1,720,961 research outputs found
A set of canonical problems in sloshing. Part 2: Influence of tank width on impact pressure statistics in regular forced angular motion
Get PDFContinuing along the path of previous papers in this series, the present paper addresses, experimentally, sloshing in a rectangular tank under harmonic angular forcing. Since lateral and roof impacts are relevant in sloshing assessment and present distinct dynamics, these have been studied. Water and oil have been used in order to obtain data for high and moderate Reynolds numbers. With the aim of addressing effects induced by the three-dimensionality of the flow, a study of the influence of the tank width on pressure statistics has also been conducted. For this purpose, a tank which can be adjusted to 4 different widths by replacing the side plates was built. For each combination of fluid, tank width and filling level, a total of 120 experiments, each comprising 120 peaks, have been conducted, allowing an analysis in time and ensemble domains to be performed. Impact pressure statistics are presented including mean values, percentiles, and exceedance probability graphs
Three SPH Novel Benchmark Test Cases for free surface flows
No full textAbstract—Benchmark Test Cases have been used by SPHERIC interest group members for the validation of SPH models and their corresponding computer implementations. Since the use of SPHERIC benchmark test cases as validation reference for SPH implementations has slightly declined in the most recent editions,
we think it might be interesting to document three novel test cases with the aim of enriching the database with complementary validation data. The first proposed test case is a wave impact problem in a rectangular tank. The time history of the motion
of the tank and the pressure of the first instances of lateral and roof impacts for both water and oil are provided. An analysis of the two-dimensionality and repeatability of the pressure peaks is provided. The second proposed test case treats the coupling
of the angular motion of a sloshing tank and a single degree of freedom structural system. Finally, the third proposed test case, is a canonical fluid structure interaction problem consisting in the interaction between a free surface sloshing flow and an elastic body. As both SPH practitioners and experimentalists, regardless of the discussion provided in this paper, we are committed to improving these test cases for future use. We hope to increase our experimental skills and capabilities not only in light of experience from our own simulations but mainly by receiving a feedback
from the SPH community
Smoothed particle hydrodynamics (SPH) simulation of a tuned liquid damper(TLD) with angular motion.
Get PDFThe roll motion response of a single degree of freedom (SDOF) structural system to which a rigid rectangular partially filled liquid tank has been attached is considered. The SDOF structural system with the empty tank is first described with a mathematical model and this model is validated by performing decay experiments as well as experiments in which periodic excitations are applied to the system. The responses are accurately predicted by the model. The accuracy of these predictions allows us to study both experimentally and numerically, with weakly compressible SPH, the performance of the partially filled tank as a tuned liquid damper (TLD). The sloshing flows inside the tank comprise the onset of breaking waves which make the TLDs devices extremely difficult to model, especially for the potential flow multimodal approaches commonly used to simulate these sorts of coupled systems. In order to characterise the wave breaking effects on the response curves, tests have been performed with liquids of different viscosity, the increasing viscosity preventing the onset of breaking waves. The capabilities of SPH to treat this coupling problem are assessed and the results show that SPH is able to capture a substantial part of the physics involved in the addressed phenomena but further work remains still to be done relating to a more accurate treatment of the laminar viscosity and turbulence effects
Hydrodynamic coefficients from forced and decay heave motion tests of a scaled model of a column of a floating wind turbine equipped with a heave plate
Get PDFThis paper describes the results of an experimental campaign aimed at the determination of heave hydrodynamic coefficients for a column of a floating wind turbine platform, equipped with a solid heave plate. The tests are carried out with an experimental system that allows performing both heave forced oscillation tests and heave decay tests. A specific characteristic of the system is the reduced mechanical friction, thanks to the use of air bushings. A series of forced oscillation and decay experiments have been carried out with such a model, and the hydrodynamic coefficients obtained in both types of tests are compared. Results show correlation between both methods if the mean of the peaks of the decay process is chosen to represent its Keulegan–Carpenter number (KC), with a fair matching of the results in the KC range where both methods are applicable. With the objective of conducting an uncertainty assessment which can be relevant for the full-scale extrapolation of results, non-dimensional added mass and damping coefficients are proposed. They incorporate the primitive relevant variables and are shown to lead to a notable collapse of the various results in the form of curves with small differences among them. With these coefficients, an uncertainty assessment is carried out, propagating to those coefficients the uncertainties of the primitive variables in place. Such non-dimensional coefficients are useful to develop simple models to estimate the dimensional ones to be used in numerical simulations of the full scale system. The estimated uncertainties can serve to define design safety margins for the values of such coefficients
A combined Experimental and SPH Approach to Sloshing and Ship Roll Motions
No full textPassive anti-roll tanks have been used for a long time in ships to damp their roll motion. The coupled roll motion response of a single degree of freedom (SDOF) system to which a passive anti-roll tank has been attached is considered in the present paper. The performance of the anti-roll tank has been studied both experimentally and numerically, with weakly compressible SPH. The sloshing flows inside the tank comprise the onset of breaking waves. In order to characterise the wave breaking effects on the response curves, tests have been performed with liquids of different viscosity, the increasing viscosity preventing the onset of breaking waves. The capabilities of SPH to treat this coupling problem are assessed and the results show that SPH is able to capture a part of the physics involved in the addressed phenomena but further work remains still to be done
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
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