Wake Deflection in Long Distance From a Yawed Wind Turbine

Since it is important to prevent the wake produced by upstream wind turbines from interfering with downstream wind turbines, a method of deflecting such wakes is desired. In this paper, we present the coupled analysis results of a computational fluid dynamics (CFD) simulation involving a three-bladed rigid wind turbine with a yaw control system that utilizes rFlow3D CFD code, which was developed by the Japan Aerospace Exploration Agency (JAXA), primarily for rotorcraft use. Herein, a three-dimensional (3D), compressible, and unsteady Reynolds-averaged Navier–Stokes (RANS) equation with a Spalart–Allmaras turbulence model is adopted as the governing equation. In this study, wind turbine computations using various wind turbine yaw angles are performed while focusing on the resulting wake velocity distribution and aerodynamic loads, after which the influences of the yaw angle are discussed. Next, based on the wake velocity distribution results for each yaw angle, we move on to a wake interference avoidance simulation for downstream wind turbines that utilizes two prepared wind turbines. Through this study, the following characteristics were confirmed. The results show wake deflection produced by adding yaw angle can provide a sufficient wake skew angle even in far-wake events. Furthermore, the yaw angle introduction accelerates the progression of vortex dissipation and brings about early velocity recovery in the wake region. Simultaneously, the introduction decreases the power generation amount of the yawed upstream wind turbine and increases the fatigue load of flapwise moment added to the blade root. In this paper, the details of flow field, oscillation, and the yawed wind turbine performance characteristics will also be described.