Volumetric Wind Field Reconstruction of Nacelle-based PPI Scanning Long-Range Lidar

An accurate hub height wind speed measurement by a Plan Position Indicator (PPI) scan from a nacelle-mounted long-range lidar is a challenging task due to the dynamic motions of the nacelle. This dynamic motion causes the actual lidar beam elevation to oscillate and measure wind speed above and below hub height as well. The long-range capability of the lidar resulted in higher sensitivity towards small inclinations. This master thesis explores the possibility of taking advantage of this motion to reconstruct a volumetric wind field from a PPI scanning lidar. The reconstruction involves the time accumulation of multiple PPI scans, which are then binned by the measured altitude. Velocity-Azimuth Display (VAD) is applied for each altitude bin to obtain binspecific wind direction. The horizontal wind direction is calculated from the measured line-of-sight velocity, vLOS, and estimated bin-specific wind direction. The wind field is presented in horizontal, vertical, and cross-sectional slices of the volume. This reconstruction approach is first validated through virtual experiment using a synthetic wind field from a Large-Eddy Simulation (LES) and then applied to a dataset from field measurements. The virtual experiment shows a good agreement between the reconstructed and reference wind fields. The application to field measurement shows the possibility to identify the complex, detailed structures of a wind field volumetrically. These results demonstrate the proposed reconstruction approach gives the opportunity for a better characterization and understanding of the measured wind field for wind energy applications.