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 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 Effect of Flow and Fluid Structures on the Performance of Vertical River Hydrokinetic Turbines written by Amir Hossein Birjandi 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 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 Journal of Scientific and Industrial Research written by and published by . This book was released on 2013 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Advances of Science and Technology written by Mulatu Liyew Berihun and published by Springer Nature. This book was released on 2022-01-01 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: This two-volume set of LNICST 411 and 412 constitutes the refereed post-conference proceedings of the 9th International Conference on Advancement of Science and Technology, ICAST 2021, which took place in August 2021. Due to COVID-19 pandemic the conference was held virtually. The 80 revised full papers were carefully reviewed and selected from 202 submissions. The papers present economic and technologic developments in modern societies in 7 tracks: Chemical, Food and Bioprocess Engineering; Electrical and Electronics Engineering; ICT, Software and Hardware Engineering; Civil, Water Resources, and Environmental Engineering ICT; Mechanical and Industrial Engineering; Material Science and Engineering; Energy Science, Engineering and Policy.

Download or read book A Numerical Investigation Into Torque Ripple and Power in Vertical Axis Tidal Turbines written by Jonathan Douglas Logie Winchester and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design and Critical Performance Evaluation of Horizontal Axis Hydrokinetic Turbines written by Suchi Subhra Mukherji and published by . This book was released on 2010 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The current work discusses the hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkT) under different turbine geometries and flow conditions. Hydrokinetic turbines are a class of zero-head hydropower systems which utilize kinetic energy of flowing water to drive a generator. However, such turbines often suffer from low-efficiency. A detailed computational fluid dynamics study was performed using a low-order k-[omega] SST (Shear Stress Transport) turbulence model to examine the effect of each of tip-speed ratio, solidity, angle of attack and number of blades on the performance of small HAHkTs with a power capacity of 10 kW. The numerical models (both two-dimensional and three-dimensional) developed for these purposes were validated with blade element momentum theory. The two-dimensional numerical models suggest an optimum angle of attack that maximizes lift as well as lift to drag ratio thereby yielding the maximum power output. In addition, our three-dimensional model is used to estimate optimum turbine solidity and blade numbers that produces maximum power coefficient at a given tip speed ratio. Furthermore, the axial velocity deficit downstream of the turbine rotor provides quantitative details of energy loss suffered by each turbine at ambient flow conditions. The velocity distribution provides confirmation of the stall-delay phenomenon that occurs due to the rotation of the turbine. In addition, it provides further verification of optimum tip speed ratio corresponding to maximum power coefficient obtained from the solidity analysis"--Abstract, leaf iii.

Download or read book Effect of Shroud on the Performance of Horizontal Axis Hydrokinetic Turbines written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Investigation and Performance Characteristic Mapping of an Archimedean Screw Hydroturbine written by W. Chris Schleicher and published by . This book was released on 2012 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational Fluid Dynamics (CFD) is a crucial tool in the design and analysis of hydraulic machinery, especially in the design of a micro hydro turbine. The micro hydro turbine in question is for a low head (less than 60 meters), low volumetric flow rate (0.005 m3/s to 0.5 m 3/s) application with rotation rates varying from 200 RPM to 1500 RPM. The design of the runner geometry is discussed, specifically a non-uniform Archimedean Spiral with an outer diameter of 6 inches and length of 19.5 inches. The transient simulation method, making use of a frame of reference change and a rotating mesh between time-steps, is explained as well as the corresponding boundary conditions. Both simulation methods are compared and are determined to produce similar results. The rotating frame of reference method was determined to be the most suitable method for the mapping of performance characteristic such as required head, torque, power, and efficiency. Results of simulations for a non-uniform Archimedean Spiral are then presented. First, a spectral and temporal convergence study is conducted to make sure that the results are independent of time-step and mesh selection. Performance characteristics of a non-uniform pitched blade turbine are determined for a wide range of volumetric flow rates and rotation rates. The maximum efficiency of the turbine is calculated around 72% for the design of the turbine blade considered in the present study.

Download or read book Performance Evaluation of Coaxial Horizontal Axis Hydrokinetic Turbines System written by Abdulaziz Mohammed Abutunis and published by . This book was released on 2014 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Hydrokinetic energy technologies are emerging as a viable solution for renewable power generation. Unlike conventional hydropower turbines, hydrokinetic turbines are environmentally friendly; they operate at zero-head, and do not need dams to preserve the water. Unfortunately, they have a low efficiency which makes their design a challenging task. This work was focused on the hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkTs) under different turbine arrangements and flow conditions. It was undertaken in an effort to improve the efficiency of small HAHkTs that harness a river’s kinetic energy. Four sets of experiments were performed in a water tunnel to investigate small-scale constant cross-section HAHkT models with various configurations. The first set of experiments provided insight into the operating characteristics of a 3-blade single turbine by varying its pitch angle ([theta]) , tip speed ratio (TSR), flow speed (U[sub infinity]), and applied load. A multi-turbine system of both two and three 3- blade rotors (mounted coaxially to the same shaft) was tested in the second set of experiments. The purpose was to decrease the turbine system solidity while increasing the blade number. Here, the number of and the distance between rotors as well as the rotors relative installation angle were investigated. A long duct reducer was used to shroud single turbine and multi- turbine system in the third set of experiments. The particle image velocimetry (PIV) technique was used in the final set of experiments to examine the flow patterns at different axial locations downstream from two different turbine configurations. The effect of the flow speed on the wake characteristics was also examined in this experiment"--Abstract, page iii.

Download or read book Development of Horizontal Axis Hydrokinetic Turbine Using Experimental and Numerical Approaches written by Abdulaziz Mohammed Abutunis and published by . This book was released on 2020 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Hydrokinetic energy conversion systems (HECSs) are emerging as viable solutions for harnessing the kinetic energy in river streams and tidal currents due to their low operating head and flexible mobility. This study is focused on the experimental and numerical aspects of developing an axial HECS for applications with low head ranges and limited operational space. In Part I, blade element momentum (BEM) and neural network (NN) models were developed and coupled to overcome the BEM's inherent convergence issues which hinder the blade design process. The NNs were also used as a multivariate interpolation tool to estimate the blade hydrodynamic characteristics required by the BEM model. The BEM-NN model was able to operate without convergence problems and provide accurate results even at high tip speed ratios. In Part II, an experimental setup was developed and tested in a water tunnel. The effects of flow velocity, pitch angle, number of blades, number of rotors, and duct reducer were investigated. The performance was improved as rotors were added to the system. However, as rotors added, their contribution was less. Significant performance improvement was observed after incorporating a duct reducer. In Part III, a computational fluid dynamics (CFD) simulation was conducted to derive the optimum design criteria for the multi-turbine system. Solidity, blockage, and their interactive effects were studied. The system configuration was altered, then its performance and flow characteristics were investigated. The experimental setup was upgraded to allow for blockage correction. Particle image velocimetry was used to investigate the wake velocity profiles and validate the CFD model. The flow characteristics and their effects on the turbines performance were analyzed"--Abstract, page iv.

Download or read book Impact of Macro turbulent Structures from Mooring Anchors and Rough Riverbeds on the Performance of a Horizontal Axis Hydrokinetic Turbine written by Sixtus Ekezie and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reported are laboratory and field measurements obtained to characterize the flow structures caused by mooring anchors and rough river beds on the performance of hydrokinetic turbines. Series of flow velocity profile in-situ measurements characterize the energetic flow at the Canadian Hydrokinetic Turbine Test Centre (CHTTC) located on the Winnipeg River. Using an acoustic Doppler velocimeter, a novel method was applied to obtain the flow velocity through the water column to contribute to the design and optimization of power production from a hydrokinetic turbine. The acoustic Doppler velocimeter measures the mean and fluctuating velocity components at a frequency of 64 Hz. Tests were performed between 2.1 and 2.7 m/s upstream and downstream of turbine mooring anchors. Anchors occupy 12% of the water column height. Near-surface measurements show a 9.9% increase in turbulence intensity and 8.8% increase in free-stream velocity due to the upstream turbine mooring structures while the profile measurements show a temporal variation in the velocity and turbulence intensity profiles. In a more detailed laboratory investigation, four different scaled geometries of turbine mooring anchors were designed, fabricated and tested, including a 19.8 cm diameter horizontal axis turbine in a water tunnel. Tests are first performed at a steady velocity of 1.1 m/s and at an unobstructed Reynolds number of 217000 based on rotor diameter. During this testing, velocity measurements were taken at different locations upstream of a scaled horizontal turbine to determine the optimum operating conditions in a steady free-stream velocity. Furthermore, 25 surface roughness and four mooring anchor geometries were tested and located 2 and 3 rotor diameter upstream of the turbine in the water tunnel. Results show a 14% to 36% increase in turbine performance due to the impact of mooring anchor geometries and surface roughness. These results are useful in choosing a turbine mooring anchor design, geometry, and location to enhance turbine performance and obtain an understanding of a rough riverbed at the energetic river site.

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.