Wake meandering and its relationship with the incoming wind characteristics: a statistical approach applied to long-term on-field observations

A Review on the Meandering of Wind Turbine Wakes

“…The amplitudes of meandering are found to grow in the downwind direction [76]. In wind farms, the meandering amplitudes are found to be larger for the turbines at downwind locations [67,75]. The wavelength is in the order of rotor diameter, as shown in [64][65][66].…”

“…Howard et al [64] found that the amplitude of wake meander is about 0.1D-0.2D, the wavelength of wake meander is about 1D, the downwind convection velocity of the wake meandering is about 0.5U h to 0.7U h for wake meandering of a model wind turbine (D = 0.13 m). Garcia et al [75] investigated the statistics of wake meandering using seven-month measurement of two aligned wind turbines (the distance between the two turbines is about 3D in the downwind direction depending on the wind direction) in a full-scale wind farm. The standard deviation of the wake center positions of the upwind turbine increases from 0.1D at 1D turbine downwind to about 0.2D at 3D turbine downwind, and increases further to about 0.3D at 4D turbine downwind and gradually decreases at further downwind locations when the second turbine is not directly in its downwind.…”

Automated Wind Turbine Wake Characterization in Complex Terrain

“…Remote sensing approaches, particularly application of lidars, are increasingly being leveraged to provide flow characterization for the wind energy industry (Risan et al, 2018;Mikkelsen et al, 2008;Berg et al, 2015) and can be used to characterize the 3dimensional wake volume as it evolves downwind from the wind turbine as well as providing concurrent freestream wind speeds 20 from upstream measurements (Barthelmie et al, 2018;Barthelmie et al, 2014). Doppler lidar deployed for wake characterization can either be installed on the wind turbine nacelle, where they have been shown to be effective for characterizing individual wakes from 2-6 D , or on the ground relatively close to the wind turbine (Doubrawa et al, 2016) or at a distance scanning towards the wake(s) (Torres Garcia et al, 2017;Barthelmie et al, 2014). It is frequently difficult to get permission to install a Doppler lidar on the nacelle, and there is often a desire to sample wakes from multiple wind turbines simultaneously, 25 thus most field campaigns for quantification of wind turbine wake characteristics involve Doppler lidar placed on the ground as here (Barthelmie et al, 2014;El-Asha et al, 2017;Iungo et al, 2013;Clifton et al, 2018).…”

Automated wind turbine wake characterization in complex terrain

“…Remote-sensing approaches, particularly application of lidars, are increasingly being leveraged to provide flow characterization for the wind energy industry (Risan et al, 2018;Mikkelsen et al, 2008;Berg et al, 2015) and can be used to characterize the three-dimensional wake volume as it evolves downwind from the wind turbine as well as to provide concurrent free-stream wind speeds from upstream measurements (Barthelmie et al, 2014. Doppler lidar deployed for wake characterization can either be installed on the wind turbine nacelle, where it has been shown to be effective for characterizing individual wakes from 2-6 D (Aitken and Lundquist, 2014), or on the ground relatively close to the wind turbine (Doubrawa et al, 2016) or at a distance scanning towards the wake(s) (Torres Garcia et al, 2017;Barthelmie et al, 2014). It is frequently difficult to get permission to install a Doppler lidar on the nacelle, and there is often a desire to sample wakes from multiple wind turbines simultaneously; thus most field campaigns for quantification of wind turbine wake characteristics involve Doppler lidar placed on the ground as shown here (Barthelmie et al, 2014;El-Asha et al, 2017;Iungo et al, 2013;Clifton et al, 2018).…”

“…The scan configuration described below is thus designed to permit continuous autonomous operation in the long-term period and balance having sufficiently high-density scans to permit identification of the wake (in both the time and space domains) while not defining too small an overall arc span that would preclude collection of a meaningful number of cases. This measurement strategy was informed by the wind climatology for the site, and results from the test experiment Perdigão 2015 (Vasiljević et al, 2017) indicated that the streamline deformation at and downwind of the ridge is highly variable and associated with a wide range of wake behaviour, including lofting and descending, and follows the terrain. In the following Sect.…”