1,720,970 research outputs found
Application of a new OpenFOAM tool to design a pilot floating wind farm offshore mazara del vallo (Italy)
No full textA new Computational Fluid Dynamic tool, based on OpenFOAM, was implemented to reproduce a physical wave tank for offshore applications. The code has new boundary conditions for deep water wave generation, a new turbulent model and a new numerical restraint to represent realistic mooring lines in OpenFOAM. A real study case application of this tool is shown hereby: a preliminary analysis of a floating wind turbine offshore Mazara del Vallo, (Italy). The application demonstrated the usefulness and capability of the model. Moreover, with active absorption, the dimension of the numerical domain, computational costs and time of the simulations are reduced
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
Sediment fluidization system for nautical depth maintenance under monitored environmental currents
No full textOceanic ships are getting larger and costs of dredging are increasing, which largely justify the research on new practices for harbour entrance maintenance. In fact, the sedimentation of sands transported along coast reduces the navigable depth and requires a continuous dredging to ensure the entry of the vessels in secure conditions.
As new practice for reducing the dredging operations it is proposed a sediment fluidization system, which can maintain the required water depth by pumping water under the bed of the port entrance. Conditions to cause the sediment/fluid mixture to behave as a fluid could be achieved by the introduction of pressurized sea water through the sediment deposition. This results in heavily loaded fluid that can be removed by environmental currents. In this way erosion and deposition can be driven to maintain nautical depth and on the basis of monitored environmental currents.
Sand fluidization as opposite to sediment dewatering could be applied to mobilize depositions in the intertidal zones, when suitable currents take place to remove low depths barrier to navigation and harbour entrance. In the chemical industry the fluidization is usually realized within reactors, while, in the case of nautical depth maintenance, pump systems similar to dewatering system could be applied and controlled by means of Acoustic Doppler Current Profilers (ADCP) to monitor tidal and long shore currents.
A first application of the fluidization system was made on the commercial harbour of Ravenna (Italy), by means of the numerical code Mik21, to study the sediment transport near the port entrance. Ravenna represents the only commercial port of the Emilia Romagna Region and, thanks to its geographical position, is a leader in Italy for trade with the East Mediterranean Sea and the Black Sea, and also plays an important role for trade with the Middle and Far East. A first analysis indicates that the fluidization system can be used instead of dredging operations for removing the clean sediments from the entrance of the harbour by means of coastal currents
Optimal index related to the shoreline dynamics during a storm: the case of Jesolo beach
Full text linkThe paper presents an application of shoreline monitoring aimed at
understanding the response of a beach to single storms and at identifying its
typical behaviour, in order to be able to predict shoreline changes and to
properly plan the defence of the shore zone. On the study area, in Jesolo
beach (northern Adriatic Sea, Italy), a video monitoring station and an
acoustic wave and current profiler were installed in spring 2013, recording,
respectively, images and hydrodynamic data. The site lacks previous detailed
hydrodynamic and morphodynamic data.
Variations in the shoreline were quantified in combination with available
near-shore wave conditions, making it possible to analyse the relationship
between the shoreline displacement and the wave features. Results denote
characteristic patterns of beach response to storm events, and highlight the
importance of improving beach protection in this zone, notwithstanding the
many interventions experimented in the last decades. A total of 31
independent storm events were selected during the period October
2013–October 2014, and for each of them synthetic indexes based on storm
duration, energy and maximum wave height were developed and estimated. It was
found that the net shoreline displacements during a storm are well correlated
with the total wave energy associated to the considered storm by an empirical
power law equation. A sub-selection
of storms in the presence of an artificial dune protecting the beach (in the
winter season) was examined in detail, allowing to conclude that the adoption
of this coastal defence strategy in the study area can reduce shoreline
retreat during a storm. This type of intervention can sometimes contribute to
prolonging overall stability not only in the replenished zone but also in
downdrift areas.
The implemented methodology, which confirms to be economically attractive if
compared to more traditional monitoring systems, proves to be a valuable
system to monitor beach erosive processes and provide detailed indications on
how to better plan beach-maintenance activities. The presented methodology
and the proposed results can therefore be used as a basis for improving the
collaboration between coastal scientists and managers to solve beach erosion
problems, in locations where data are scattered and sporadic.</p
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
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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