1,720,961 research outputs found
Analysis of effects of the free surface on the movement of a tethered sphere immersed in a steady flow
No full textIn this work, we study the effects of the free surface on the sphere immersed in a steady flow through the analysis of stream wise and transverse displacements. The range of relative submergence, h*, is between 0 and 0.75 and the tethered sphere is characterized by a low value of the mass ratio m*~1 and a low value of damping ratio (ζ=0.007). The movements of the sphere have been measured using two methods: (a) by means of an analogue laser displacement sensor, and (b) by image analysis of the sphere movement CCD acquisitions. The second method provided the 2D reconstruction of the trajectory. The experimental data have highlighted a significant influence of free surface flow both on the transverse oscillation amplitudes and on the oscillation frequencies of the sphere
Estimation of Hydrodynamic Loading on an Oscillating Sphere
No full textThe design of flexible submerged structures presents issues related to e.g. hydrodynamics loads, induced hydrodynamic motion, effect due to the vortex-induced vibrations, re-sonance phenomena. In this complex scenario results form simple benchmark studies are valuable.
Recently, the motion, due to hydrodynamic loading, of an oscillating sphere characterized by low values of mass and damping has been studied by the authors in an free surface flow channel at different values of relative submersion. Knowledge of the mechanical response and of the principal dynamic characteristics of the sphere retaining (mooring) system allows for the reconstruction of the hydrodynamic loading starting form measured displacements.
This paper reports on the experimental work carried out to characterize the retaining system and the consequences coming from the estimated structural parameters on non-dimensional hydrodynamic force coefficients
Boundaries effects on the movements of a sphere immersed in a free surface flow
No full textThis work analyses the influence of boundary conditions on the movements of a sphere immersed in a steady free surface flow. The sphere is free to move in both transverse and stream wise directions and it is characterized by values of the mass ratio, m*, equal to 1.34 and of the damping ratio, ζ, equal to 0.006. In all the experiments the blockage coefficient is kept constant, while the sphere is located at different distances from the free surface and from the bottom wall of the channel. The movements of the sphere have been measured by means of the image analysis of CCD camera which provides the 2D (stream wise and transverse) displacements of the sphere with a temporal resolution of 0.02. The experimental data show a significant influence of the boundaries on the sphere movement and highlight a different behaviour of the amplitude response between the three different experimental set-ups considered
Dynamic Response of a Sphere Immersed in a Shallow Water Flow
No full textThis work analyses the dynamic response of a sphere located close to the floor of an hydraulic channel within steady free-surface current flows. The sphere is free to move in transverse (y) and streamwise (x) directions and it is characterized by a mass ratio, m*, equal to 1.34. The oscillation amplitudes and the frequencies of the sphere have been measured by means of the image analysis of a Charge Coupled Device (CCD) camera. The experimental data show a significant influence of the free surface on the sphere movement and highlight a different behaviour of the dynamic response to the increasing of the water level on the upper part of the body
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
- …
