Full-Scale Wind Turbine Near-Wake Measurements Using an Instrumented Uninhabited Aerial Vehicle

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
G. Kocer ◽  
M. Mansour ◽  
N. Chokani ◽  
R.S. Abhari ◽  
M. Müller
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Fast Response ◽  
Full Scale ◽  
Wake Flow ◽  
Near Wake ◽  
Simulation Tools ◽  
Wind Simulation ◽  
Aerial Vehicle

In this paper, the first-ever measurements of the wake of a full-scale wind turbine using an instrumented uninhabited aerial vehicle (UAV) are reported. The key enabler for this novel measurement approach is the integration of fast response aerodynamic probe technology with miniaturized hardware and software for UAVs that enable autonomous UAV operation. The measurements, made to support the development of advanced wind simulation tools, are made in the near-wake (0.5D–3D, where D is rotor diameter) region of a 2 MW wind turbine that is located in a topography of complex terrain and varied vegetation. Downwind of the wind turbine, profiles of the wind speed show that there is strong three-dimensional shear in the near-wake flow. Along the centerline of the wake, the deficit in wind speed is a consequence of wakes from the rotor, nacelle, and tower. By comparison with the profiles away from the centerline, the shadowing effects of nacelle and tower diminish downstream of 2.5D. Away from the centerline, the deficit in wind speed is approximately constant ≈ 25%. However, along the centerline, the deficit is ≈ 65% near to the rotor, 0.5D–1.75D, and only decreases to ≈ 25% downstream of 2.5D.

scholarly journals Investigation of the turbulent three-dimensional wind field in the near-wake of a full-scale wind turbine using synchronized scanning wind lidars

2021 ◽  
Author(s):  
Nikolas Angelou ◽  
Mikael Sjöholm ◽  
Torben Mikkelsen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Full Scale ◽  
Wake Flow ◽  
Free Flow ◽  
Wind Vector ◽  
Near Wake ◽  
The Mean ◽  
The Impact

<p>The objective of this work is to enhance the understanding of the mean wind and turbulence characteristics in the wake of a full-scale wind turbine.  Here, we present observations of the three-dimensional wind vector in the near wake of a wind turbine, a Vestas V52 with a 52-m rotor diameter.  The test turbine is located at the Risø campus of the Technical University of Denmark (DTU). The measurements were acquired using three, state-of-the-art, scanning, continuous-wave wind lidars, developed in DTU Wind Energy (<em>Short-Range WindScanner</em>). In our study, the area of focus was a vertical, two-dimensional plane at a distance of two rotor diameters from the wind turbine, in the downwind direction. Using the scanning lidars it was possible to derive spatially distributed estimations of the first and second-order moments of the wind vector within the vertical plane. The plane was within an area equal to 2.6 x 1.8 rotor diameters, towards the transverse and vertical direction respectively, covering a measuring range that included both the wake and free flow. The field test took place during a period of almost two weeks (July 2 - July 14, 2019). Approximately half of the time, the wind direction was favourable such that the measuring plane was covering a cross-section of the mean flow, which included the entire area where the wind speed deficit occurred. This data set enables the quantification of the wind speed deficit and the corresponding momentum deficit in the wake and reveals the turbulent layer that surrounds the mean wind speed deficit. Thus, allowing the investigation of the relation between the momentum fluxes and the local wind speed gradients, which is important for the understanding of the physical properties of the flow behind a wind turbine. Furthermore, we investigate the effect that wakes have on the vertical shear close to the ground, which can have a direct impact on the wind-surface interaction on the downwind side. Since the measuring plane was extended also to areas of the free flow, we compare the wind characteristics within the mean wake flow to the ones of the free flow. The knowledge of the features of the wake and the physical connection between the mean and turbulent flow provides a new detailed input for improved wake modelling. This is necessary for a more accurate prediction of the wake characteristics and can enable a more realistic quantification of the interaction between wind turbines in a wind farm, as well as the impact of the wake flow on the surrounding microclimate.</p>

PIV Experiment on Near Wake Flow of Horizontal Axis Wind Turbine

2013 ◽  
Vol 718-720 ◽  
pp. 1811-1815 ◽  
Author(s):  
Xiang Gao ◽  
Jun Hu ◽  
Zhi Qiang Wang
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Radial Direction ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Tip Vortex ◽  
Wake Flow ◽  
Horizontal Axis Wind Turbine ◽  
Near Wake ◽  
Piv Measurement

A three-dimensional horizontal axis wind turbine model was experimentally studied. The experiment was carried out in a laboratory wind tunnel. With PIV measurement, details about flow fields in the near wakeof the turbine blade were obtained. The result shows vortices generateon the tailing edge of the blade, and propagatedownstream then dissipate into small vortices. Vortices also generate at the tip of the blade, propagate downstream and along the radial direction then dissipate. The dissipation of the tip vortex is slower than the former. We also find that the wake of turbine blade rotates in the opposite direction of the blade.

Time-Resolved Near-Wake Measurements of a 2MW Wind Turbine

2013 ◽  
Author(s):  
Michel Mansour ◽  
Caglar Atalayer ◽  
Ndaona Chokani ◽  
Reza Abhari
Keyword(s):  
Wind Turbine ◽  
Real Time ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Fast Response ◽  
Near Wake ◽  
Time Resolved ◽  
Wind Speeds ◽  
Ultrasonic Anemometer ◽  
Yaw Angle

This paper presents time-resolved velocity measurements performed in the near wake of a multi-megawatt wind turbine, using a novel nacelle-mounted fast-response aerodynamic probe. The aerodynamic probe, which has been developed at ETH Zurich, consists of a hemispherical 5-hole probe equipped with fast-pressure sensors. The probe has a measurement uncertainty of ±0.1m/s and a measurement bandwidth of 65Hz. In addition to measurement of the three-dimensional wind velocity vector, the probe is instrumented for the real-time monitoring of meteorological conditions. The measured data are processed in real-time, stored on on-board and accessible via a GPRS modem. As the aerodynamic probe is installed adjacent to the wind turbine’s ultrasonic anemometer, the measurements of the two systems can be compared. The measured wind speeds are found to be in very good agreement and remains on an averaged within ±0.24m/s deviation to the ultrasonic anemometer. The measured yaw angle shows an average offset of −7.5°. This difference is observed since the ultrasonic anemometer does not accurately capture the turning of the flow across the wind turbine’s rotor. From the time-resolved measurements of the aerodynamic probe, the phase-lock averaged measurements show that over one blade passing period the turbulence intensity varies from 13 to 24%, with a maximum degree of anisotropy above 1.4. It is found that a hub passage vortex, which extends over more than 50% of the blade passage width, is present. Thus, from a turbine control perspective the actual placement of the ultrasonic anemometer, even when corrected, can lead to high yaw angle misalignment when the wind turbine is located in moderately or highly complex terrain.

Drone-Based Experimental Investigation of Three-Dimensional Flow Structure of a Multi-Megawatt Wind Turbine in Complex Terrain

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
B. Subramanian ◽  
N. Chokani ◽  
R. S. Abhari
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Direction ◽  
Complex Terrain ◽  
Wind Farm ◽  
Three Dimensional ◽  
Energy Yield ◽  
Near Wake ◽  
Tip Vortices

The aerodynamic characteristics of wakes in complex terrain have a profound impact on the energy yield of wind farms and on the fatigue loads on wind turbines in the wind farm. In order to detail the spatial variations of the wind speed, wind direction, and turbulent kinetic energy (TKE) in the near-wake, comprehensive drone-based measurements at a multi-megawatt (MW) wind turbine that is located in complex terrain have been conducted. A short-time Fourier transform (STFT)-based analysis method is used to derive time-localized TKE along the drone's trajectory. In upstream and in the near-wake, the vertical profiles of wind speed, wind direction, and TKE are detailed. There is an increase in the TKE from upstream to downstream of the wind turbine, and whereas, the characteristic microscale length scales increase with increasing height above the ground upstream of the turbine, in the near-wake the microscale lengths are of constant, smaller magnitude. The first-ever measurements of the pressure field across a multi-MW wind turbines rotor plane and of the tip vortices in the near-wake are also reported. It is shown that the pitch between subsequent tip vortices, which are shed from the wind turbines blades, increases in the near-wake as the wake evolves. These details of the near-wake can have an important effect on the subsequent evolution of the wake and must be incorporated into the three-dimensional (3D) field wake models that are currently under intensive development.

The Calculation of Train Slipstreams on Platform of Underground High-Speed Rail Station

2013 ◽  
Vol 842 ◽  
pp. 445-448
Author(s):  
Wei Chao Yang ◽  
Chuan He ◽  
Li Min Peng
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Horizontal Distribution ◽  
Wake Flow ◽  
Railway Tunnel ◽  
Long Distance ◽  
Near Wake ◽  
High Speed Rail ◽  
Numerical Work ◽  
Rail Station

This paper describes the results of numerical work to determine the flow structures of the slipstream and wake of a high speed train on platforms of underground rail station using three-dimensional compressible Euler equation. The simulations were carried out on a model of a simplified three-coach train and typical cross-section of Chinese high-speed railway tunnel. A number of issues were observed: change process of slipstreams, longitudinal and horizontal distribution characteristics of train wind. Localized velocity peaks were obtained near the nose of the train and in the near wake region. Maximum and minimum velocity values were also noticed near to the nose rear tip. These structures extended for a long distance behind the train in the far wake flow. The slipstream in platform shows the typical three-dimensional characteristics and the velocity is about 4 m/s at 6 m away from the edge of platform.

Near-Wake Flow Simulations for a Mid-Sized Rim Driven Wind Turbine

2013 ◽  
Author(s):  
Bryan Kaiser ◽  
Svetlana Poroseva ◽  
Erick L. Johnson ◽  
Rob Hovsapian
Keyword(s):  
Wind Turbine ◽  
Wake Flow ◽  
Near Wake ◽  
Flow Simulations

Experimental Investigation on the Tip Vortex of a Wind Turbine With and Without a Slotted Tip

2017 ◽  
Author(s):  
Pengyin Liu ◽  
Jinge Chen ◽  
Shen Xin ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Wind Turbine ◽  
Vortex Core ◽  
Control Method ◽  
Tip Vortex ◽  
Wake Flow ◽  
Core Model ◽  
Near Wake ◽  
Measured Velocity

In this paper, a slotted tip structure is experimentally analyzed. A wind turbine with three blades, of which the radius is 301.74mm, is investigated by the PIV method. Each wind turbine blade is formed with a slots system comprising four internal tube members embedded in the blade. The inlets of the internal tube member are located at the leading edge of the blade and form an inlet array. The outlets are located at the blade tip face and form an outlet array. The near wake flow field of the wind turbine with slotted tip and without slotted tip are both measured. Velocity field of near wake region and clear images of the tip vortex are captured under different wake ages. The experimental results show that the radius of the tip vortex core is enlarged by the slotted tip at any wake age compared with that of original wind turbine. Moreover, the diffusion process of the tip vortex is accelerated by the slotted tip which lead to the disappearance of the tip vortex occurs at smaller wake age. The strength of the tip vortex is also reduced indicating that the flow field in the near wake of wind turbine is improved. The experimental data are further analyzed with the vortex core model to reveal the flow mechanism of this kind of flow control method. The turbulence coefficient of the vortex core model for wind turbine is obtained from the experimental data of the wind turbine with and without slotted tip. It shows that the slotted tip increases the turbulence strength in the tip vortex core by importing airflow into the tip vortex core during its initial generation stage, which leads to the reduction of the tip vortex strength. Therefore, it is promising that the slotted tip can be used to weaken the vorticity and accelerate the diffusion of the tip vortex which would improve the problem caused by the tip vortex.

Numerical Studies of the Effects of Active and Passive Circulation Enhancement Concepts on Wind Turbine Performance

2006 ◽  
Vol 128 (4) ◽  
pp. 432-444 ◽  
Author(s):  
Chanin Tongchitpakdee ◽  
Sarun Benjanirat ◽  
Lakshmi N. Sankar
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Horizontal Axis Wind Turbine ◽  
Trailing Edge ◽  
Low Wind Speed ◽  
Gurney Flap ◽  
Coanda Jet

The aerodynamic performance of a wind turbine rotor equipped with circulation enhancement technology (trailing-edge blowing or Gurney flaps) is investigated using a three-dimensional unsteady viscous flow analysis. The National Renewable Energy Laboratory Phase VI horizontal axis wind turbine is chosen as the baseline configuration. Experimental data for the baseline case is used to validate the flow solver, prior to its use in exploring these concepts. Calculations have been performed for axial and yawed flow at several wind conditions. Results presented include radial distribution of the normal and tangential forces, shaft torque, root flap moment, and surface pressure distributions at selected radial locations. At low wind speed (7m∕s) where the flow is fully attached, it is shown that a Coanda jet at the trailing edge of the rotor blade is effective at increasing circulation resulting in an increase of lift and the chordwise thrust force. This leads to an increased amount of net power generation compared to the baseline configuration for moderate blowing coefficients (Cμ⩽0.075). A passive Gurney flap was found to increase the bound circulation and produce increased power in a manner similar to Coanda jet. At high wind speed (15m∕s) where the flow is separated, both the Coanda jet and Gurney flap become ineffective. The effects of these two concepts on the root bending moments have also been studied.

scholarly journals Investigation of an Innovative Rotor Modification for a Small-Scale Horizontal Axis Wind Turbine

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2649 ◽  
Author(s):  
Artur Bugała ◽  
Olga Roszyk
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Cfd Simulation ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Airflow Distribution

This paper presents the results of the computational fluid dynamics (CFD) simulation of the airflow for a 300 W horizontal axis wind turbine, using additional structural elements which modify the original shape of the rotor in the form of multi-shaped bowls which change the airflow distribution. A three-dimensional CAD model of the tested wind turbine was presented, with three variants subjected to simulation: a basic wind turbine without the element that modifies the airflow distribution, a turbine with a plano-convex bowl, and a turbine with a centrally convex bowl, with the hyperbolic disappearance of convexity as the radius of the rotor increases. The momentary value of wind speed, recorded at measuring points located in the plane of wind turbine blades, demonstrated an increase when compared to the base model by 35% for the wind turbine with the plano-convex bowl, for the wind speed of 5 m/s, and 31.3% and 49% for the higher approaching wind speed, for the plano-convex bowl and centrally convex bowl, respectively. The centrally convex bowl seems to be more appropriate for higher approaching wind speeds. An increase in wind turbine efficiency, described by the power coefficient, for solutions with aerodynamic bowls was observed.

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