Download or read book Numerical Simulation for Moored Marine Hydrokinetic Turbines written by Basil L. Hacker (Jr.) and published by . This book was released on 2013 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research presented in this thesis utilizes Blade Element Momentum (BEM) theory with a dynamic wake model to customize the OrcaFlex numeric simulation platform in order to allow modeling of moored Ocean Current Turbines (OCTs). This work merges the advanced cable modeling tools available within OrcaFlex with well documented BEM rotor modeling approach creating a combined tool that was not previously available for predicting the performance of moored ocean current turbines. This tool allows ocean current turbine developers to predict and optimize the performance of their devices and mooring systems before deploying these systems at sea. The BEM rotor model was written in C++ to create a back-end tool that is fed continuously updated data on the OCT's orientation and velocities as the simulation is running. The custom designed code was written specifically so that it could operate within the OrcaFlex environment. An approach for numerically modeling the entire OCT system is presented, which accounts for the additional degree of freedom (rotor rotational velocity) that is not accounted for in the OrcaFlex equations of motion. The properties of the numerically modeled OCT were then set to match those of a previously numerically modeled Southeast National Marine Renewable Energy Center (SNMREC) OCT system and comparisons were made. Evaluated conditions include: uniform axial and off axis currents, as well as axial and off axis wave fields. For comparison purposes these conditions were applied to a geodetically fixed rotor, showing nearly identical results for the steady conditions but varied, in most cases still acceptable accuracy, for the wave environment. Finally, this entire moored OCT system was evaluated in a dynamic environment to help quantify the expected behavioral response of SNMREC's turbine under uniform current.

Download or read book Numerical Simulation of a Cross Flow Marine Hydrokinetic Turbine written by Taylor Jessica Hall and published by . This book was released on 2012 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the search for clean, renewable energy, the kinetic energy of water currents in oceans, rivers, and estuaries is being studied as a predictable and environmentally benign source. We investigate the flow past a cross flow hydrokinetic turbine (CFHT) in which a helical blade turns around a shaft perpendicular to the free stream under the hydrodynamic forces exerted by the flow. This type of turbine, while very different from the classical horizontal axis turbine commonly used in the wind energy field, presents advantages in the context of hydrokinetic energy harvesting, such as independence from current direction, including reversibility, stacking, and self-starting without complex pitch mechanisms. This thesis develops a numerical simulation methodology that applies the Reynolds Average Navier Stokes equations and the three-dimensional sliding mesh technique to model CFHTs. The methodology is validated against small scale experiments, available within NNMREC at the University of Washington and is used to investigate the efficiency of the energy capture and the hydrodynamic forces acting on the blades. First, we study the stationary turbine and conclude that the developed methodology accurately models the starting torque of a turbine initially in static conditions; some limitations are found, however, in predicting separated flow. The dynamic performance of the rotating turbine is predicted with reasonable accuracy using the sliding mesh technique. Excellent qualitative agreement with experimental trends is found in the results, and the actual predicted values from the simulations show good agreement with measurements. Though limitations in accurately modeling dynamic stall for the rotating turbine are confirmed, the good qualitative agreement suggests this methodology can be used to support turbine design and performance over a wide range of parameters, minimizing the number of prototypes to build and experiments to run in the pursuit of an optimized turbine. This methodology can also provide a cost-effective way of evaluating detailed full scale effects, such as mooring lines or local bottom bathymetry features, on both turbine performance and environmental assessment.

Download or read book Numerical Investigation of Marine Hydrokinetic Turbines written by Amir Teymour Javaherchi Mozafari and published by . This book was released on 2014 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: A hierarchy of numerical models, Single Rotating Reference Frame (SRF) and Blade Element Model (BEM), were used for numerical investigation of horizontal axis Marine Hydrokinetic (MHK) Turbines. In the initial stage the SRF and BEM were used to simulate the performance and turbulent wake of a flume- and a full-scale MHK turbine reference model. A significant level of understanding and confidence was developed in the implementation of numerical models for simulation of a MHK turbine. This was achieved by simulation of the flume-scale turbine experiments and comparison between numerical and experimental results. Then the developed numerical methodology was applied to simulate the performance and wake of the full-scale MHK reference model (DOE Reference Model 1). In the second stage the BEM was used to simulate the experimental study of two different MHK turbine array configurations (i.e. two and three coaxial turbines). After developing a numerical methodology using the experimental comparison to simulate the flow field of a turbine array, this methodology was applied toward array optimization study of a full-scale model with the goal of proposing an optimized MHK turbine configuration with minimal computational cost and time. In the last stage the BEM was used to investigate one of the potential environmental effects of MHK turbine. A general methodological approach was developed and experimentally validated to investigate the effect of MHK turbine wake on the sedimentation process of suspended particles in a tidal channel.

Download or read book Numerical Simulation of Admiralty Inlet WA with Tidal Hydrokinetic Turbine Siting Application written by Kristen M. Thyng and published by . This book was released on 2012 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tidal hydrokinetic energy has been recognized as a potential source of sustainable, renewable energy. In order to properly site turbines for commercial-scale development, the complex flow conditions in a potential deployment region must be understood. Viable locations for turbines are limited by many factors, including underwater space that is above the bottom boundary layer, below shipping traffic, within areas of strong currents, and yet avoids additional fatiguing stresses. The primary area of interest in the Puget Sound for commercial tidal energy development is Admiralty Inlet, which includes potentially disruptive flow features such as vortices and strong turbulence. This dissertation seeks to increase the body of knowledge of these features both from an oceanographic perspective and as they pertain to turbine site characterization. The primary means of studying Admiralty Inlet in this document is through numerical simulation of the region using the Regional Ocean Modeling System (ROMS). The model output is found to compare well with field data, capturing eddy fields, turbulence properties, relative tidal phases, and illuminating many flow features. Horizontal velocities in the simulation are, on average, approximately 75% the size of those found in the data. This speed deficiency is inherited from the forcing model in which the Admiralty Inlet simulation is nested. The model output also shows that the flow field of this fjord-like estuary is largely affected by a headland on the northeast side of the Inlet. Vortices generated by this headland, Admiralty Head, are found to vary considerably depending on the tidal cycle. The eddies can persist beyond the half-cycle of generation to significantly affect the horizontal speed and other flow field properties in the subsequent half-cycle. Detailed analysis of the vertical vorticity governing equation shows that advection, tilting, stretching, and boundary generation are the most significant processes dictating the behavior of the vorticity. Turbulence modeling in the simulation is carried out via a k- & epsilon turbulence closure scheme. Comparisons of model output with high resolution field data show the model to perform reasonably well: predicted Reynolds stress and turbulent dissipation rate values are usually within a factor of two of the field data. The turbulent kinetic energy from the simulation compares well with field data that is restricted to the frequency range of classical turbulence. The energy density spectrum of the data is found to follow Kolmogorov's theory beyond the inertial subrange. Using this fact and Taylor's frozen field approximation, an inferred calculation for the turbulent kinetic energy is derived that spans the full frequency range of the data set. The output from the inferred calculation compares well with the full turbulent kinetic energy from the field data. Maps of metrics for tidal turbine siting are generated that address many considerations for turbine placement, and can be adjusted for the model's speed deficiency with a simple multiplication factor. Among the possible best locations for turbine deployment are north of Point Wilson on the west side of Admiralty Inlet and near the center of the channel between Point Wilson and Admiralty Head. These locations have a strong tidal resource available along with highly bi-directional tidal currents and low turbulence levels.

Download or read book Numerical Modeling of the Effects of a Free Surface on the Operating Characteristics of Marine Hydrokinetic Turbines written by Samantha Jane Adamski and published by . This book was released on 2013 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Marine Hydrokinetic (MHK) turbines are a growing area of research in the renewable energy field because tidal currents are a highly predictable clean energy source. The presence of a free surface may influence the flow around the turbine and in the wake, critically affecting turbine performance and environmental effects through modification of the wake physical variables. The characteristic Froude number that control these processes is still a matter of controversy, with the channel depth, the turbine's hub depth, the blade tip depth and the turbine diameter as potential candidates for a length scale. We use a Reynolds Averaged Navier Stokes (RANS) simulation with a Blade Element Theory (BET) model of the turbine and with a Volume of Fluid model, which is used to track the free surface dynamics, to understand the physics of the wake-free surface interactions. Pressure and flow rate boundary conditions for a channel's inlet, outlet and air side have been tested in an effort to determine the optimum set of simulation conditions for MHK turbines in rivers or shallow estuaries. Stability and accuracy in terms of power extraction and kinetic and potential energy budgets are considered. The goal of this research is to determine, quantitatively in non-dimensional parameter space, the limit between negligible and significant free surface effects on MHK turbine analysis.

Download or read book Advances In Numerical Simulation Of Nonlinear Water Waves written by Qingwei Ma and published by World Scientific. This book was released on 2010-04-15 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of the Earth's surface is covered by water. Many aspects of our everyday lives and activities may be affected by water waves in some way. Sometimes, the waves can cause disaster. One of the examples was the tsunami that occurred in the Indian Ocean on 26 December 2004. This indicates how important it is for us to fully understand water waves, in particular the very large ones. One way to do so is to perform numerical simulation based on the nonlinear theory. Considerable research advances have been made in this area over the past decade by developing various numerical methods and applying them to emerging problems; however, until now there has been no comprehensive book to reflect these advances. This unique volume aims to bridge this gap.This book contains 18 self-contained chapters written by more than 50 authors from 12 different countries, many of whom are world-leading experts in the field. Each chapter is based mainly on the pioneering work of the authors and their research teams over the past decades. The chapters altogether deal with almost all numerical methods that have been employed so far to simulate nonlinear water waves and cover many important and very interesting applications, such as overturning waves, breaking waves, waves generated by landslides, freak waves, solitary waves, tsunamis, sloshing waves, interaction of extreme waves with beaches, interaction with fixed structures, and interaction with free-response floating structures. Therefore, this book provides a comprehensive overview of the state-of-the-art research and key achievements in numerical modeling of nonlinear water waves, and serves as a unique reference for postgraduates, researchers and senior engineers working in industry.

Download or read book Numerical Analysis of an Axial Flow Horizontal Axis Marine Hydrokinetic Turbine written by Aarshana Parekh and published by . This book was released on 2019 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tidal energy extraction using marine hydrokinetic devices has become an important area of research in the renewable energy field in recent years because of the highly predictable nature of the tides. Due to its early stage of development, many studies need yet to be done before deployment of these devices at tidal sites. It is essential to have a thorough understanding of the turbine performance and wake properties before determining the array arrangement for tidal farms. In this thesis, flow behavior in the wake of a counter-rotating dual rotor horizontal axis tidal turbine is studied by numerically solving the Reynolds Averaged Navier Stokes (RANS) Equations. The rotational effects of the turbine are modeled using the sliding mesh technique. The realizable k-epsilon model is employed to solve the closure problem. The methodology is validated against experimental data measured in open channel tests conducted at the St. Anthony Falls Laboratory of the University of Minnesota, in collaboration with Sandia National Laboratory, to investigate the turbine efficiency and the physical dynamics of the wake. The transient performance of the turbine is predicted with good accuracy using the sliding mesh model, with some level of disagreement found in predicting the velocity deficit in the flow. The limitations of accurately predicting the turbulent flow properties for the turbine are addressed and the sliding mesh technique is proven to capture effectively the different coherent structures in the wake. The qualitative agreement of the method suggests that this model can be used to explore turbine design and wake characteristics over various parameters in a cost-effective manner. This method can also provide critical parameters needed for designing efficient tidal farms.

Download or read book Multiscale Analysis of Flows Past Marine Hydrokinetic Devices Using Numerical Simulations written by Karina A. Soto Rivas and published by . This book was released on 2021 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Water Waves written by Jianhua Tao and published by Springer Nature. This book was released on 2020-03-30 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the numerical simulation of water waves, which combines mathematical theories and modern techniques of numerical simulation to solve the problems associated with waves in coastal, ocean, and environmental engineering. Bridging the gap between practical mathematics and engineering, the book describes wave mechanics, establishment of mathematical wave models, modern numerical simulation techniques, and applications of numerical models in engineering. It also explores environmental issues related to water waves in coastal regions, such as pollutant and sediment transport, and introduces numerical wave flumes and wave basins. The material is self-contained, with numerous illustrations and tables, and most of the mathematical and engineering concepts are presented or derived in the text. The book is intended for researchers, graduate students and engineers in the fields of hydraulic, coastal, ocean and environmental engineering with a background in fluid mechanics and numerical simulation methods.

Download or read book Vertical Axis Hydrokinetic Turbines Numerical and Experimental Analyses written by Mabrouk Mosbahi and published by Bentham Science Publishers. This book was released on 2021-12-14 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook is a guide to numerical and experimental processes that are used to analyze and improve the efficiency of vertical axis rotors. Chapters present information that is required to optimize the geometrical parameters of rotors or understand how to augment upstream water velocity. The authors of this volume present a numerical model to characterize the water flow around the vertical axis rotors using commercial CFD code in Ansys Fluent®. The software has been used to select adequate parameters and perform computational simulations of spiral Darrieus turbines. The contents of the volume explain the experimental procedure carried out to evaluate the performance of the spiral Darrieus turbine, how to characterize the water flow in the vicinity of the tested turbine and the method to assess the spiral angle influence on the turbine performance parameters. Results for different spiral angles (ranging from 10° to 40°) are presented. This volume is a useful handbook for engineers involved in power plant design and renewable energy sectors who are studying the computational fluid dynamics of vertical axis turbines (such as Darrieus turbines) that are used in hydropower projects. Key features: - 4 chapters that cover the numerical and experimental analysis of vertical axis rotors and hydrokinetic turbines - Simple structured layout for easy reading (methodology, models and results) - Bibliographic study to introduce the reader to the subject - A wide range of parameters included in experiments - A comprehensive appendix of tables for mechanical parameters, statistical models, rotor parameters and geometric details.

Download or read book Modeling and Optimizing Hydrokinetic Turbine Arrays Using Numerical Simulations written by Olivier Gauvin Tremblay and published by . This book was released on 2021 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to plan a river hydrokinetic turbine array deployment and to maximize its energy extraction, turbine array simulations are often carried out. However, in a context where tens of turbines are deployed, it is unthinkable to simulate the complete rotating geometry of every turbine. It is therefore necessary to use simplified models that reproduce accurately the turbines and that incorporate all the main interactions taking place in a turbine array, namely the turbine-wake interactions, the blockage effects and the interaction with the resource. The Effective Performance Turbine Model (EPTM) is a suitable tool in that sense, allowing to test and analyze a large amount of different array configurations at a low computational cost. Although the EPTM has been developed to serve as a tool for array analysis, it has only been tested up to now in a uniform flow with a low turbulence level. For this reason, the EPTM has been validated and adapted in this work to ensure a proper and reliable use in river array flow conditions. Herein, the efforts has been mainly put on a cross-flow turbine (CFT) technology. First, a numerical methodology has been developed to reproduce river flow conditions and array flow conditions, which include shear, large-scale temporal fluctuations and (modeled) turbulence. Following 3D blade-resolved turbine simulations, it is found that a turbine operating in those conditions sees a reduction of its performance, especially when the shear aspect is present. However, it turns out that the effective drag coefficient remains essentially unchanged, allowing to use the same local effective force coefficient distribution in every situation. Moreover, although the effective power coefficient appears to be lower than for a turbine in idealized flow conditions, it does not vary depending of the type of perturbation and its decrease is small under free-surface conditions. This is important for the use of the EPTM, since the simplified model is based on this assumption. Multiple comparisons between EPTM and blade-resolved turbine simulations in river/array flow conditions have confirmed that the EPTM-CFT is always able to predict accurately the performances of the turbines and to reproduce their mean wake with a high degree of reliability. Following this validation procedure, a series of turbine array simulations have been conducted using the EPTM-CFT. Assuming a turbulent flow environment, many vertical-axis turbine array configurations have been tested to study more precisely the effect of local blockage, lateral and longitudinal spacing, array staggering and direction of rotation on turbine performance. Results have shown that all aspects of blockage, local and global, must be considered simultaneously with the possibility of turbine-wake interaction, especially when the turbines generate a wake that deflects sideways down-stream. The latter aspect could play an important role in determining whether or not the array should be staggered. For a multiple-row array, this aspect also affects the relevance of the different array parameters used. Indeed, in this context, the lateral spacing becomes more meaningful than the local blockage value. To help decide on the optimal lateral and longitudinal spacing to set within an array, a new parameter has been proposed: the marginal power per turbine. As many economic variables can come into play, this parameter helps quantifying the benefit of adding rows or columns of turbines in comparison to the already installed power. Finally, it is possible, for an identified optimal turbine array, to assess its impact on the resource. Based on an actual river site, a realistic simulation of a turbine array in river has been performed using the methodology previously developed. The simulation results, compared with the results of more simplified simulations, have pointed out that an appropriate channel geometry and an accurate inflow velocity distribution are essential to obtain reliable array performances. Although it arises that taking into account the free surface has negligibly affected the array performances and the water level upstream for the case considered, it remains that the assessment of the impact on the resource is always relevant since the rise in the water level can be larger if the blockage ratio or the Froude number are higher.

Download or read book Marine Renewable Energy written by Zhaoqing Yang and published by Springer. This book was released on 2017-04-24 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: This complete reference to marine renewable energy covers aspects of resource characterization and physical effects of harvesting the ocean’s vast and powerful resources—from wave and tidal stream to ocean current energy. Experts in each of these areas contribute their insights to provide a cohesive overview of the marine renewable energy spectrum based on theoretical, numerical modeling, and field-measurement approaches. They provide clear explanations of the underlying physics and mechanics, and give close consideration to practical implementation aspects, including impacts on the physical system. Engineers, researchers, and students alike will find invaluable tools and studies that will aid them in realizing significant sustainable energy production from near-shore and ocean environments.

Download or read book A Numerical Investigation Into the Effects of Positioning and Rotation on the Performance of Two Vertical axis Hydrokinetic Turbines written by Jody Soviak and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical simulation allows investigation into the influence of separation distance and rotation on the performance of two vertical-axis hydrokinetic turbines. Compu- tational fluid dynamics is applied to calulate the lift and drag coefficients acting upon interacting NACA 0021 turbine blades for a Reynolds number of Red = 10, 000. To understand the effect of separation distance, large-eddy simulation of the flow around side-by-side and staggered cylinders, ReD = 3,000, and airfoils, Rec = 3,000, are also performed. Based upon the simulations, a drag reduction of 11.3% and 19.8% is determined for the downstream cylinder and airfoil, respectively. A reduction in Reynolds stresses is also observed for the staggered configuration compared to the side-by-side configuration. Due to computational resources of large-eddy simulation, the Reynolds averaged Navier-Stokes method is also applied to investigate the influence of separation distance and rotation on two vertical axis hydrokinetic turbines. The numerical simulations show that a drag reduction of 15.5% occurs when the non-dimensional spanwise and streamwise separation distances, based on turbine diameter, reach 1 and 2, respectively.

Download or read book Fluid structure Interaction written by Cedric Leblond and published by John Wiley & Sons. This book was released on 2022-11-30 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the numerical simulation of fluid–structure interaction (FSI) for application in marine engineering. Fluid–Structure Interaction details a wide range of modeling methods (numerical, semi-analytical, empirical), calculation methods (finite element, boundary element, finite volume, lattice Boltzmann method) and numerical approaches (reduced order models and coupling strategy, among others). Written by a group of experts and researchers from the naval sector, this book is intended for those involved in research or design who are looking to gain an overall picture of hydrodynamics, seakeeping and performance under extreme loads, noise and vibration. Using a concise, didactic approach, the book describes the ways in which numerical simulation contributes to modeling and understanding fluid–structure interaction for designing and optimizing the ships of the future.

Download or read book Renewable Energy in Marine Environment written by Eugen Rusu and published by MDPI. This book was released on 2020-03-25 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of human-caused global warming are obvious, requiring new strategies and approaches. The concept of business-as-usual is now no longer beneficial. Extraction of renewable energy in marine environments represents a viable solution and an important path for the future. These huge renewable energy resources in seas and oceans can be harvested, including wind, tide, and waves. Despite the initial difficulties related mostly to the elevated operational risks in the harsh marine environment, newly developed technologies are economically effective or promising. Simultaneously, many challenges remain to be faced. These are the main issues targeted by the present book, which is associated with the Special Issue of Energies Journal entitled “Renewable Energy in Marine Environment”. Papers on innovative technical developments, reviews, case studies, and analytics, as well as assessments, and papers from different disciplines that are relevant to the topic are included. From this perspective, we hope that the results presented are of interest to for scientists and those in related fields such as energy and marine environments, as well as for a wider audience.

Download or read book The Mathematics of Marine Modelling written by Henk Schuttelaars and published by Springer Nature. This book was released on 2022-11-30 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past few decades, numerical simulation has become instrumental in understanding the dynamics of seas, coastal regions and estuaries. The decision makers rely more and more frequently on model results for the management of these regions. Some modellers are insufficiently aware of the theoretical underpinning of the simulation tools they are using. On the other hand, a number of applied mathematicians tend to view marine sciences as a domain in which they would like to use the tools they have a good command of. Bridging the gap between model users and applied mathematicians is the main objective of the present book. In this respect a vast number of issues in which mathematics plays a crucial role will be addressed.

Download or read book An Evaluation of the U S Department of Energy s Marine and Hydrokinetic Resource Assessments written by National Research Council and published by National Academies Press. This book was released on 2013-04-23 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing renewable energy development, both within the United States and abroad, has rekindled interest in the potential for marine and hydrokinetic (MHK) resources to contribute to electricity generation. These resources derive from ocean tides, waves, and currents; temperature gradients in the ocean; and free-flowing rivers and streams. One measure of the interest in the possible use of these resources for electricity generation is the increasing number of permits that have been filed with the Federal Energy Regulatory Commission (FERC). As of December 2012, FERC had issued 4 licenses and 84 preliminary permits, up from virtually zero a decade ago. However, most of these permits are for developments along the Mississippi River, and the actual benefit realized from all MHK resources is extremely small. The first U.S. commercial gridconnected project, a tidal project in Maine with a capacity of less than 1 megawatt (MW), is currently delivering a fraction of that power to the grid and is due to be fully installed in 2013. As part of its assessment of MHK resources, DOE asked the National Research Council (NRC) to provide detailed evaluations. In response, the NRC formed the Committee on Marine Hydrokinetic Energy Technology Assessment. As directed in its statement of task (SOT), the committee first developed an interim report, released in June 2011, which focused on the wave and tidal resource assessments (Appendix B). The current report contains the committee's evaluation of all five of the DOE resource categories as well as the committee's comments on the overall MHK resource assessment process. This summary focuses on the committee's overarching findings and conclusions regarding a conceptual framework for developing the resource assessments, the aggregation of results into a single number, and the consistency across and coordination between the individual resource assessments. Critiques of the individual resource assessment, further discussion of the practical MHK resource base, and overarching conclusions and recommendations are explained in An Evaluation of the U.S. Department of Energy's Marine and Hydrokinetic Resource Assessment.