Analysis of Waked Wind Flow in Complex Terrain from Doppler Lidar Measurements

The paper presents case studies of atmospheric features, specifically wind turbine wakes, captured by scanning Doppler lidar measurements during the Wind Forecast Improvement Project-2 (WFIP-2) in the complex terrain of the Columbia River Valley.

Lidar data from the research site near the Arlington airport are analyzed for the duration of the experiment to identify periods of waked flow captured by lidar conical or Plan Position Indicator (PPI) scans at low (1.7- 1.8 degree) elevation angles which correspond to hub heights of specific turbines. Turbine wakes are visible on these scans as streaks of reduced velocity. The wake parameters were analyzed for a single wind turbine aligned with the prevalent wind directions, and velocity deficit is computed as a function of distance from the turbine. In addition to some cases of wind direction were selected to analyze wakes downwind of two turbines to better understand wake interaction between these turbines. The paper will present results of wake analysis for selected cases.