Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session A27: Focus Session: Wind Energy Fluid Dynamics I |
Hide Abstracts |
Chair: John Dabiri, Caltech Room: Ballroom I-IV |
Sunday, November 20, 2011 8:00AM - 8:13AM |
A27.00001: Computational and Experimental Studies of Turbulence in Wind and Hydrokinetic Energy: From Turbines to Farms Fotis Sotiropoulos, Seokkoo Kang, Xiaolei Yang, Leonardo Chamorro, Craig Hill, Roger Arndt Recent computational and experimental advances at the St. Anthony Falls Laboratory (SAFL) aimed at understanding the structure of turbulence past wind and hydrokinetic turbines and farms will be presented. A powerful computational framework has been developed for carrying out LES of turbulent flow past complete turbine configurations as well as large-scale wind farms. For the former, the geometrical details of the turbine are resolved on fine computational grids using the CURVIB method with a wall model (Kang et al., Adv. in Water Resources, 34(1), 98-113, 2011) while for the latter the turbines are parametrized as actuator disks. Laboratory experiments in the SAFL atmospheric boundary layer wind tunnel and a large water flume have provided data sets for model validation. The computed and experimental results yield novel insights into the structure of turbulence in turbine wakes and suggest strategies for optimizing layouts of multi-turbine arrays for maximizing energy capture. [Preview Abstract] |
Sunday, November 20, 2011 8:13AM - 8:26AM |
A27.00002: Panel method for the wake effects on the aerodynamics of vertical-axis wind turbines Udit Goyal, Dietmar Rempfer A formulation based on the panel method is implemented for studying the unsteady aerodynamics of straight-bladed vertical-axis wind turbines. A combination of source and vortex distributions is used to represent an airfoil in Darrieus type motion. Our approach represents a low-cost computational technique that takes into account the dynamic changes in angle of attack of the blade during a cycle. A time-stepping mechanism is introduced for the wake convection, and its effects on the aerodynamic forces on the blade are discussed. The focus of the study is to describe the effect of the trailing wakes on the upstream flow conditions and coefficient of performance of the turbines. Results show a decrease in Cp until the wake structure develops and assumes a quasi-steady behavior. A comparison with other models such as single and multiple streamtubes is discussed, and optimization of the blade pitch angle is performed to increase the instantaneous torque and hence the power output from the turbine. [Preview Abstract] |
Sunday, November 20, 2011 8:26AM - 8:39AM |
A27.00003: Fluid-Structure Interaction Modeling of Horizontal- and Vertical-Axis Wind Turbines Yuri Bazilevs In this talk I will present a collection of numerical methods combined into a single framework for wind turbine modeling and simulation. I will cover our turbulence modeling and discretization approach, structural modeling and discretizations for wind turbine blades, the details of fluid-structure interaction (FSI) computational procedures focusing on the challenges of FSI coupling, and fluid mechanics domain mesh motion strategies in the presence of large rotation. I will present simulations of the NREL 5MW offshore baseline wind turbine rotor, including validation against published data. I will conclude by showing preliminary simulations of a vertical-axis wind turbine design. [Preview Abstract] |
Sunday, November 20, 2011 8:39AM - 8:52AM |
A27.00004: Quantitative Full-Scale Wind Turbine Flow Measurements Matthias Kinzel, Quinn Mulligan, John Dabiri To analyze the interaction between vertical axis wind turbines (VAWT) in detail it is important to gain a deeper understanding of their flow field. Quantitative in situ measurements pose a great challenge because of the large spatial dimensions, high flow velocities and remote locations of the VAWT. The aim of this work is to perform Particle Image Velocitmetry (PIV) in a horizontal cross section of a VAWT. The major difficulty is the choice of adequate seeding particles and illumination method for the large field of view, which is necessary. The flow velocities on the other hand require a high speed camera and the whole setup has to be powered self-sufficiently. However, PIV yields a two dimensional two component velocity field together with the out of plane component of vorticity and is therefore a considerable advantage over the single point measurements which are available today. The presentation will deal with different methods for seeding the flow. The properties of these flow tracers will be discussed and their ability to follow the flow reliably evaluated. Preliminary PIV results of the wind velocities at the test site will be shown. [Preview Abstract] |
Sunday, November 20, 2011 8:52AM - 9:05AM |
A27.00005: Novel Diagnostics to Investigate Turbine-Turbine Interactions B.J. Balakumar, S. Pol Strong aerodynamic interactions between upstream wind turbine wakes and downstream turbine blades cause fatigue loads and reduce turbine reliability. The wake structure also mediates the vertical flux of momentum and affects the power output of downstream turbines in turbine arrays. Despite their importance, our current understanding of wake-turbine interactions and wake structure is limited, especially under complex operating conditions such as yawed inflow and dynamic stall. Traditional diagnostics such as sonic anemometers, hotwires, and lidars suffer from interference and accuracy limitations and prove inadequate. At LANL, we have developed a Large Field-of-View Particle Image Velocimeter (LF-PIV) capable of measuring 3~m$\times$1~m (per camera) wake and inflow regions around a 5m-scale turbine. This scalable diagnostic operates in conjunction with a hub-mounted Rotating PIV (R-PIV) diagnostic to observe blade boundary layer and separation while the turbine is in operation. We discuss the diagnostic development challenges, solutions used to overcome these, and the interesting physics that these diagnostics promise to illuminate. [Preview Abstract] |
Sunday, November 20, 2011 9:05AM - 9:18AM |
A27.00006: Large Field of View Particle-Image Velocimetry (LF-PIV): Design and Performance Suhas Pol, John Hoffman, Balakumar Balasubramaniam We discuss the challenges and limitations associated with the development of a Large Field of View Particle Image Velocimetry (LF-PIV) diagnostic that is capable of resolving large scale motions (3m x 1m per camera) in gas phase laboratory experiments. While this diagnostic is developed for the measurement of wakes and local inflow conditions around research wind turbines, the design considerations provided here are also relevant for the application of LF-PIV to atmospheric boundary layer, rotorcraft dynamics and large-scale wind tunnel flows. Scaling laws associated with LF-PIV systems are presented along with the performance analysis of low-density, large diameter Expancel particles that appear to be promising candidates for LF-PIV seeding. Comparison of data obtained by LF-PIV measurements (2MP camera) and regular format sized PIV measurements show an agreement of within 1{\%} for mean velocity and 8{\%} for turbulent statistics respectively. [Preview Abstract] |
Sunday, November 20, 2011 9:18AM - 9:31AM |
A27.00007: Investigation on wind turbine wakes: wind tunnel tests and field experiments with LIDARs Giacomo Valerio Iungo, Ting Wu, Juliette C\"oeff\'e, Fernando Port\'e-Agel An investigation on the interaction between atmospheric boundary layer flow and wind turbines is carried out with wind tunnel and LIDAR measurements. The former were carried out using hot-wire anemometry and multi-hole pressure probes in the wake of a three-bladed miniature wind turbine. The wind turbine wake is characterized by a strong velocity defect in the proximity of the rotor, and its recovery is found to depend on the characteristics of the incoming atmospheric boundary layer (mean velocity and turbulence intensity profiles). Field experiments were performed using three wind LIDARs. Bi-dimensional scans are performed in order to analyse the wake wind field with different atmospheric boundary layer conditions. Furthermore, simultaneous measurements with two or three LIDARs allow the reconstruction of multi-component velocity fields. Both LIDAR and wind tunnel measurements highlight an increased turbulence level at the wake boundary for heights comparable to the top-tip of the blades; this flow feature can produce dangerous fatigue loads on following wind turbines. [Preview Abstract] |
Sunday, November 20, 2011 9:31AM - 9:44AM |
A27.00008: Experimental study of the kinetic energy budget of a wind turbine stream-tube Jose Lebron, Luciano Castillo, Charles Meneveau We consider the kinetic energy budget of a wind turbine stream-tube. Unlike the traditional Betz analysis, which neglects turbulence, we include the effects of turbulent kinetic energy fluxes at the stream-tube boundaries as well as dissipation of kinetic energy inside the stream-tube. The analysis is applied to a previously acquired PIV data set described in Cal et al. (2010, JRSE 2, 013106). Since the wind turbines in that experiment were lightly loaded, we observe that the stream-tube diameter changes by only 7{\%} and the mean velocity by 12{\%} between front and back of the wind turbine. Deviations from axisymmetry of the stream-tube are observed downstream of the wind turbine, mainly due to tower effects. Besides the importance of mean kinetic energy flux, we find that the radial Reynolds stress component acting on the stream-tube surface is a dominant contributor to the overall kinetic energy balance, and is responsible for the wake recovery. We also attempt to evaluate the turbulent dissipation rate by integrating the Reynolds stress times the mean velocity gradients inside the stream tube. [Preview Abstract] |
Sunday, November 20, 2011 9:44AM - 9:57AM |
A27.00009: Interaction of an Artificially Thickened Boundary Layer with a Vertically Mounted Pitching Airfoil Tristen Hohman, Alexander Smits, Luigi Martinelli Wind energy represents a large portion of the growing market in alternative energy technologies and the current landscape has been dominated by the more prevalent horizontal axis wind turbine. However, there are several advantages to the vertical axis wind turbine (VAWT) or Darrieus type design and yet there is much to be understood about how the atmospheric boundary layer (ABL) affects their performance. In this study the ABL was simulated in a wind tunnel through the use of elliptical shaped vortex generators, a castellated wall, and floor roughness elements as described in the method of Counihan (1967) and then verified its validity by hot wire measurement of the mean velocity profile as well as the turbulence intensity. The motion of an blade element around a vertical axis is approximated through the use of a pitching airfoil. The wake of the airfoil is investigated through hot wire anemometry in both uniform flow and in the simulated boundary layer both at $Re = 1.37\times 10^5$ based on the chord of the airfoil. [Preview Abstract] |
Sunday, November 20, 2011 9:57AM - 10:10AM |
A27.00010: Effect of Free-stream Turbulence on Flow Separation in S809 Wind Turbine Blade Sheilla Torres-Nieves, Victor Maldonado, Charles Meneveau, Luciano Castillo Two-dimensional Particle Image Velocimetry (2D-PIV) measurements are performed to study the effects of free-stream turbulence on the flow around a smooth and rough surface airfoil, specifically under stall conditions. A 0.25-m chord model with an S809 profile, common for horizontal-axis wind turbine applications, was tested at a wind tunnel speed of 10 m/s, resulting in Reynolds numbers based on the chord of 182,000 and turbulence intensity levels of up to 6.14\%. Analysis of the mean flow over the suction surface shows that, contrary to what is expected, free-stream turbulence is actually advancing separation, particularly when the turbulent scales in the free-stream are of the same order as the chord. This behavior is also confirmed by the examination of the aerodynamic coefficients; under stall conditions, the aerodynamic performance is slightly improved, from L/D~1.696 to 1.787. Further analysis of mean and turbulent quantities in the flow field will be performed in order to understand the mechanism by which free-stream turbulence is advancing separation. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700