1,721,014 research outputs found
Wave-field flow structures developing around largediameter vertical circular cylinder
No full textIn this work the issue of wave-induced flow structures that develop around a large-diameter surface-piercing vertical circular cylinder is addressed. A strictly-linear wave case is considered and simulated numerically, solving the Euler equations in primitive variables, and the results are compared with those obtained from the corresponding close-form velocity-potential solution. Then, the swirling-strength criterion for flow-structure eduction is applied to the primitive-variable Euler-equations-derived velocity field. It is found that differently-shaped flow structures develop at the free surface and under the free surface, in particular at the cylinder wall. This field of structures is not detectable from the potential-derived velocity field, due to the purely mathematical nature of the latter
On evaluation of wave forces and runups on cylindrical obstacles
No full textA computational analysis of diffraction of water waves caused by large-diameter circular cylinder piercing the free surface is performed. With reference to linear-wave cases, the phenomenon is considered in terms of: i) velocity-potential theory, ii) numerical solution of the primitive-variable Euler equations, and iii) numerical solution of the primitive-variable full Navier–Stokes equations. It is found that, as for the values of the forces exerted by the wave on the cylinder, the results obtained from the numerical integration of the Euler equations and from the potential theory slightly underestimate those obtained from the numerical integration of the Navier–Stokes equations (and also from experimental results obtained by other authors), while both the potential theory and Euler equations results strongly underestimate the values of the runups on the cylinder as compared with the Navier–Stokes equations results (and also with the experimental results obtained by other authors). Thus, new concise expressions for evaluating both forces and runups are proposed
WAVE-FIELD FLOW STRUCTURES DEVELOPING AROUND LARGE-DIAMETER VERTICAL CIRCULAR CYLINDER
No full textIn this work the issue of wave-induced flow structures that develop around a large-diameter surface-piercing vertical circular cylinder is addressed. A strictly-linear wave case is considered and simulated numerically, solving the Euler equations in primitive variables, and the results are compared with those obtained from the corresponding close-form velocity-potential solution. Then, the swirling-strength criterion for flow-structure eduction is applied to the primitive-variable Euler-equations-derived velocity field. It is found that differently-shaped flow structures develop at the free surface and under the free surface, in particular at the cylinder wall. This field of structures is not detectable from the potential-derived velocity field, due to the purely mathematical nature of the latter
The Field of Flow Structures Generated by a Wave of Viscous Fluid Around Vertical Circular Cylinder Piercing the Free Surface
Full text linkAbstractThe diffraction of water waves induced by a large-diameter, surface-piercing, vertical circular cylinder is studied numerically. The Navier-Stokes equations in primitive variables are considered for the simulation of a given wave case, and the technique is followed of the Direct Numerical Simulation (DNS). The criterion of the imaginary part of the complex-eigenvalue pair of the velocity-gradient tensor for the extraction of the flow vortical structures is applied to the computed fields, so unveiling a complex configuration of structures at the free surface, and at the cylinder external walls. The most energetic modes of the flow are further extracted from the DNS-simulated fields by using the Karhunen-Loève decomposition (KL). A “reduced” velocity field is reconstructed using the first three most energetic eigenfunctions of the decomposition, and its evolution is followed through a sequence of time steps
Simplified model for an alpha2-omega dynamo fed by dynamical evolution of the zonal shear
No full textStructures of a viscous-wave flow around a large-diameter circular cylinder
No full textAn analysis of the phenomenon of diffraction of viscous (water) waves caused by a large-diameter, surface-piercing vertical circular cylinder is performed. The three-dimensional time-dependent Navier-Stokes equations in primitive variables (velocity-pressure formulation) are considered for numerical simulation of the given wave case, and (for the first time at the best of the authors' knowledge) an approach followed is that of the Direct Numerical Simulation (DNS), with no models being used in the calculations for the fluctuating portion of the velocity field. The results obtained in terms of the wave runup and in-line force are compared with those given by the close-form velocity-potential solution for the same wave case and, with those given by the numerical integration of the primitive-variable Euler equations, as well as with data of experimental nature obtained by other authors. For further investigation of the flow fields, the swirling-strength criterion for flow-structure extraction is applied to the computed velocity fields, so unveiling a complex configuration of the viscous-flow structures in the vicinity of the cylinder external wall
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
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