The effects of wingtip modifications on the wake of horizontal axis wind turbines

We study the impact of a novel wingtip modification on the wake dynamics of a 10-MW horizontal axis wind turbine using delayed detached eddy simulation. We considered a baseline turbine without wingtip modifications and a turbine equipped with winglets. The results reveal that the winglet significantly alters the near and mid wake regions, increasing the velocity deficit and reducing turbulence intensity in the near wake while minimally affecting the far wake beyond the distance of nine rotor diameters. The vortex rings from the blade tips decay faster in the wake of the modified turbine, reducing the wake energy and vorticity. The budget of mean kinetic energy transport shows that the winglet reduces the turbulence production in the near wake while increasing the turbulence convection and production in the far wake region. To study the meandering in the far wake of two turbine configurations, the dominant Strouhal number and the standard deviation of the wake center were studied. The results indicated that the winglet does not notably affect the amplitude of the wake meandering. Furthermore, the winglet increased turbine power production by 4.5% and thrust by 1.5% while reducing power and torque fluctuations by 10%. Although the winglet affected near wake dynamics, its influence on the far wake is minimal, suggesting potential benefits for wind farm design where turbines are not closely spaced.