1,720,968 research outputs found
CFD modelling coupled with floating structures and mooring dynamics for offshore renewable energy devices using the Proteus simulation toolkit
No full textIn this work, the coupling of novel opensource tools for simulating two-phase incompressible flow problems with fluid-structure interaction and mooring dynamics is presented. The open-source Computational Fluid Dynamics (CFD) toolkit Proteus is used for the simulations. Proteus solves the two phase Navier-Stokes equations using the Finite Element Method (FEM) and is fully coupled with an Arbitrary Lagrangian-Eulerian (ALE) formulation for mesh motion allowing solid body motion within the fluid domain. The multi-body dynamics solver, Chrono, is used for calculating rigid body motion and modelling dynamics of complex mooring systems. At each time step, Proteus computes the forces from the fluid acting on the rigid body necessary to find its displacement with Chrono which will be used as boundary conditions for mesh motion. Several verification and validation cases are presented here in order to prove the successful coupling between the two toolkits aforementioned. These test cases include wave sloshing in a tank, floating body dynamics under free and wave-induced motion for different degrees of freedom (DOFs), and mooring dynamics using beam element theory coupled with rigid body dynamics and collision detection. The successful validation of each component shows the potential of the coupled methodology to be used for assisting the design of offshore renewable energy devices
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
Numerical simulation of the three-dimensional turbulent flow induced by breaking waves in the coastal surf zone
No full textA method named Large Wave Simulation is presented, for the study of turbulent flow that develops during wave breaking (spilling breakers) over a constant-slope bed. According to LWS method, large scales of velocity field and free-surface elevation are numerically resolved, whereas the corresponding subgrid scale (SGS) effects are accounted for by a SGS stress model, equivalent to the ones used in Large Eddy Simulation (LES) method. Spilling breaking is simulated by a SGS stress field that creates an eddy breaker and produces spanwise vorticity at the breaking wave front. LWS method is used in conjuction with the Euler equation and the corresponding nonlinear boundary conditions. Moreover, as a reference, a surface roller (SR) model is used for the simulation of spilling breaking, which necessitates empirical parameters, for the calculation of the eddy breaker effect. The SR model is adapted for two-dimensional, inviscid but rotational free-surface flow, by use of appropriately modified boundary conditions. Results of two-dimensional flow during breaking waves, propagating perpendicularly to the shoreline, are presented, as well as results of threedimensional flow during breaking waves, propagating perpendicularly and obliquely to the shoreline. In the case of waves breaking perpendicularly to the shoreline over a constant slope (1/35) bed, free-surface elevation and velocities results are in accordance with existing experimental data. However, despite of the flow being weakly dependent to the cross-shore direction, due to the fact that the eddy breaker is three-dimensional, LWS method performs better when combined with a three-dimensional flow field. Finally, oblique wave propagation (42,45o at deep water) and breaking over a constant-slope (1/35) bed is simulated. Wave crestlines break gradually and the effect of the SGS stress field produces spanwise (longshore) and streamwise (cross-shore) vorticity. The eddy breaker develops along the breaking wave front and its orientation follows the shape of the breaking crestlines.Στην παρούσα διατριβή παρουσιάζεται η αριθμητική μέθοδος προσομοίωσης μεγάλων κυμάτων (LWS), για τη μελέτη της τυρβώδους ροής που αναπτύσσεται κατά τη θραύση κυμάτων (θραύση εκχείλισης) πάνω από πυθμένα σταθερής κλίσης. Κατά τη μέθοδο LWS, οι μεγάλες κλίμακες των τυρβωδών διακυμάνσεων της ταχύτητας και της ελεύθερης επιφάνειας επιλύονται αριθμητικά, ενώ η επίδραση των μικρών κλιμάκων λαμβάνeται υπόψη με τη χρήση υποπλεγματικού (subgrid scale ή SGS) μοντέλου τάσεων, αντίστοιχο της μεθόδου προσομοίωσης μεγάλων δινών LES. Η θραύση εκχείλισης προσομοιώνεται από τη δράση των SGS τάσεων, οι οποίες δημιουργούν το στρόβιλο θραύσης και παράγουν εγκάρσια στροβιλότητα στο μέτωπο του κύματος. Η μέθοδος LWS εφαρμόζεται σε σύζευξη με τις εξισώσεις Euler και των αντιστοίχων μη-γραμμικών οριακών συνθηκών. Επιπλέον, ως σημείο αναφοράς χρησιμοποιείται η προσομοίωση της θραύσης εκχείλισης με μοντέλο επιφανειακού στροβίλου, κατά το οποίο η επίδραση του στροβίλου θραύσης υπολογίζεται εμπειρικά. Το μοντέλο προσαρμόζεται στις εξισώσεις δισδιάστατης μη συνεκτικής ροής, με τη χρήση κατάλληλα τροποποιημένων οριακών συνθηκών. Παρουσιάζονται αποτελέσματα δισδιάστατης ροής, κατά τη θραύση κύματος κάθετα στην ακτογραμμή και τρισδιάστατης ροής, κατά τη θραύση κύματος κάθετα και υπό γωνία ως προς την ακτογραμμή. Γενικά, τα αποτελέσματα της ελεύθερης επιφάνειας και του πεδίου ταχυτήτων στη ζώνη απόσβεσης, κατά την θραύση κυμάτων κάθετα στην ακτογραμμή και πάνω από πυθμένα κλίσης 1/35, δείχνουν ικανοποιητική συμφωνία με τις αντίστοιχες πειραματικές μετρήσεις. Ωστόσο, παρά την ασθενή εξάρτηση της ροής εγκάρσια στην ακτογραμμή, παρατηρείται ότι, λόγω της τρισδιάστατης δομής του στροβίλου, ο μηχανισμός της θραύσης προσομοιώνεται ικανοποιητικότερα από τη μέθοδο LWS, όταν αυτή συνδυάζεται με τρισδιάστατο πεδίο ροής
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
Fluid flow through vegetation
Full text linkThis thesis is concerned with the mechanical aspects of fluid-vegetation interaction in coastal flows and their resultant instabilities. Specifically, we consider the evolution of periodic waves as they propagate through vegetated domains, and the emergence of monami – the progressive, synchronous oscillation of submerged vegetation under sufficiently strong flows. We divide our analysis between rigid and flexible vegetative canopies. These new predictions and physical insights will be applicable in the analysis of a diverse range of industrial and environmental applications involving fluid-vegetation interactions.
In the case of rigid vegetation, using the method of multiple scales, we derive the evolution of small-amplitude waves propagating over a varying substrate fully covered with vegetation. In particular, we give time-averaged predictions for both the amplitude and the wavelength of the waves as functions of the distance of propagation. We then extend this analysis to include the situations of (i) combined current-wave flows and (ii) shallow-water waves through vegetation. For the case of combined current-wave flows, we demonstrate the manner in which the surface waves vary as a function of the current, and also how the current remains unaffected by the evolving wave. For shallow-water waves, we explore how cnoidal waves, nonlinear periodic solutions of the Korteweg-de Vries equation, evolve on horizontal substrates. For all of the flows considered above on rigid vegetation, their evolutions are only drag-dependent and hence independent of added mass and virtual buoyancy.
In the case of flexible vegetation, we propose a model where the plants are described by elastic cantilever beams. Our first analysis concerns the propagation of small-amplitude waves. Compared to the case of rigid vegetation, the fluid will load and deform each vegetative structure. This deformation, in turn, must affect the flow. Although the flow and the beam dynamics have to be determined simultaneously, we show that when the wavelength is sufficiently small, such quantities are asymptotically decoupled -- this allows us to first determine the local beam dynamics before evaluating the momentum loss in the macroscopic flow. In contrast to rigid vegetation, we find that added mass and virtual buoyancy play a role.
Finally, we focus on understanding the mechanisms and critical conditions for triggering monami. We treat the current as unidirectional and solve for the steady configurations of the flow and the deflected canopy. Our stability analysis predicts that monami is induced by shear along the top of the canopy. Meanwhile, monami can be suppressed if the canopy is sufficiently sparse or if there is sufficient inertia in the system
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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