The relevance of spanwise flows for yawed horizontal-axis wind turbines

Abstract

The behaviour of spanwise flows close to the yawed wind turbine blade is investigated in this paper. These have seldom been studied in detail by wind turbine aerodynamicists. This work is of particular relevance because of the aerodynamic performance of the rotor highly depends on the magnitude and variations of these spanwise flows. This will help in creating better models which account for the complex aerodynamic behaviour which characterize wind turbine blades. The Model Experiments In Controlled Conditions (MEXICO) Stereo Particle Image Velocimetry dataset is used along with a 3D unsteady potential flow panel model. Spanwise induction is found to cause the total spanwise flow to differ from the sinusoidal behaviour of the freestream spanwise in-plane component. Also, the variation of the spanwise velocity with radius is close to linear along the blade span but becomes non-linear in the root and tip region. This analysis paves the way for a deeper understanding of the wake development mechanism.