1,720,979 research outputs found
Matrix-free stability analysis of fluid-structure interaction problems with an Immersed Boundary method.
Full text linkThe mutual interaction between viscous fluids and elastic solids plays a role in a variety of engineering applications and natural systems. In some cases, large structural deformations are sought for engineering purposes, at other times undesirable vibrations cause structural damage.
Performing accurate and high-fidelity numerical simulations to investigate the behavior of such fluid-structure interaction (FSI) problems is not trivial nor cheap, thus the development of numerical methods for FSI is a very active research area.
Another possibility is to investigate the linear dynamics of these coupled systems.
Linear stability analysis is a popular tool in the fluid mechanics community since it allows the faster identification of the stability criteria and gives insights into the underlying physics of the phenomena. As a matter of fact, the data resulting from
temporal simulations may be difficult to interpret directly. Besides, it is usually necessary to run long simulations to go past the transient phase and see if a given perturbation fades away.
However, many FSI configurations of engineering relevance are still uninvestigated from a linear point of view due to the complexity of the linearization of the coupled dynamics. The main objective of this thesis is to promote a wide adoption of
the linear approach to FSI problems. An Immersed Boundary (IB) framework is introduced, based on a direct-forcing moving-least-squares procedure to couple the fluid and solid dynamics, which has been already well validated and has proven to
accurately capture the coupled dynamics. The major novelty of the present work is the development of a general approach to perform linear stability analyses of large-scale FSI problems, based on the IB method previously mentioned. To the author’s
knowledge, in the context of FSI systems, the global linear approach has not been yet extended to problems involving multiple elastic bodies. The proposed methodology allows the treatment of multi-body configurations with no added complexity and reasonable computational cost.
In this thesis, the proposed methodology is derived and the numerical solver is validated against results from the literature. Then, the procedure is applied to analyze the vortex-induced vibrations of two elastically mounted cylinders in tandem
arrangement. Two unstable eigenmodes are identified in the analysis, and an explanation is suggested for a change in the nonlinear behavior of the system, previously noted by other researchers but still without interpretation.
In the last chapter, a different methodology is adopted to investigate the linear dynamics of a gas bubble placed in a uniform straining flow. For this case, it is used a recently developed linearized Arbitrary Lagrangian-Eulerian framework. The linear analysis of this configuration reveals the existence of a saddle-node bifurcation linked to the breakup of the bubble via an end-pinching mechanism. Interestingly, a self-propelling unstable mode emerges, which is counterintuitive as it consists
in a displacement of the bubble towards a higher-pressure region. The existence of this mode is confirmed in the inviscid limit, and it is shown that the propulsive mechanism exploits shape asymmetries to create a net thrust
An adjoint-based analysis of the secondary instability of the wake of a circular cylinder
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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
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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