In situ measurements of near wake dynamics with a fleet of multicopter drones

Abstract This study presents an analysis of wind turbine near wake vortices using a fleet of multicopter drones. Motivated by the need for accurate wake modeling for wind farm optimization, particularly in closely spaced layouts and repowering scenarios, the research addresses the limited availability of full-scale wake vortex data. While previous studies have employed numerical models, wind tunnel experiments, and single drone measurements, this work focuses on analyzing a larger dataset of in situ measurements. A methodology for automatic vortex detection and parameter extraction (circulation and core radius) from the drone fleet data is developed and applied to more than 300 observed vortices. The results demonstrate the feasibility of measuring vortex decay with this approach, indicating an expected increase in core radius with vortex age. The study also highlights the challenges and uncertainties associated with the method. Improvements are suggested for the future to locate drones slightly outside the expected wake area and in more streamwise distances downstream.