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Conducting Large Eddy Simulation To Explore The Impact Of Different Forest Scenarios On Wind Turbine Wake Flow Under Varying Ground Roughness
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Book Synopsis Conducting Large Eddy Simulation to Explore the Impact of Different Forest Scenarios on Wind Turbine Wake Flow Under Varying Ground Roughness by :
Download or read book Conducting Large Eddy Simulation to Explore the Impact of Different Forest Scenarios on Wind Turbine Wake Flow Under Varying Ground Roughness written by and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Large Eddy Simulations of Floating Offshore Wind Turbine Wakes with Coupled Platform Motion: Preprint by :
Download or read book Large Eddy Simulations of Floating Offshore Wind Turbine Wakes with Coupled Platform Motion: Preprint written by and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The growing prospect for large farms of floating offshore wind turbines requires a better understanding of wake effects for floating turbines, particularly the differences when compared to fixed-bottom turbine wakes. The increased range of motion of floating platforms can influence wake characteristics, affecting downstream turbines. In this work, large eddy simulations with an actuator line model are used to study downstream wake characteristics of the NREL 5-MW reference turbine mounted on the OC3-UMaine spar platform for several different metocean conditions. The simulations are carried out in the Simulator fOr Wind Farm Applications coupled with OpenFAST for the platform and turbine motion. The downstream wake characteristics of the floating platform are compared to equivalent fixed-bottom cases for different wind speeds, wave heights, wind-wave alignments, and turbine yaw angles. Overall, the differences in wake shape between floating and fixed platforms are associated with mean platform displacements, while differences in turbulence are associated with time-varying platform motion. However, these observed wake differences between fixed and floating platforms are small, especially for higher wind speeds and lower wave heights.
Book Synopsis Investigating Wind Turbine Impacts on Near-wake Flow Using Profiling Lidar Data and Large-eddy Simulations with an Actuator Disk Model by :
Download or read book Investigating Wind Turbine Impacts on Near-wake Flow Using Profiling Lidar Data and Large-eddy Simulations with an Actuator Disk Model written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, wind turbine impacts on the atmospheric flow are investigated using data from the Crop Wind Energy Experiment (CWEX-11) and large-eddy simulations (LESs) utilizing a generalized actuator disk (GAD) wind turbine model. CWEX-11 employed velocity-azimuth display (VAD) data from two Doppler lidar systems to sample vertical profiles of flow parameters across the rotor depth both upstream and in the wake of an operating 1.5 MW wind turbine. Lidar and surface observations obtained during four days of July 2011 are analyzed to characterize the turbine impacts on wind speed and flow variability, and to examine the sensitivity of these changes to atmospheric stability. Significant velocity deficits (VD) are observed at the downstream location during both convective and stable portions of four diurnal cycles, with large, sustained deficits occurring during stable conditions. Variances of the streamwise velocity component, [sigma]u, likewise show large increases downstream during both stable and unstable conditions, with stable conditions supporting sustained small increases of [sigma]u, while convective conditions featured both larger magnitudes and increased variability, due to the large coherent structures in the background flow. Two representative case studies, one stable and one convective, are simulated using LES with a GAD model at 6 m resolution to evaluate the compatibility of the simulation framework with validation using vertically profiling lidar data in the near wake region. Virtual lidars were employed to sample the simulated flow field in a manner consistent with the VAD technique. Simulations reasonably reproduced aggregated wake VD characteristics, albeit with smaller magnitudes than observed, while [sigma]u values in the wake are more significantly underestimated. The results illuminate the limitations of using a GAD in combination with coarse model resolution in the simulation of near wake physics, and validation thereof using VAD data.
Book Synopsis Large-Eddy Simulation of Wind Turbine Blade and Wake Flow by : Xu Huang
Download or read book Large-Eddy Simulation of Wind Turbine Blade and Wake Flow written by Xu Huang and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Large Eddy Simulation Study of the Effect of Large Wind Farms on Humidity by : Oumnia El Fajri
Download or read book Large Eddy Simulation Study of the Effect of Large Wind Farms on Humidity written by Oumnia El Fajri and published by . This book was released on 2016 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric boundary layer flows around wind turbines distributed in a large wind farm can be examined by the use of large eddy simulation (LES), which is based on the assumption that large eddies in the flow are anisotropic and depend on the mean flow and the configuration geometry, while smaller eddies are isotropic and homogeneous, and can be modeled via subgrid scale models. In this thesis, a pseudo-spectral LES code with inflow conditions imposed through a precursor concurrent simulation is utilized to model the flow around a single wind turbine or a large wind farm operating in thermallystratified conditions. The effect of the wind turbines on humidity is monitored through an additional scalar convection equation. It is found that on average, the effect of an individual wind turbine on the humidity is less than 1%, while the effect of the wind farm on humidity can reach 1-2% in the cumulative wakes.
Download or read book Coalescing Wind Turbine Wakes written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A team of researchers from the National Renewable Energy Laboratory and Statoil used large-eddy simulations to numerically investigate the merging wakes from upstream offshore wind turbines. Merging wakes are typical phenomena in wind farm flows in which neighboring turbine wakes consolidate to form complex flow patterns that are as yet not well understood. In the present study, three 6-MW turbines in a row were subjected to a neutrally stable atmospheric boundary layer flow. As a result, the wake from the farthest upstream turbine conjoined the downstream wake, which significantly altered the subsequent velocity deficit structures, turbulence intensity, and the global meandering behavior. The complexity increased even more when the combined wakes from the two upstream turbines mixed with the wake generated by the last turbine, thereby forming a "triplet" structure. Although the influence of the wake generated by the first turbine decayed with downstream distance, the mutated wakes from the second turbine continued to influence the downstream wake. Two mirror-image angles of wind directions that yielded partial wakes impinging on the downstream turbines yielded asymmetric wake profiles that could be attributed to the changing flow directions in the rotor plane induced by the Coriolis force. In conclusion, the turbine wakes persisted for extended distances in the present study, which is a result of low aerodynamic surface roughness typically found in offshore conditions.
Book Synopsis Large Eddy Simulations of Canopy Flows Over Complex Terrain by : Yulong Ma
Download or read book Large Eddy Simulations of Canopy Flows Over Complex Terrain written by Yulong Ma and published by . This book was released on 2019 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Forest canopies cover about 30% of the land surfaces some of which are hilly or mountainous. Both complex terrain and forest canopies influence mean flow and turbulence, playing a critical role in affecting momentum and scalar transfer. Although recent advances have been made in numerical simulations of canopy flows, few have been conducted over steep slope terrain and considered full sets of physical and physiological processes in sub-canopy layers, which greatly limits our understanding of canopy flows and scalar transfer. To address this limitation, we upgrade the Weather Research and Forecasting model with the large-eddy simulations module (WRF-LES) by incorporating the immersed-boundary method (IBM) to improve the simulations over steep slope terrain. In addition, an advanced multiple layer canopy module (MCANOPY) is developed based largely on the Community Land Model version 4.5 and coupled with WRF-LES to simulate sources and/or sinks of momentum, heat, water vapor, and CO2 across multiple canopy layers. Both IBM and MCANOPY are evaluated against field measurements, demonstrating good performances compared with observations. The updated modeling system (i.e., WRF-LES-IBM-MCANOPY) is then applied over a forest edge to investigate the effects of foliage distributions and scalar distributions on canopy flows and scalar transfer. The results show that foliage distributions have a significant impact on the flow dynamics and scalar transfer, mainly due to the sub-canopy jet. The scalar distributions affect the scalar field with the ground source being the most important. The modeling system also simulates flows over forested hills. Flow dynamics over a three-dimensional hill show a different feature to those over a two-dimensional hill, where much large turbulence structures are simulated in the lee of a three-dimensional hill. Simulations over different slope hills demonstrate significant impacts of slopes. The lee side turbulence is enhanced as the hill slope increases. A new flow feature is the nearly unvarying flow field within the canopy in the lee of a steep slope hill, subjected to the influence of foliage distributions. Our upgraded WRF-LES-IBM-MCANOPY system has demonstrated promising capacities in many applications such as wind-turbine siting, wildfire propagation prediction, and interpretation of eddy covariance data over complex landscapes.
Book Synopsis Using High-fidelity Computational Fluid Dynamics to Help Design a Wind Turbine Wake Measurement Experiment by :
Download or read book Using High-fidelity Computational Fluid Dynamics to Help Design a Wind Turbine Wake Measurement Experiment written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we describe the process of using large-eddy simulations of wind turbine wake flow to help design a wake measurement campaign. The main goal of the experiment is to measure wakes and wake deflection that result from intentional yaw misalignment under a variety of atmospheric conditions at the Scaled Wind Farm Technology facility operated by Sandia National Laboratories in Lubbock, Texas. Prior simulation studies have shown that wake deflection may be used for wind-plant control that maximizes plant power output. In this study, simulations are performed to characterize wake deflection and general behavior before the experiment is performed to ensure better upfront planning. Beyond characterizing the expected wake behavior, we also use the large-eddy simulation to test a virtual version of the lidar we plan to use to measure the wake and better understand our lidar scan strategy options. This work is an excellent example of a 'simulation-in-the-loop' measurement campaign.
Book Synopsis Analysis of Model-free Control of Wind Farms Using Large-eddy Simulations by : Umberto Ciri
Download or read book Analysis of Model-free Control of Wind Farms Using Large-eddy Simulations written by Umberto Ciri and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind farms are clusters of wind turbines deployed over a relatively small area. During operations, the wake from upstream turbines may impinge on trailing turbines causing a decrease in power production. Wind farm control strategies aim at mitigating the effect of wake interactions. In this dissertation, model-free control strategies for wind farm power maximization have been evaluated using numerical simulations of the flow through wind farms. A model-free approach does not require a priori assumptions on the physical system, but learns on-line the system dynamics, avoiding modeling uncertainties. The control strategies are based on extremum-seeking control (ESC), a real-time gradient-based optimization algorithm. Either the turbine generator torque or the rotor yaw angle is used as the control parameter tuned by ESC to optimize the wind farm power production. The generator torque adjusts the turbine angular speed and the momentum deficit in the trailing wake, while the yaw angle serves to vary the direction of the wake and avoid trailing turbines. We first consider several implementations of ESC and assess their performances and practical feasibility. Both torque- and yaw-based ESC enhance power production, but the latter has a larger margin for improvement. For idealised turbine arrays, ESC achieves a potential power improvement of at least 7–8% compared to operations with design settings for an isolated turbine. After this calibration, we perform an optimization study for a real wind farm and obtain a quantitative evaluation of the impact of the control strategy in annual energy production. Large-eddy simulations with rotating actuator disk are used, in the first place, to provide a virtual wind farm to test the control algorithms. Additionally, the numerical data are investigated to gain a physical insight on the mechanisms underlying the performance improvement and broaden the impact of the optimization.
Book Synopsis Large Eddy Simulation of Wind Turbine Wakes. Detailed Comparisons of Two Codes Focusing on Effects of Numerics and Subgrid Modeling by :
Download or read book Large Eddy Simulation of Wind Turbine Wakes. Detailed Comparisons of Two Codes Focusing on Effects of Numerics and Subgrid Modeling written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we report on results from a detailed comparative numerical study from two Large Eddy Simulation (LES) codes using the Actuator Line Model (ALM). The study focuses on prediction of wind turbine wakes and their breakdown when subject to uniform inflow. Previous studies have shown relative insensitivity to subgrid modeling in the context of a finite-volume code. The present study uses the low dissipation pseudo-spectral LES code from Johns Hopkins University (LESGO) and the second-order, finite-volume OpenFOAMcode (SOWFA) from the National Renewable Energy Laboratory. When subject to uniform inflow, the loads on the blades are found to be unaffected by subgrid models or numerics, as expected. The turbulence in the wake and the location of transition to a turbulent state are affected by the subgrid-scale model and the numerics.
Book Synopsis Large Eddy Simulation of Dynamically Controlled Wind Turbine Arrays by : Rupert C. Storey
Download or read book Large Eddy Simulation of Dynamically Controlled Wind Turbine Arrays written by Rupert C. Storey and published by . This book was released on 2014 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate prediction of transient wind turbine wakes is important for the siting of turbines within wind farms due to wake structures that can affect downwind turbine performance and loading. A technique is described for coupling large eddy simulation of the wind with an aero-elastic turbine simulation to dynamically model both turbine operation and the genesis of wake structures. The important feature of this approach is a turbine model which actively responds to transient wind conditions in a flow simulation through the inclusion of the dynamic turbine state and controller actions. The codes are coupled through a newly developed actuator model and a software framework to transfer data between simulations. The resulting system is computationally efficient, with the ability to model multiple turbines exhibiting standard baseline control, operating in an atmospheric boundary layer flow. Simulations demonstrate the successful implementation of the coupled methodology with results showing good agreement with measured data and benchmark load distributions. The flow within a four turbine farm has been analysed at several wind speeds, quantifying power losses and increased load fluctuations on downwind turbines. Increased control utilisation is also observed in wake-affected rows, along with wake meandering phenomena. The implementation of transient boundary conditions has demonstrated the ability to model extreme transient wind conditions in a turbine array simulation. Results illustrate the propagation of wind event fronts, and quantify the response of the turbines with significant pitch and yaw actuation observed.
Book Synopsis Complex Effects in Large Eddy Simulations by : Stavros Kassinos
Download or read book Complex Effects in Large Eddy Simulations written by Stavros Kassinos and published by Springer Science & Business Media. This book was released on 2007-07-16 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of Large Eddy Simulations is reaching a level of maturity that brings this approach to the mainstream of engineering computations, while it opens opportunities and challenges. The main objective of this volume is to bring together leading experts in presenting the state-of-the-art and emerging approaches for treating complex effects in LES. A common theme throughout is the role of LES in the context of multiscale modeling and simulation.
Book Synopsis A Large-eddy Simulation Study of Wake Propagation and Power Production in an Array of Tidal-current Turbines by : Matthew J. Churchfield
Download or read book A Large-eddy Simulation Study of Wake Propagation and Power Production in an Array of Tidal-current Turbines written by Matthew J. Churchfield and published by . This book was released on 2011 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents our initial work in performing large-eddy simulations of tidal turbine array flows. First, a horizontally-periodic precursor simulation is performed to create turbulent flow data. Then that data is used to determine the inflow into a tidal turbine array two rows deep and infinitely wide. The turbines are modeled using rotating actuator lines, and the finite-volume method is used to solve the governing equations. In studying the wakes created by the turbines, we observed that the vertical shear of the inflow combined with wake rotation causes lateral wake asymmetry. Also, various turbine configurations are simulated, and the total power production relative to isolated turbines is examined. Staggering consecutive rows of turbines in the simulated configurations allows the greatest efficiency using the least downstream row spacing. Counter-rotating consecutive downstream turbines in a non-staggered array shows a small benefit. This work has identified areas for improvement, such as the use of a larger precursor domain to better capture elongated turbulent structures, the inclusion of salinity and temperature equations to account for density stratification and its effect on turbulence, improved wall shear stress modeling, and the examination of more array configurations.
Book Synopsis Large Eddy Simulation and LIDAR 3-D Mapping for Optimization of Wind Power Generation in Limited-space Applications by : Kunpeng Zhu
Download or read book Large Eddy Simulation and LIDAR 3-D Mapping for Optimization of Wind Power Generation in Limited-space Applications written by Kunpeng Zhu and published by . This book was released on 2011 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: We use a recently developed high-resolution atmospheric large eddy simulation to determine the potential optimal locations for wind-powered turbines on OSU property. The Ohio State University (OSU) can increase its energy efficiency and reduce its carbon footprint by self producing some of the power it consumes with wind energy. The locations of future wind-powered turbines will have to fit within the existing constraints of building locations and forested park areas. Trees and building modify wind patterns and affect the efficiency of near-by wind turbines. In planning the optimal locations for future wind energy production, it is essential to have a tool that can resolve the effects of natural and manmade structures within a small, restricted-space property. Such a tool will be useful on the OSU campus and has broad commercial potential for middle-scale wind-energy produces. We used county mapping and LIDAR data to generate a 3-D map of the campus, which includes topography, land-use, buildings and vegetation at 3m resolution. The Regional-atmospheric-modeling-based Forest Large Eddy Simulation (RAFLES) resolves air flow and turbulence inside and above 3-D spatially explicit heterogeneous forest canopies and structures. We used a set of RAFLES simulations to develop a high resolution map of mean wind speed and turbulence on the OSU campus including the effects of current and planned campus buildings and green areas. These variables, combined with 30 years of weather data for Ohio were converted into "wind potential" maps that will be used to determine the optimal locations of wind-turbines, which are most efficient with a combination of strong wind with low turbulence. An ecological survey of vegetation and bird activity completes the picture by determining the potential impacts of turbine-induced micro-climatic changes.
Book Synopsis Implementation and Assessment of Turbine Wake Models in the Weather Research and Forecasting Model for Both Mesoscale and Large-eddy Simulation by :
Download or read book Implementation and Assessment of Turbine Wake Models in the Weather Research and Forecasting Model for Both Mesoscale and Large-eddy Simulation written by and published by . This book was released on 2010 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow dynamics in large wind projects are influenced by the turbines located within. The turbine wakes, regions characterized by lower wind speeds and higher levels of turbulence than the surrounding free stream flow, can extend several rotor diameters downstream, and may meander and widen with increasing distance from the turbine. Turbine wakes can also reduce the power generated by downstream turbines and accelerate fatigue and damage to turbine components. An improved understanding of wake formation and transport within wind parks is essential for maximizing power output and increasing turbine lifespan. Moreover, the influence of wakes from large wind projects on neighboring wind farms, agricultural activities, and local climate are all areas of concern that can likewise be addressed by wake modeling. This work describes the formulation and application of an actuator disk model for studying flow dynamics of both individual turbines and arrays of turbines within wind projects. The actuator disk model is implemented in the Weather Research and Forecasting (WRF) model, which is an open-source atmospheric simulation code applicable to a wide range of scales, from mesoscale to large-eddy simulation. Preliminary results demonstrate the applicability of the actuator disk model within WRF to a moderately high-resolution large-eddy simulation study of a small array of turbines.
Book Synopsis Large-Eddy Simulation Study of Wake Propagation and Power Production in an Array of Tidal-Current Turbines by :
Download or read book Large-Eddy Simulation Study of Wake Propagation and Power Production in an Array of Tidal-Current Turbines written by and published by . This book was released on 2011 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents our initial work in performing large-eddy simulations of tidal turbine array flows. First, a horizontally-periodic precursor simulation is performed to create turbulent flow data. Then that data is used to determine the inflow into a tidal turbine array two rows deep and infinitely wide. The turbines are modeled using rotating actuator lines, and the finite-volume method is used to solve the governing equations. In studying the wakes created by the turbines, we observed that the vertical shear of the inflow combined with wake rotation causes lateral wake asymmetry. Also, various turbine configurations are simulated, and the total power production relative to isolated turbines is examined. Staggering consecutive rows of turbines in the simulated configurations allows the greatest efficiency using the least downstream row spacing. Counter-rotating consecutive downstream turbines in a non-staggered array shows a small benefit. This work has identified areas for improvement, such as the use of a larger precursor domain to better capture elongated turbulent structures, the inclusion of salinity and temperature equations to account for density stratification and its effect on turbulence, improved wall shear stress modeling, and the examination of more array configurations.
Book Synopsis An Efficient Large Eddy Simulation Algorithm for Computational Wind Engineering by : Ronald G. Rehm
Download or read book An Efficient Large Eddy Simulation Algorithm for Computational Wind Engineering written by Ronald G. Rehm and published by Forgotten Books. This book was released on 2017-10-29 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from An Efficient Large Eddy Simulation Algorithm for Computational Wind Engineering: Application to Surface Pressure Computations on a Single Building, August, 1999 All demonstrate the capability of the methods by comparison either with wind-tunnel re sults or with full-scale measurements. The latter are difficult to obtain, may be unrepeatable and usually have large uncertainties. Wind-tunnel measurements, on the other hand, arecontrolled and more reproducible, and are commonly used for cwe assessment and valida tions. Wind-tunnel tests conducted by Flachsbart at the Goettingen Aerodynamics Research Establishment in 1932 were the first to point out the differences between aerodynamic pres sures on building models tested in uniform, smooth flow on the one hand and in shear flow on the other; typical results are reproduced in Wind Effects on Structures, [6] p. 173. Test ing in shear flow, simulating with various degrees of success the atmospheric boundary layer flow, became routine in engineering practice only in the 1960's. At that time Baines [7] reported a classic set of measurements of mean pressures in a wind tunnel under both smooth uniform flow and shear flow. Recently, in a systematic joint effort under the aegis of the Architectural Institute of Japan (au) computational results obtained by three universities and nine industrial institutes were compared with wind tunnel measurements conducted under test conditions specified in careful detail. Shear flow is associated with mechanical turbulence, which has been shown experimen tally to influence the flow-body interaction. The magnitude of this influence varies depending upon the situation at hand. For example, consider a building located in a city center. To simulate correctly wind effects on that building it is necessary to model not only the building itself but also the buildings surrounding it. The signature turbulence of those buildings is likely to dominate the incoming flow turbulence, that is, the turbulence in the undisturbed flow at a sufficiently large distance upwind of the set of buildings of interest (the signature turbulence of a body is the turbulence generated by the interaction of the incoming flow with that body). The simulation of the incoming flow turbulence may then be of secondary importance. Nevertheless, there are many instances-where the incoming flow turbulence can play a significant role. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
