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Author: Junhui Lou
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 174
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Book Description
This dissertation studies the coupled fluid-structure interaction (FSI) of a wave energy converter (WEC) and evaluates the design of a WEC mooring system. The research is conducted in support of conceptual development, field test and performance evaluation of WECs as part of the mission of the Northwest National Marine Renewable Energy Center at Oregon State University. The coupled FSI study focuses on the evaluation of predictive capabilities and computational performance of commercial computational fluid dynamics (CFD) and potential flow codes using laboratory model test results. The evaluations of a WEC mooring system focus on analysis of field test data and evaluations of the anchor movability, fatigue design and extreme load of the Ocean Sentinel (OS) test platform mooring system deployed off the Oregon coast. Numerical data using a commercial mooring system simulation code are conducted to supplement time history data for the calculations of anchor pulling force, fatigue damage and extreme load. Specifically, this dissertation can be divided into three parts. In the first part the performances of a finite element explicit Navier-Stokes (NS) solver (LS-DYNA ALE), a finite element implicit NS solver (LS-DYNA ICFD), and a nonlinear potential flow solver (AQWA) in predicting highly nonlinear hydrodynamic responses of a floating point absorber (FPA) under large-amplitude waves are studied. The two NS solvers calculate the coupled FSI including fully nonlinear inviscid and viscous forces. The nonlinear potential flow solver calculates individual inviscid wave force components (a Froud-Krylov force, a radiation force, a diffraction force and a hydrostatic force) and empirical (Morison equation) viscous force. Comparing numerical results to laboratory experimental measurements, the two NS solvers and the nonlinear potential flow solver are found to be capable of providing accurate predictions of the nonlinear motion responses of the FPA. FSI coupling algorithms and computational costs of these three solvers are evaluated. Based on the results of the nonlinear potential flow solver at different wave periods, the individual wave force components and the viscous force are studied quantitatively. The nonlinearity of the restoring force and the Froude-Krylov force are found to be important for the FPA responses in all (heave, surge and pitch) directions; the nonlinearity of the viscous force is found to be important in only the heave and pitch directions. The second part first presents a catenary spread mooring system design of a mobile ocean test berth (MOTB), the Ocean Sentinel (OS) instrumentation buoy, which is developed by the Northwest National Marine Renewable Energy Center (NNMREC) to facilitate ocean test of wave energy converters (WECs). Then the OS mooring design, which is similar to a conventional WEC point absorber mooring system, is evaluated through both field test analysis and quasi-static analysis: the field test analysis is based on the extensive data of the OS positions, mooring tensions on the OS and environmental conditions of waves, wind and current, collected during the 2013 field test of the OS mooring system; the quasi-static analysis is based on the analytical catenary equations of mooring chains. Both global characteristics and survivability characteristics of the mooring system are evaluated: the global characteristics include the influence of the OS excursion to mooring tension, positional distribution of the OS, directional control of the OS and environmental contributions of waves, current and wind to mooring tensions; the survivability characteristics include the anchor movability and strength capacities of mooring. Because anchor movement occurred near the end of the field test, a systematic procedure of designing a mooring system with adequate anchor holding capacity is developed and applied to design a new OS mooring system. In the third part, first, the accuracies of a fully coupled method based numerical model in predicting the mooring tensions of the OS mooring system and the OS positions are validated by comparing the numerical results to the field data collected during the 2013 OS field test. Then, the anchor movability, fatigue damage and extreme mooring tension of the OS mooring system are investigated using the mooring tensions predicted by the numerical model. The results of the above studies are summarized as follows: (1) The numerical model provides accurate predictions of the mooring tensions and OS positions under harsh environmental conditions; (2) When the OS drifted significantly near the end of the field test, the bow, port and starboard anchors were likely not dragged, dragged significantly and dragged slightly, respectively; (3) The fatigue damages of mooring lines are predicted for environmental conditions from low to high sea states; and (4) The strengths of mooring lines in the original mooring design are adequate compared to the predicted extreme mooring tensions.
Author: Junhui Lou
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 174
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Book Description
This dissertation studies the coupled fluid-structure interaction (FSI) of a wave energy converter (WEC) and evaluates the design of a WEC mooring system. The research is conducted in support of conceptual development, field test and performance evaluation of WECs as part of the mission of the Northwest National Marine Renewable Energy Center at Oregon State University. The coupled FSI study focuses on the evaluation of predictive capabilities and computational performance of commercial computational fluid dynamics (CFD) and potential flow codes using laboratory model test results. The evaluations of a WEC mooring system focus on analysis of field test data and evaluations of the anchor movability, fatigue design and extreme load of the Ocean Sentinel (OS) test platform mooring system deployed off the Oregon coast. Numerical data using a commercial mooring system simulation code are conducted to supplement time history data for the calculations of anchor pulling force, fatigue damage and extreme load. Specifically, this dissertation can be divided into three parts. In the first part the performances of a finite element explicit Navier-Stokes (NS) solver (LS-DYNA ALE), a finite element implicit NS solver (LS-DYNA ICFD), and a nonlinear potential flow solver (AQWA) in predicting highly nonlinear hydrodynamic responses of a floating point absorber (FPA) under large-amplitude waves are studied. The two NS solvers calculate the coupled FSI including fully nonlinear inviscid and viscous forces. The nonlinear potential flow solver calculates individual inviscid wave force components (a Froud-Krylov force, a radiation force, a diffraction force and a hydrostatic force) and empirical (Morison equation) viscous force. Comparing numerical results to laboratory experimental measurements, the two NS solvers and the nonlinear potential flow solver are found to be capable of providing accurate predictions of the nonlinear motion responses of the FPA. FSI coupling algorithms and computational costs of these three solvers are evaluated. Based on the results of the nonlinear potential flow solver at different wave periods, the individual wave force components and the viscous force are studied quantitatively. The nonlinearity of the restoring force and the Froude-Krylov force are found to be important for the FPA responses in all (heave, surge and pitch) directions; the nonlinearity of the viscous force is found to be important in only the heave and pitch directions. The second part first presents a catenary spread mooring system design of a mobile ocean test berth (MOTB), the Ocean Sentinel (OS) instrumentation buoy, which is developed by the Northwest National Marine Renewable Energy Center (NNMREC) to facilitate ocean test of wave energy converters (WECs). Then the OS mooring design, which is similar to a conventional WEC point absorber mooring system, is evaluated through both field test analysis and quasi-static analysis: the field test analysis is based on the extensive data of the OS positions, mooring tensions on the OS and environmental conditions of waves, wind and current, collected during the 2013 field test of the OS mooring system; the quasi-static analysis is based on the analytical catenary equations of mooring chains. Both global characteristics and survivability characteristics of the mooring system are evaluated: the global characteristics include the influence of the OS excursion to mooring tension, positional distribution of the OS, directional control of the OS and environmental contributions of waves, current and wind to mooring tensions; the survivability characteristics include the anchor movability and strength capacities of mooring. Because anchor movement occurred near the end of the field test, a systematic procedure of designing a mooring system with adequate anchor holding capacity is developed and applied to design a new OS mooring system. In the third part, first, the accuracies of a fully coupled method based numerical model in predicting the mooring tensions of the OS mooring system and the OS positions are validated by comparing the numerical results to the field data collected during the 2013 OS field test. Then, the anchor movability, fatigue damage and extreme mooring tension of the OS mooring system are investigated using the mooring tensions predicted by the numerical model. The results of the above studies are summarized as follows: (1) The numerical model provides accurate predictions of the mooring tensions and OS positions under harsh environmental conditions; (2) When the OS drifted significantly near the end of the field test, the bow, port and starboard anchors were likely not dragged, dragged significantly and dragged slightly, respectively; (3) The fatigue damages of mooring lines are predicted for environmental conditions from low to high sea states; and (4) The strengths of mooring lines in the original mooring design are adequate compared to the predicted extreme mooring tensions.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A wave-energy-converter-specific time-domain modeling method (WEC-Sim) was coupled with a lumped-mass-based mooring model (MoorDyn) to improve its mooring dynamics modeling capability. This paper presents a verification and validation study on the coupled numerical method. First, a coupled model was built to simulate a 1/25 model scale floating power system connected to a traditional three-point catenary mooring with an angle of 120 between the lines. The body response and the tension force on the mooring lines at the fairlead in decay tests and under regular and irregular waves were examined. To validate and verify the coupled numerical method, the simulation results were compared to the measurements from a wave tank test and a commercial code (OrcaFlex). Second, a coupled model was built to simulate a two-body point absorber system with a chain-connected catenary system. The influence of the mooring connection on the point absorber was investigated. Overall, the study showed that the coupling of WEC-Sim and the MoorDyn model works reasonably well for simulating a floating system with practical mooring designs and predicting the corresponding dynamic loads on the mooring lines. Further analyses on improving coupling efficiency and the feasibility of applying the numerical method to simulate WEC systems with more complex mooring configuration are still needed.
Author: Aaron K. Porter
Publisher:
ISBN:
Category : Ocean wave power
Languages : en
Pages : 106
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Book Description
This thesis investigates the effects of wave energy converters (WECs) on water waves through the analysis of extensive laboratory experiments, as well as subsequent numerical simulations. Data for the analysis was collected during the WEC-Array Experiments performed at the O.H. Hinsdale Wave Research Laboratory at Oregon State University, under co-operation with Columbia Power Technologies, using five 1:33 scale point-absorbing WECs. The observed wave measurement and WEC performance data sets allowed for a direct computation of power removed from the wave field for a large suite of incident wave conditions and WEC array sizes. To numerically represent WEC effects the influence of the WECs upon the wave field was parameterized using the power absorption data from the WECs. Because a large driver of the WECs influence on the wave field is absorbed wave power by the WEC, it is reasonable to attempt a parameterization based on this process. It was of interest as to whether this parameterization, which does not account for wave scattering among other physics, could provide a good estimate of far-field effects. Accurately predicting WEC-array effects in the far-field requires empirical validation. Previous WEC analysis and modeling studies had limited data available for model verification, and additionally had used idealized WEC performance. In the present work we develop a WEC-array parameterization for use in phase-averaged wave models (e.g. SWAN). This parametrization only considers the wave absorption effects of the WECs and the model predictions of far-field effects are compared to observations. Further testing of the SWAN model was performed against a phase-resolving model, WAMIT, to determine the significance of physics the WEC absorption parameterization does not capture, such as scattered waves. Considering the complexity of the problem, the parameterization of WECs by only power absorption is a reasonable predictor of the effect of WECs on the far field.
Author: Eduard Foved Johe
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
In the current scenario of exhaustion of fossil fuels, new forms of alternative energy must gain ground. Taking advantage of the great amount of water, the element that gives name to our planet (blue planet); this thesis is focused on one of the ways to extract energy from water: using the waves motion in order to generate electricity. The aim of this thesis is to collaborate in a project of a Wave Energy Converter developed by a group of researchers of Politecnico di Torino. Specifically, much of the study will focus on the design a mooring system for the Wave Energy Converter and integrate it to the linear model of the system. First of all, in the first chapter an overview of the energy consumption problem is given. It is also commented the need of using renewable sources and some of them are presented. In chapter two, it is presented the wave power as a possible clean energy source. It is also explained with numerical values the great viability of this source both globally and in Europe. Finally, some sea characteristics of the region where the Wave Energy Converter will be placed (Mediterranean Sea, Pantelleria) are also commented. Then in chapter three, the concept of a Wave Energy Converter is described. Two different ways to classify these devices are given and some existent Wave Energy Converters projects are presented. In chapter four it is presented the Wave Energy Converter studied in this thesis: the PEWEC (PEndulum Wave Energy Converter). Its working principle it is briefly remarked and some aspects of the mechanism that makes the energy conversion (the pendulum) are commented. Chapter five is focused on one of the main goals of this thesis: the mooring system. Firstly, a presentation of the objectives, requirements, different configurations and components of a mooring system is given. Then, the PEWEC's mooring system is described: its design, the integration of the mooring system into the PEWEC's linear model and the obtaining of the mooring stiffness and parameters. In chapter six, the 1:45 PEWEC prototype is fully described. Its components are named and are explained. This work is done by comparing the SolidWorks drawings with real images of the prototype. Chapter seven is focused on the description of the PEWEC's linear model. It will be commented its parameters and the linear model will be launched. The results of the simulation will be presented and analyzed. In order to facilitate the analysis, a graphic data analysis will be developed. Then in chapter eight, the tests carried out in Rome with the 1:45 prototype are explained. The testing facilities and the different tests developed are described and the data collected is analyzed. In chapter nine, it will be possible to develop a first comparison between the linear model simulation and the testing results. Finally, the last part consists in a conclusion of all the work developed in this thesis. It will be possible to extract some conclusions about the comparison between the linear model and the testing results. At the end of this document it is possible to find an annex with extra information of the work developed, such as parts of Matlab code. It is important to comment that this thesis is focused in the 1:45 prototype. However, in parallel it has been developing the 1:12 prototype. The 1:12 prototype is expected to be tested during July 2015. All the study developed in the mooring system for the 1:45 prototype can also be useful for the 1:12 prototype, with a necessary adaptation of the parameters.
Author: Srinivasan Chandrasekaran
Publisher: CRC Press
ISBN: 1000571483
Category : Science
Languages : en
Pages : 273
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Book Description
Designing offshore wave energy converter (WEC) devices requires a thorough understanding of many aspects of science and engineering, namely, wave hydrodynamics, wave-WEC interactions, mechanical design, analysis tools, and conducting experiments. This book provides the tools for understanding these complex systems and addresses the basic concepts of WECs through detailed analysis and design. A few devices developed and experimentally investigated are discussed in detail, some of which are considered highly novel and still in the preliminary stages of study in the existing literature. FEATURES Offers numerous detailed design methods and practical model studies Presents analysis of the dynamic response behavior of WECs based on experimental studies on scale models Covers the most recent and novel innovations in the field Includes a discussion of offshore wind farms as a green energy alternative and examines their conceptual development and design This book serves as a useful guide for both academicians and professionals in naval architecture and offshore engineering as well as in civil and structural engineering. In addition, it helps in the understanding of structural behavior in terms of risk criteria, efficiency, service life, and reliability. Readers will gain a comprehensive knowledge of the design and development of offshore wave energy devices and the preliminary design of offshore wind turbines, which are currently largely absent in the scientific literature.
Author: Matt Folley
Publisher: Academic Press
ISBN: 0128032111
Category : Technology & Engineering
Languages : en
Pages : 308
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Book Description
Numerical Modelling of Wave Energy Converters: State-of-the Art Techniques for Single WEC and Converter Arrays presents all the information and techniques required for the numerical modelling of a wave energy converter together with a comparative review of the different available techniques. The authors provide clear details on the subject and guidance on its use for WEC design, covering topics such as boundary element methods, frequency domain models, spectral domain models, time domain models, non linear potential flow models, CFD models, semi analytical models, phase resolving wave propagation models, phase averaging wave propagation models, parametric design and control optimization, mean annual energy yield, hydrodynamic loads assessment, and environmental impact assessment. Each chapter starts by defining the fundamental principles underlying the numerical modelling technique and finishes with a discussion of the technique's limitations and a summary of the main points in the chapter. The contents of the chapters are not limited to a description of the mathematics, but also include details and discussion of the current available tools, examples available in the literature, and verification, validation, and computational requirements. In this way, the key points of each modelling technique can be identified without having to get deeply involved in the mathematical representation that is at the core of each chapter. The book is separated into four parts. The first two parts deal with modelling single wave energy converters; the third part considers the modelling of arrays; and the final part looks at the application of the different modelling techniques to the four most common uses of numerical models. It is ideal for graduate engineers and scientists interested in numerical modelling of wave energy converters, and decision-makers who must review different modelling techniques and assess their suitability and output. - Consolidates in one volume information and techniques for the numerical modelling of wave energy converters and converter arrays, which has, up until now, been spread around multiple academic journals and conference proceedings making it difficult to access - Presents a comparative review of the different numerical modelling techniques applied to wave energy converters, discussing their limitations, current available tools, examples, and verification, validation, and computational requirements - Includes practical examples and simulations available for download at the book's companion website - Identifies key points of each modelling technique without getting deeply involved in the mathematical representation
Author: Deborah Greaves
Publisher: John Wiley & Sons
ISBN: 1119014476
Category : Science
Languages : en
Pages : 761
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Book Description
Eine umfassende Publikation zu sämtlichen Aspekten der Wellen- und Gezeitenenergie. Wave and Tidal Energy gibt einen ausführlichen Überblick über die Entwicklung erneuerbarer Energie aus dem Meer, bezieht sich auf die neueste Forschung und Erfahrungen aus Anlagentests. Das Buch verfolgt zwei Ziele, zum einen vermittelt es Einsteigern in das Fachgebiet eine Überblick über die Wellen- und Gezeitenenergie, zum anderen ist es ein Referenzwerk für komplexere Studien und die Praxis. Es vermittelt Detailwissen zu wichtigen Themen wie Ressourcencharakterisierung, Technologie für Wellen- und Gezeitenanlagen, Stromversorgungssysteme, numerische und physikalische Modellierung, Umwelteffekte und Politik. Zusätzlich enthält es eine aktuelle Übersicht über Entwicklungen in der ganzen Welt sowie Fallstudien zu ausgewählten Projekten. Hauptmerkmale: - Ausführliches Referenzwerk zu allen Aspekten der interdisziplinären Fachrichten Wellen- und Gezeitenenergie. - Greift auf die neuesten Forschungsergebnisse und die Erfahrung führender Experten in der numerischen und laborgestützten Modellierung zurück. - Gibt einen Überblick über regionale Entwicklungen in aller Welt, repräsentative Projekte werden in Fallstudien vorgestellt. Wave and Tidal Energy ist ein wertvolles Referenzwerk für eine breite Leserschaft, von Studenten der Ingenieurwissenschaften und technischen Managern über politische Entscheidungsträger bis hin zu Studienabsolventen und Forschern.
Author: Dezhi Ning
Publisher: CRC Press
ISBN: 1000629112
Category : Technology & Engineering
Languages : en
Pages : 384
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Book Description
Wave energy offers a promising renewable energy source, however, technologies converting wave energy into useful electricity face many design challenges. This guide presents numerical modelling and optimization methods for the development of wave energy converter technologies, from principles to applications. It covers the development status and perspectives of wave energy converter systems; the fundamental theories on wave power absorption; the modern wave energy converter concepts including oscillating bodies in single and multiple degree of freedom and oscillating water column technologies; and the relatively hitherto unexplored topic of wave energy harvesting farms. It can be used as a specialist student textbook as well as a reference book for the design of wave energy harvesting systems, across a broad range of disciplines, including renewable energy, marine engineering, infrastructure engineering, hydrodynamics, ocean science, and mechatronics engineering. The Open Access version of this book, available at www.routledge.com has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 license.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
While the field of wave energy has been the subject of numerical simulation, scale model testing, and precommercial project testing for decades, wave energy technologies remain in the early stages of development and must continuing proving themselves as a promising modern renewable energy field. A wave energy converter (WEC) concept, currently being explored, is hoping to add an extra control option to WEC design is the variable-geometry WEC (VGWEC). These VGWECs attempt to incorporate controllable geometric features to adjust the floating body hydrodynamics to favor either power absorption, load shedding, or other operational goals. These variable geometry components have been proposed to be controlled on a sea-state-to-sea-state or wave-to-wave time scale depending on the force (or toque) and bandwidth limitations of the actuators required to manipulate just the controllable geometric hull features. The opportunities of having control over both the WEC geometry components and the power-take-off (PTO) have the potential to improve overall system performance and reliability if a cost-effective solution can be found for a given WEC architecture. This paper will present the recent developments and results of a VGWEC concept that incorporates variable geometry modules into a two-body WEC. In the proposed VGWEC concept, the variable geometry modules consist of air inflatable bags in the surface float and a water inflatable ring in the subsurface body. The surface float is tethered directly to the subsurface body through tether lines each connected to a separate PTO. Adjusting the geometry of both the surface and subsurface bodies along with the PTO coefficients can be shown to maximize power in design sea states while reducing motion response and PTO forces when transitioning to sea states where rated power is reached and load shedding is prioritized in hopes of increasing the sea state operational map.
Author: Stefan Bilbao
Publisher: John Wiley & Sons
ISBN: 0470870184
Category : Science
Languages : en
Pages : 380
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Book Description
Scattering-based numerical methods are increasingly applied to the numerical simulation of distributed time-dependent physical systems. These methods, which possess excellent stability and stability verification properties, have appeared in various guises as the transmission line matrix (TLM) method, multidimensional wave digital (MDWD) filtering and digital waveguide (DWN) methods. This text provides a unified framework for all of these techniques and addresses the question of how they are related to more standard numerical simulation techniques. Covering circuit/scattering models in electromagnetics, transmission line modelling, elastic dynamics, as well as time-varying and nonlinear systems, this book highlights the general applicability of this technique across a variety of disciplines, as well as the inter-relationships between simulation techniques and digital filter design. provides a comprehensive overview of scattering-based numerical integration methods. reviews the basics of classical electrical network theory, wave digital filters, and digital waveguide networks. discusses applications for time-varying and nonlinear systems. includes an extensive bibliography containing over 250 references. Mixing theory and application with numerical simulation results, this book will be suitable for both experts and readers with a limited background in signal processing and numerical techniques.
