1,721,035 research outputs found
Aerodynamic Constraints for Vortex Trapping Airfoils
No full textAccademia delle Scienze di Torino - Atti Sc. Fi
Secondary vortices in turbulent square duct flow
No full textA linear approach, inspired by hydrodynamic stability theory, is used to describe the presence of large scale coherent vortices for the turbulent flow in a duct of square crosssection. A set of equations for the small-amplitude coherent motion is derived and closed with a simple mixing length strategy. The initial condition that maximizes a chosen functional (related to either the kinetic energy of the coherent motion or the rate of turbulence production) is found through a direct/adjoint numerical approach borrowed from optimal control theory. It is found that different kinds of secondary flows can appear in the duct cross-section, sustained by the mean shear. Some of these optimal states display a symmetry about the bisectors and the diagonals of the duct, in agreement to experimental observations and direct numerical simulations. © 2005 by A. Bottaro, H. Soueid and B. Galletti
Low-order modelling of laminar flow regimes past a confined square cylinder
No full textA proper orthogonal decomposition based model is considered for two-dimensional vortex shedding past a confined square cylinder. The aim is to study the validity of such a model for Reynolds numbers and blockage ratios that are different from those for which the model was derived. Using a calibration procedure it is shown that reliable results can be obtained in terms of short-term (one period) dynamics. Long-term dynamics are accurately captured with a variation of the Reynolds number, whereas the error becomes large when the blockage ratio changes. The controllability and observability of vortex shedding at a slightly supercritical Reynolds number is investigated relying on the accurate low-order models obtained
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
Trapped vortices and a favourable pressure gradient
Full text linkIt is shown that there exist bodies such that in two-dimensional steady inviscid incompressible flow the pressure gradient is favourable over the entire surface of the body, and the lift is non-zero, if the body is immersed in a uniform stream and there are also two trapped point vortices.<br/
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
Clinical characteristics associated with persistent olfactory and taste alterations in COVID-19: A preliminary report on 121 patients
No full textThe role on endoscopy in alcohol-related diseases
No full textAlcohol, in addition to well-known damages on the liver and pancreas, produces direct and indirect injuries in the mucosa of the oesophagus, stomach, small intestine and large bowel. Different damages can be produced both when a large amount of alcohol is acutely drunk and when this is taken chronically. Almost all these lesions can be detected and treated by endoscopy as shown in the present article. When, over time, cirrhosis ensues the role of endoscopy is not different from that played with cirrhosis of different etiology. Beside hemorrhagic episodes, esophagitis, gastritis and cancer are the main alcohol related diseases that can be managed by endoscopy
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