Experimental investigation of wind turbine wake and load dynamics during yaw maneuvers

This article investigates the far wake response of a yawing upstream wind turbine and its impact on the global load variation in a downstream wind turbine. In order to represent misalignment and realignment scenarios, the upstream wind turbine was subjected to positive and negative yaw maneuvers. Yaw maneuvers could be used to voluntarily misalign wind turbines when wake steering control is targeted. The aim of this wind farm control strategy is to optimize the overall production of the wind farm and possibly its lifetime, by mitigating wake interactions. While wake flow and wind turbine load modifications during yaw maneuvers are usually described by quasi-static approaches, the present study aims at quantifying the main transient characteristics of these phenomena. Wind tunnel experiments were conducted in three different configurations, varying both scaling and flow conditions, in which the yaw maneuver was reproduced in a homogeneous turbulent flow at two different scales and in a more realistic flow such as a modeled atmospheric boundary layer. The effects of yaw control on the wake deviation were investigated by the use of stereo particle imaging velocimetry while the load variation on a downstream wind turbine was measured through an unsteady aerodynamic load balance. While overall results show a nondependence of the wake and load dynamics on the flow conditions and Reynolds scales, they highlight an influence of the yaw maneuver direction on their temporal dynamics.