1,720,962 research outputs found
The development of a dissipative potential flow model for wave making resistance prediction
No full textSteady ship motion in calm water is a classical problem in ship hydrodynamics. Potential flow modelling is a common method to predict the wave resistance of ships. In its conventional form the flow is assumed to be free from damping due to the inviscid assumption of potential flow. It has been argued by the founding fathers of ship resistance predictions that damping plays an important role in determining the wave resistance. Despite this viscosity is often omitted from present wave resistance prediction methods. It is known that damping plays an important role in the formation of the wave pattern and it is therefore of interest to determine the effect on the resistance prediction by including a damping factor in a previously undampened model.In this study, the problem is modelled using Kelvin sources with a translating speed. The fluid flow is modelled using a linearised free surface condition but an exact body condition on the hull. Rayleigh damping is introduced in the model to emulate viscous damping. To calculate the source influences, a new dissipative 3D Green function is derived. The image source part of Green function is separated into the near field and far field disturbance to achieve fast convergence of the integrals.The method is evaluated using thin ship theory to determine the wave pattern behind and the wave profile along a Wigley hull. A panel method is used to determine the wave and residual resistance for submerged ellipsoids and spheres. The results are validated and compared to existing numerical and experimental data from other sources. The results show that it may be possible to capture the residual resistance by including damping in a potential flow model but that more evaluations are needed
The key to successful carbon capture and storage: engaging the public
No full textThis book is written during the LRET Summer Collegium 2011 held in the University of Southampton. In recognition to the need to reduced CO2 emission from coal or fuel fired power plant, research project on an engineering system for carbon capture and storage (CCS) in ocean space utilisation is proposed in the collegium. This book is written to address the engineering challenges in our proposed CCS engineering system. It is recognised that the public perception is the main key to successful CCS project and an engineering system that involves public engagement in the CCS project in the early stage is proposed. The proposed project is known as the “Green Town” where it comprises of an air scrubbing towers that has the ability to capture CO2 from the air. The selected site for the case study would then be free of anthropogenic CO2. The captured CO2 will then be transported by pipelines and stored in depleted oil/gas field for a geological time scale. Hamburg in Germany is selected as the case study city since it is a port city and is close to available geological formations for CO2 storage. The K12-B gas field has also been identified as the proposed sequestration site. The CO2 pipelines will tie-in to existing gas pipelines when they are no longer in use in the near future and the CO2 injection system for the CO2 will be retrofitted to gas platform when the gas field is no longer in use. The cost, risk and legal issues for the proposed “Green Town” idea are also addressed as well. This project also designed and conducted specific surveys in Southampton and Hamburg to investigate the public perception towards the “Green Town” idea and CCS. Unique findings are found and presented in this book. This book makes an important contribution in addressing the need to engage the public at the early stage of the CCS project. The designed surveys successfully proved that the proposed “Green Town” idea could act as an effective ‘door opener’ to future CCS project. We hope that this book would be useful to engineers and scientists working on the areas of CCS and are looking forward to share our views on the unique findings about the public’s perception of CCS
Numerical Simulation of the Effect of Wave Characteristics on PTO of Point Absorber Wave Energy Converter
Get PDFThe ocean is currently an extremely large and under-developed source of renewable energy. The recent interest in the Blue Economy has led the scientific community to increase investigations in sustainable oceanic energy options, such as Point Wave Energy Converters (WEC). These devices harvest the wave energy using the excited oscillatory motion of the buoy, which is connected to a Power Take-Off system (PTO). During the last decades, the development of these devices has been boosted but they are still behind other renewable energy technologies. The Furthlab at Texas A&M University has showed that the spheroid buoy shape with a low length to diameter ratio is a good candidate shape to extract wave energy, by testing different buoy shapes and aspect ratios at a non-linear Stokes-II wave generation. This paper is the next step in our investigations and numerically investigates the effect of changing the wave characteristics, such as amplitude, frequency, and speed on the power-generating ability of the spheroid buoy system. Three dimensional Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations of the selected buoy were performed in OpenFOAM with the integration of a dynamic mesh module to handle the heave motion of the buoy. In addition, the PTO system was compensated with a forced oscillator mechanism of spring and damper. A comparison between the buoy���s displacement and frequency responses, and power efficiency showed the optimal operating sea state to maximize energy output using the spheroid WEC. The results conclude that the best wave conditions to maximize the power extraction efficiency using a spheroid buoy with a diameter of 1 m and length of 0.5 m are wave length greater than 4 m, wave height less than 0.15 m, and wave speed between 0.07 and 0.12 m/s
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
Temperature-Compensated Calibration and Measurements with Cross-Style Hotwire Anemometers
Get PDFFlow field measurements collected using constant-temperature hotwire anemometers (CTAs) are known to be sensitive to variation in the ambient fluid temperature. Various calibration techniques are detailed in literature for temperature compensation of single-component velocity measurements using single-normal hotwires. However, a rigorous methodology has not yet been defined for temperature compensation in two-component velocity measurements using cross-style hotwires. This research defines a procedure for the calibration of cross-style hotwires from which temperature compensated estimates of the streamwise, U, and spanwise, W, components of the local velocity are obtained. To map the effects of ambient temperature, flow angularity, and velocity magnitude to hotwire voltages, a series of four calibration sweeps is conducted at the beginning of each day of operation. Resulting velocity component accuracy is analyzed for several known flow angle, temperature, and velocity magnitude combinations in the freestream. Based on the study���s results, model form errors in the hotwire responses are known a priori for general experiments to remain under 2% for measurements taken within the bounds of the calibration probe angle range while component uncertainties are determined for the included experiment a posteriori to range up to ��1.1% of the measured velocity magnitude and within ��0.6�� of the measured flow angle. Comparisons of cross-style and single-normal hotwire flat-plate boundary layer measurements in the wake of a vortex generator demonstrate excellent agreement in the streamwise component estimates
Development and Conduction of an Experiment to Investigate the Static Friction Interactions Between a Wooden Crosstie and Ballast Material
Get PDFThe focus of this research is on the friction interactions between railroad crossties and ballast material. These friction interactions change over time as the crossties experience continued loading due to passing trains. In order to investigate this topic, an experiment has been designed to observe the static friction coefficient, points of contact, and contact area between a crosstie and ballast material. The question arises as to whether there is a correlation between these factors and the number of loading cycles. The data collected in this experiment will be useful in ocean engineering applications such as the design of a seawall structure against a sand berm. This experiment was performed as part of a larger research effort examining railroad track buckling
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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