to the numerical simulation of the flow around a square cylinder. The key feature of this approach is a blending between two eddy-viscosities, one given by the k - ε RANS model and the other by the Smagorinsky LES closure. A mixed finite-element/finite-volume formulation is used for the numerical discretization on unstructured grids. The results obtained with the hybrid approach are compared with those given by RANS and LES simulations for three different grid resolutions; comparisons with experimental data and numerical results in the literature are also provided. It is shown that, if the grid resolution is adequate for LES, the hybrid model recovers the LES accuracy. For coarser grid resolutions, the blending criterion appears to be effective to improve the accuracy of the results with respect to both LES and RANS simulations
An Hybrid RANS/LES Approach Applied to Bluff-Body Flow Simulation
No full textA recently developed hybrid RANS/LES model, known as the Limited Nu- merical Scale approach (LNS), is applied to the simulation of the flow around a square cylinder at a Reynolds number, based on the free-stream velocity and on the side length, equal to Re = 2.2 · 104. The hybrid model uses an eddy-viscosity which is given by a local blending, depending on the grid resolution, between two eddy viscosities coming re- spectively from the k − ε RANS closure and from the Smagorinsky LES model. A mixed finite-element/finite-volume formulation on unstructured grids is used to discretize the LNS equations. The results obtained with the hybrid approach are compared with those given by RANS and LES simulations for two different grid resolutions; comparisons with experimental data and numerical results in the literature are also provided. It is shown that, when the resolution is adequate for LES, the LES accuracy is recovered by the LNS model. For a coarser resolution, the blending criterion noticeably improves the results with respect to both RANS and LES approaches
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
Mixed subgrid scale models for classical and variational multiscale large-eddy simulations on unstructured grids
No full textNumerical diffusion based on high-order derivatives in MUSCL schemes for LES on unstructured grids
No full textA MUSCL scheme in which stabilization is obtained through numerical
diffusion based on sixth-order derivatives is presented.
Such a dissipation has a very localized effect on high
frequencies and, thus, the interaction with SGS modeling should be reduced.
Moreover, a key coefficient permits to tune the numerical dissipation
to the minimum amount required to obtain stable calculations.
The proposed approach is applied to the large-eddy simulation of the
flow around a square cylinder on an unstructured grid. Results are
compared with experimental and LES data in the literature and with
the results obtained in previous simulations carried out with upwinding
based on fourth-order derivatives
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