1,720,993 research outputs found
Caisson Foundations for Competitive Offshore wind Farms in ITALY
No full textAbstractThe research presented in the paper moves from the results of a feasibility study recently carried out for the development of an offshore wind farm off the cost of Rimini, in the Northern Adriatic Sea. The work, based on in-situ measurements of the environmental conditions, assessed the suitability of the considered area for the development of a relatively large wind farm, although at the profitability limit. The study has considered 60 offshore wind turbines installed on monopiles, as they are, at present, the most common solution and a quantification of the investment costs could be reliably completed. With reference to such case, the paper addresses the use of caisson foundations, a convenient alternative to monopiles in water of shallow to intermediate depth, with the final aim of improving the overall cost-effectiveness of the investment
3D-numerical analysis of wave-floating structure interaction with OpenFOAM
No full textModelling of floating structures is a challenging task for offshore and coastal engineering purposes. Their design requires detailed knowledge in forces, flow velocities, rotations, displacements and loads. Highresolution numerical modelling allows for the study of their behavior under sea forcings, giving necessary information on the turbulent multiphase processes and induced loads. OpenFOAM is one of the code that offers a possibility to include Computational Fluid Dynamics approach into the design processing. In the present study, a floating vertical cylinder was chosen to evaluate the code capability to simulate moving bodies under waves. Tests reproducing the free decay were performed. Then, the wave generation tool, IHFOAM, was included to analyze the dynamics of a cylinder, moored to the bottom, under regular waves. This innovative application with OpenFOAM® represents the first step to develop a numerical wave tank where to study wave-structure interaction
Dynamic overset rans simulation of a wave-driven device for the oxygenation of deep layers
No full textThe most common methods of counteracting hypoxic events at the bottom sea layers are indirect measures aimed to reduce organic load introduced in the environment. No direct approach has been investigated except the WEBAP and OXYFLUX devices. The estimation of the surface water pumped from such devices is still largely based on physical or empirical methods. The present work adopts the CFD approach to the estimation of the pumped surface water as well as the analysis of the dynamic response of the OXYFLUX device. By means of a Reynolds-averaged Navier-Stokes code, through overset grid method, the 1:16 OXYFLUX model's dynamic response and pumping performance are evaluated under the action of 13 regular wave states. A grid sensitivity analysis is performed in order to define the best configuration able to describe the function of the device. The model is validated by comparing numerical and physical results of heave decay test, while systematic studies on the heave response and pumping performance under the action of regular waves are completed through the paper. The results demonstrate the importance of nonlinear effects, including viscous drag, wave overtopping and the interaction between heave and pitch modes. Moreover, the study shows also that nonlinear effects significantly decrease the dynamic response of the device and generate a second harmonic for pitch response, increasing the capacity of the OXYFLUX to be overtopped by small waves caused by the summer breeze typical of the hypoxic events
CFD investigations of OXYFLUX device, an innovative wave pump technology for artificial downwelling of surface water
No full textNo other environmental variable of such ecological importance to estuarine and coastal marine ecosystems around the world has changed so drastically, in such a short period of time, as dissolved oxygen in coastal waters. The prevalent methods for counteracting anoxic sea events are indirect measures which aim to cut-down anthropic loads introduced in river and marine environments. To date, no direct approaches, like artificial devices have been investigated except the WEBAP and OXYFLUX devices. The present paper adopts a numerical approach to the analysis of the pumped surface water as well as the analysis of the dynamic response of the OXYFLUX device. By means of a CFD-RANS code and through the application of overset grid method, the 1/16 OXYFLUX model's dynamic response and pumping performance are evaluated. The appropriate grid is selected after an extensive sensitivity analysis carried out on 9 different grids. The CFD model is validated by comparing numerical and physical results of heave decay test, heave response, and surface water discharge under the action of regular waves. The extensive comparison with experimental results shows consistently accurate predictions. The main findings of the study show that nonlinear effects remarkable reduce the dynamic behaviour of the OXYFLUX and generate an unexpected second harmonic for pitch response intensifying the overtopping discharge also for small waves caused by the summer's low intensity winds
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
Wave simulation for the design of an innovative quay wall: the case of Vlorë Harbour
Full text linkSea states and environmental conditions are basic data for the
design of marine structures. Hindcasted wave data have been applied here
with the aim of identifying the proper design conditions for an innovative
quay wall concept.
In this paper, the results of a computational fluid dynamics model are used to
optimise the new absorbing quay wall of Vlorë Harbour (Republic of
Albania) and define the design loads under extreme wave
conditions. The design wave states at the harbour entrance have been
estimated analysing 31 years of hindcasted wave data simulated through the
application of WaveWatch III. Due to the particular geography and topography
of the Bay of Vlorë, wave conditions generated from the north-west are
transferred to the harbour entrance with the application of a 2-D spectral wave
module, whereas southern wave states, which are also the most critical for
the port structures, are defined by means of a wave generation model,
according to the available wind measurements. Finally, the identified extreme
events have been used, through the NewWave approach, as boundary conditions
for the numerical analysis of the interaction between the quay wall and the
extreme events. The results show that the proposed method, based on
numerical modelling at different scales from macro to meso and to micro,
allows for the identification of the best site-specific solutions, also for a
location devoid of any wave measurement. In this light, the objectives of
the paper are two-fold. First, they show the application of sea condition
estimations through the use of wave hindcasted data in order to properly
define the design wave conditions for a new harbour structure. Second, they
present a new approach for investigating an innovative absorbing quay wall based
on CFD modelling and the NewWave theory
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
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
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