Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session M19: Boundary Layers VII: Wind Turbine Interaction |
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Chair: James Brasseur, The Pennsylvania State University Room: 310/311 |
Tuesday, November 26, 2013 8:00AM - 8:13AM |
M19.00001: Turbulence-driven power fluctuations on a wind turbine: characterization in the spectral domain Leonardo Chamorro, Nicolas Tobin, Hyun J. Kim, Jin T. Kim Power and loading fluctuations experienced by wind turbines are mostly driven by the turbulent characteristics of the incoming flow, which limit their life span. Understanding the complex relation between wind turbine(s) and flow unsteadiness is key for the development of advanced controls and also in structural design. In this field study, we investigate the response of a 1kW wind turbine under various inflow conditions. The research is performed in the RE-TE Wind Energy Field Station of the University of Illinois. Synchronous measurements of the three velocity components of the incoming flow, turbine power and rotational speed of the rotor are acquired at a temporal resolution that includes the majority of the scales relevant for the problem. An array of sonic anemometers is used to characterize the incoming flow in the vicinity of the wind turbine. Insights on the scale-to-scale interaction between flow and the turbine are obtained as well as the linkage between their spectral structures. A comparison with a wind-tunnel experiment and full-scale setup suggest an apparent universal behavior of the spectral structure of the wind turbine power. [Preview Abstract] |
Tuesday, November 26, 2013 8:13AM - 8:26AM |
M19.00002: Streamwise evolution of statistical events and the triple correlation in a model wind turbine array Kyle Viestenz, Ra\'{u}l Bayo\'{a}n Cal Hot-wire anemometry data, obtained from a wind tunnel experiment containing a $3 \times 3$ wind turbine array, are used to conditionally average the Reynolds stresses. Nine profiles at the centerline behind the array are analyzed to characterize the turbulent velocity statistics of the wake flow. Quadrant analysis yields statistical events occurring in the wake of the wind farm, where quadrants 2 and 4 produce ejections and sweeps, respectively. A balance between these quadrants is expressed via the $\Delta S_o$ parameter, which attains a maximum value at the bottom tip and changes sign near the top tip of the rotor. These are then associated to the triple correlation term present in the turbulent kinetic energy equation of the fluctuations. The development of these various quantities is assessed in light of wake remediation, energy transport and possess significance in closure models. [Preview Abstract] |
Tuesday, November 26, 2013 8:26AM - 8:39AM |
M19.00003: The effect of two-bladed and three-bladed wind turbine rotors on fluxes of kinetic energy Dalton McKeon, Andrew Newman, Matthew Melius, Raul Cal, Luciano Castillo As energy is extracted by wind turbines in an array, the main mechanism entraining energy into the flow within the array has been shown to be turbulent kinetic energy flux. Experiments showing this relationship have utilized three-bladed rotors. The goal of this study is to describe fluxes of kinetic energy in arrays utilizing two-bladed and three-bladed rotors. In a wind tunnel, two 3 X 4 arrays of model wind turbines were exposed to neutrally stratified conditions, with one array using two-bladed rotors and the other using three-bladed rotors. Both arrays had three turbines with 3D spacing in the spanwise direction and four turbines with 6D spacing in the streamwise direction. Each rotor had a diameter of 12 cm. The power coefficient was matched so that the non-dimensional rate of energy extraction was the same for both arrays. Data was collected along the centerline of both arrays using PIV with vertical data planes parallel to the streamwise direction. A control volume bounded by the rotor top tip and bottom tip is considered and fluxes of kinetic energy are compared for two-bladed and three-bladed arrays. Preliminary results show similar trends for the fluxes in both arrays, but no direct scaling was found, indicating a more complicated dependence on the number of blades. [Preview Abstract] |
Tuesday, November 26, 2013 8:39AM - 8:52AM |
M19.00004: Flow event classification via conditional statistics of PIV data in a model wind turbine array Devin Knowles, Ra\'{u}l Bayo\'{a}n Cal Conditional statistics are employed in the analysis of velocity data taken on a 3x4 model wind turbine array in a scaled wind tunnel experiment. Dual Stereo Particle Image Velocimetry measurements of the incoming and wake flow fields are considered for the wind turbines in the first and fourth row positions along the centerline. Quadrant analysis is applied to the SPIV data for all components of the Reynolds stress tensor $\langle u_i u_j \rangle$. The flow events involving all three components of velocity are identified and characterized using this conditional averaging technique as proposed by Raupach.\footnote{Raupach, M. R., (1981), \emph{J. Fluid Mechanics}, \textbf{108}, 363 -- 382.} Particular attention is given to the out of plane component of velocity due to the 3-dimensional nature of the flow in the wind turbine wake. [Preview Abstract] |
Tuesday, November 26, 2013 8:52AM - 9:05AM |
M19.00005: The Structure of the Wind Turbine Array/ Atmospheric Boundary Layer Interface Luciano Castillo, Jensen Newman A structure based approach is taken to describe the interface between a scaled wind turbine array in a wind tunnel and the approximate atmospheric boundary layer above it. The principle interest is to identify the various types of structures which exist here and determine 1) the domain of their existence and 2) their role in the process of extracting energy from the mean flow above the wind turbine array. These goals are achieved by computing the proper orthogonal decomposition of particle image velocimetry data collected along the centerline of the scaled wind turbine array and projecting the instantaneous field onto the most energetic modes. The analysis is carried out behind the first four turbines in the array and reveals two distinct regions based on structural differences: The near wake which is dominated by small scale turbulence and the far wake which is dominated by larger scales. It is further shown that the majority of the energy extraction is done by the larger scales in the far wake. Further, it is shown that after the first turbine, the small scale turbulence in the near wake is often less energetic than existing larger scale turbulence in the inflow. [Preview Abstract] |
Tuesday, November 26, 2013 9:05AM - 9:18AM |
M19.00006: Kinetic Energy Transport in a Vertical-Axis Wind Turbine Array Matthias Kinzel, Daniel Araya, John Dabiri We present experimental results from a full scale array of vertical-axis wind turbines (VAWTs) under natural wind conditions. The wind velocities throughout the turbine array are measured using a portable meteorological tower with seven, vertically-staggered, three-component ultrasonic anemometers. These measurements yield detailed insight into the turbine wakes and the recovery of the flow velocity behind the turbines. Quadrant hole analysis is employed to gain a better understanding of the energy transport at the top and the bottom of the VAWT array. The results are compared to the flow in horizontal-axis wind farms as well as urban and plant canopies. Emphasis is given to the flow physics in the adjustment region of the canopy, i.e. the region where the flow transitions from an atmospheric boundary layer to a canopy flow. [Preview Abstract] |
Tuesday, November 26, 2013 9:18AM - 9:31AM |
M19.00007: Development of a Scaled Smart Wind Farm Suhas Pol, Amelia Taylor, Dalton Mckeon, Luciano Castillo, Isaias Perez, Ren Beibei, Jian Sheng, Carsten Westergaard, Aksak Burak, Guillermo Araya, Fazle Hussain A model wind farm consisting of 3X5 horizontal axis turbines with a rotor diameter of 4 m (to be expanded to 5X20 turbines of 2m diameter) is being developed on TTU campus. Real field turbine wake evolution and interactions will be studied by employing particle image velocimetry. A 10m tower upstream of the wind farm as well as a 200m tower located 500m from the site will be used to characterize the atmospheric condition and its influence on the wake evolution. Of particular interest is the role of coherent structures in the atmosphere and the wake on the downward transport of overhead momentum - hence the effectiveness of the wind farm. From the recorded data episodes of stable, unstable and neutral atmosphere will be conditionally sampled to understand the effect of atmospheric stability on wind farm dynamics. The effect of various turbine-turbine separation and orientation on the downward momentum transport will be studied -- quite feasible since the turbine models are portable. In addition to aerodynamic studies the facility we will also test control algorithms. [Preview Abstract] |
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