Near-wake measurements and simulations of a floating wind turbine using a four-beam nacelle-based lidar

Recent advances in lidar technology have expanded the possibilities for measuring full-scale wind turbine wakes within the atmospheric boundary layer. This study utilizes a four-beam pulsed lidar installed on the nacelle of a floating turbine to measure the near-wake. The wake measurement campaign was conducted on the Floatgen, with lidar measurements reaching up to 2.5 times the rotor diameter distance. These measurements are presented as 10-minute average radial wind speeds. The focus of this study is on the below rated wind speed of 7 m/s. Free flow conditions were assumed at the farthest measurement points, which are located +/- 0.9 times the rotor diameter from to the rotor center. The sensitivity of lidar measurements to turbulence intensity, vertical wind shear, and significant wave height was investigated. The environmental conditions were categorized into five cases, considering turbulence, vertical shear, and yaw misalignment as well as waves. Two simulation models with different fidelity levels are used to simulate these cases, and the beam-wise radial wind speed predictions are compared with the measurements. A maximum mean absolute error of 11.3% between the measurements and simulations is observed.