Download or read book Steady State and Transient Computational Study of Multiple Hydrokinetic Turbines written by Cosan Daskiran and published by . This book was released on 2016 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: The CFD simulations revealed that the upstream turbine power generation is nearly the same with the single unit power generation for each multiple turbine arrangement. The downstream turbine relative power obtained was 0.18 for the unit placed inline and 0.98 when it was placed outside the wake region. For inline configurations, increasing the stream-wise spacing between the units from 6Dt to 10Dt improved relative power from 0.16 to 0.60, while reducing the rotation speed from 150 rpm to 100 rpm resulted relative power increment from 0.24 to 0.55.

Download or read book Computational Study of Multiple Hydrokinetic Turbine Performance written by Joseph David Jonas and published by . This book was released on 2014 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: The k-omega Shear Stress Transport turbulence model was used to determine the performance of a pair of horizontal-axis hydrokinetic turbines. By varying the separation distance perpendicular to the flow direction between these turbines and computing both power and drag coefficients, the relationship between these outputs and the separation distance as an input was discovered. This study used a rotating reference frame, steady state approximation over three separation distances and two different mesh sizes to verify mesh independence. Once this meshing methodology was verified, two more separation distances were run using the same steady-state approximations at the coarse mesh size to better understand turbine performance at greater separation distances. The results of these simulations show that, at a given separation distance, the left and right turbines have very similar performance. The power and drag coefficients were both found to decrease on the order of 8% as the turbines are brought closer together, which means that, in an infinite and uniform flow field, turbines should be placed as far apart as is feasible to maximize resultant combined power output.

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 Computational Fluid Dynamics Simulations written by Guozhao Ji and published by BoD – Books on Demand. This book was released on 2020-09 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid flows are encountered in our daily life as well as in engineering industries. Identifying the temporal and spatial distribution of fluid dynamic properties is essential in analyzing the processes related to flows. These properties, such as velocity, turbulence, temperature, pressure, and concentration, play important roles in mass transfer, heat transfer, reaction rate, and force analysis. However, obtaining the analytical solution of these fluid property distributions is technically difficult or impossible. With the technique of finite difference methods or finite element methods, attaining numerical solutions from the partial differential equations of mass, momentum, and energy have become achievable. Therefore, computational fluid dynamics (CFD) has emerged and been widely applied in various fields. This book collects the recent studies that have applied the CFD technique in analyzing several representative processes covering mechanical engineering, chemical engineering, environmental engineering, and thermal engineering.

Download or read book Vertical Axis Hydrokinetic Turbines written by Mabrouk Mosbahi; Ahmed and published by . This book was released on 2021-12-14 with total page 150 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 Computational Fluid Dynamic Simulation of Vertical Axis Hydrokinetic Turbines written by Edwin Lenin Chica Arrieta and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrokinetic turbines are one of the technological alternatives to generate and supply electricity for rural communities isolated from the national electrical grid with almost zero emission. These technologies may appear suitable to convert kinetic energy of canal, river, tidal, or ocean water currents into electricity. Nevertheless, they are in an early stage of development; therefore, studying the hydrokinetic system is an active topic of academic research. In order to improve their efficiencies and understand their performance, several works focusing on both experimental and numerical studies have been reported. For the particular case of flow behavior simulation of hydrokinetic turbines with complex geometries, the use of computational fluids dynamics (CFD) nowadays is still suffering from a high computational cost and time; thus, in the first instance, the analysis of the problem is required for defining the computational domain, the mesh characteristics, and the model of turbulence to be used. In this chapter, CFD analysis of a H-Darrieus vertical axis hydrokinetic turbines is carried out for a rated power output of 0.5 kW at a designed water speed of 1.5 m/s, a tip speed ratio of 1.75, a chord length of 0.33 m, a swept area of 0.636 m2, 3 blades, and NACA 0025 hydrofoil profile.

Download or read book Computational Fluid Dynamics Study of a Cross Flow Marine Hydrokinetic Turbine and the Combined Influence of Struts and Helical Blades Preprint written by and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational fluid dynamics study was performed for a cross-flow marine hydro-kinetic turbine. The analysis was done in three dimensions and used the unsteady Reynolds averaged Navier-Stokes solver in the commercial code STAR-CCM+. The base turbine configuration is the RivGen® Turbine, designed by the Ocean Renewable Power Company (ORPC). A convergence and uncertainty analysis was performed for both the spatial and temporal discretization; this was done using the base configuration which features support struts and helical foils. The proposed study aims to compare the impact of the struts on both power performance and blade loading for helical and straight blades.

Download or read book Analysis of a High Solidity Hydrokinetic Turbine Using Computational Fluid Dynamics written by Che-Wei Liu and published by . This book was released on 2012 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transient Analysis of Micro hydrokinetic Turbines for River Applications written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transient Measurement of Heat Transfer in Steady State Turbine Cascades written by Glen Campbell Snedden and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simulating Collisions for Hydrokinetic Turbines written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Performance Evaluation Emulation and Control of Cross flow Hydrokinetic Turbines written by Robert J. Cavagnaro and published by . This book was released on 2016 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross-flow hydrokinetic turbines are a promising option for effectively harvesting energy from fast-flowing streams or currents. This work describes the dynamics of such turbines, analyzes techniques used to scale turbine properties for prototyping, determines and demonstrates the limits of stability for cross-flow rotors, and discusses means and objectives of turbine control. This involves a progression from the analysis of a laboratory-scale prototype turbine to the emulation of a field-scale commercial turbine under realistic control. Understanding of turbine and system component dynamics and performance is leveraged at each phase, with the ultimate goal of enhancing the efficacy of prototype testing and enabling safer, more advanced control techniques. Novel control strategies are under development to utilize low-speed operation (slower than at maximum power point) as a means of shedding power under rated conditions. However, operation in this regime may be unstable. An experiment designed to characterize the stability of a laboratory-scale cross-flow turbine operating near a critically low speed yields evidence that system stall (complete loss of ability to rotate) occurs due, in part, to interactions with turbulent decreases in flow speed. The turbine is capable of maintaining 'stable' operation at critical speed for short duration (typically less than 10 s), as described by exponential decay. The presence of accelerated 'bypass' flow around the rotor and decelerated 'induction' region directly upstream of the rotor, both predicted by linear momentum theory, are observed and quantified with particle image velocimetry (PIV) measurements conducted upstream of the turbine. Additionally, general agreement is seen between PIV inflow measurements and those obtained by an advection-corrected acoustic Doppler velocimeter (ADV) further upstream. Definitive evidence linking observable flow events to the onset of system stall is not found. However, a link between turbulent kinetic energy of the flow, the system time constant, and the turbine's dynamic response to turbulence indicates changes in the flow occurring over a horizon of several seconds create the conditions under which system stall is likely. Performance of a turbine at small (prototype) geometric scale may be prone to undesirable effects due to operation at low Reynolds number and in the presence of high channel blockage. Therefore, testing at larger scale, in open water is desirable. A cross-flow hydrokinetic turbine with a projected area (product of blade span and rotor diameter) of 0.7 m^2 is evaluated in open-water tow trials at three inflow speeds ranging from 1.0 m/s to 2.1 m/s. Measurements of the inflow velocity, the rotor mechanical power, and electrical power output of a complete power take-off (PTO) system are utilized to determine the rotor hydrodynamic efficiency (maximum of 17%) and total system efficiency (maximum of 9%). A lab-based dynamometry method yields individual component and total PTO efficiencies, shown to have high variability and strong influence on total system efficiency. The method of tow-testing is found effective, and when combined with PTO characterization, steady-state performance can be inferred solely from inflow velocity and turbine rotation rate. Dynamic efficiencies of PTO components can effect the overall efficiency of a turbine system, a result from field characterization. Thus, the ability to evaluate such components and their potential effects on turbine performance prior to field deployment is desirable. Before attempting control experiments with actual turbines, hardware-in-the-loop testing on controllable motor-generator sets or electromechanical emulation machines (EEMs) are explored to better understand power take-off response. The emulator control dynamic equations are presented, methods for scaling turbine parameters are developed and evaluated, and experimental results are presented from three EEMs programmed to emulate the same cross-flow turbine. Although hardware platforms and control implementations varied, results show that each EEM is successful in emulating the turbine model at different power levels, thus demonstrating the general feasibility of the approach. However, performance of motor control under torque command, current command, or speed command differed; torque methods required accurate characterization of the motors while speed methods utilized encoder feedback and more accurately tracked turbine dynamics. In a demonstration of an EEM for evaluating a hydrokinetic turbine implementation, a controller is used to track the maximum power-point of the turbine in response to turbulence. Utilizing realistic inflow conditions and control laws, the emulator dynamic speed response is shown to agree well at low frequencies with simulation but to deviate at high frequencies. The efficacy of an electromechanical emulator as an accurate representation of a fielded turbine is evaluated. A commercial horizontally-oriented cross-flow turbine is dynamically emulated on hardware to investigate control strategies and grid integration. A representative inflow time-series with a mean of 2 m/s is generated from high-resolution flow measurements of a riverine site and is used to drive emulation. Power output during emulation under similar input and loading conditions yields agreement with field measurements to within 3% at high power, near-optimal levels. Constant tip-speed ratio and constant speed proportional plus integral control schemes are compared to optimal nonlinear control and constant resistance regulation. All controllers yield similar results in terms of overall system efficiency. The emulated turbine is more responsive to turbulent inflow than the field turbine, as the model utilized to drive emulation does not account for a smoothing effect of turbulent fluctuations over the span of the fielded turbine's rotors. The turbine has a lower inertia than the demand of an isolated grid, indicating a secondary source of power with a similar frequency response is necessary if a single turbine cannot meet the entire demand. Major contributions of this work include exploration of the system time constant as an indicator of turbine dynamic response, evidence a turbine experiences system stall probabilistically, a reduced-complexity field performance characterization methodology, and demonstration of the effectiveness of electromechanical emulators at replicating turbine dynamics.

Download or read book Wind Turbines written by Erich Hau and published by Springer Science & Business Media. This book was released on 2005-12-12 with total page 792 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind Turbines addresses all those professionally involved in research, development, manufacture and operation of wind turbines. It provides a cross-disciplinary overview of modern wind turbine technology and an orientation in the associated technical, economic and environmental fields. It is based on the author's experience gained over decades designing wind energy converters with a major industrial manufacturer and, more recently, in technical consulting and in the planning of large wind park installations, with special attention to economics. The second edition accounts for the emerging concerns over increasing numbers of installed wind turbines. In particular, an important new chapter has been added which deals with offshore wind utilisation. All advanced chapters have been extensively revised and in some cases considerably extended

Download or read book Research Directions in Computational Mechanics written by National Research Council and published by National Academies Press. This book was released on 1991-02-01 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational mechanics is a scientific discipline that marries physics, computers, and mathematics to emulate natural physical phenomena. It is a technology that allows scientists to study and predict the performance of various productsâ€"important for research and development in the industrialized world. This book describes current trends and future research directions in computational mechanics in areas where gaps exist in current knowledge and where major advances are crucial to continued technological developments in the United States.

Download or read book Advances in Thermofluids and Renewable Energy written by Pinakeswar Mahanta and published by Springer Nature. This book was released on 2021-10-21 with total page 681 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises the select proceedings of the International Conference on Recent Trends in Developments of Thermofluids and Renewable Energy (TFRE 2020). The major topics covered include aerodynamics, alternate energy, bio fuel, bio heat transfer, computational fluid dynamics, control mechanism for constant power generation, and energy storage. The book also discusses latest developments in the fields of electric vehicles, hybrid power systems, and solar and renewable energy. Given the scope of its contents, this book will be useful for students, researchers, and professionals interested in the field of thermofluids and renewable energy resources.

Download or read book Wind Turbine Aerodynamics and Vorticity Based Methods written by Emmanuel Branlard and published by Springer. This book was released on 2017-04-05 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book introduces the fundamentals of fluid-mechanics, momentum theories, vortex theories and vortex methods necessary for the study of rotors aerodynamics and wind-turbines aerodynamics in particular. Rotor theories are presented in a great level of details at the beginning of the book. These theories include: the blade element theory, the Kutta-Joukowski theory, the momentum theory and the blade element momentum method. A part of the book is dedicated to the description and implementation of vortex methods. The remaining of the book focuses on the study of wind turbine aerodynamics using vortex-theory analyses or vortex-methods. Examples of vortex-theory applications are: optimal rotor design, tip-loss corrections, yaw-models and dynamic inflow models. Historical derivations and recent extensions of the models are presented. The cylindrical vortex model is another example of a simple analytical vortex model presented in this book. This model leads to the development of different BEM models and it is also used to provide the analytical velocity field upstream of a turbine or a wind farm under aligned or yawed conditions. Different applications of numerical vortex methods are presented. Numerical methods are used for instance to investigate the influence of a wind turbine on the incoming turbulence. Sheared inflows and aero-elastic simulations are investigated using vortex methods for the first time. Many analytical flows are derived in details: vortex rings, vortex cylinders, Hill's vortex, vortex blobs etc. They are used throughout the book to devise simple rotor models or to validate the implementation of numerical methods. Several Matlab programs are provided to ease some of the most complex implementations.