Aerodynamic and flow structure analysis of iced wind turbine airfoil

Abstract

The issue of icing on wind turbines presents a significant operational challenge, especially in northern regions of Canada, where cold climates and harsh winter conditions prevail. This buildup of ice increases mechanical stress on the turbines, potentially resulting in costly maintenance and even operational failures. Ice formation alters the aerodynamic properties of the blades, increasing drag, which can severely reduce performance, leading to energy losses. Two primary types of ice profiles that occur in such environments are glaze and rime. In this study, in the first section, the impact of two experimental ice profiles (glaze and rime) on the aerodynamic characteristics of the NACA 643-618 airfoil are investigated and compared with the clean airfoil. Large Eddy Simulation is used to do the simulation, at a Reynolds number of 137,000, with angles of attack ranging from -10° to 10° with 5° step. Also, the aerodynamic characteristics of a parametric ice profile on the mentioned airfoil are studied and compared with the clean airfoil, in addition to two experimental ice profiles. The results indicate that the lift coefficient increases consistently with the angle of attack across all iced airfoils. However, the drag coefficient exhibits fluctuating behaviour due to the varying aerodynamic profiles caused by the different ice profiles. Glaze ice significantly increases drag, particularly at higher angles of attack, leading to a more pronounced reduction in aerodynamic efficiency compared to rime ice. Furthermore, in all iced cases, the aerodynamic performance moves forward by 5° compared to Base. The second section investigates the flow structures of glaze and rime and the comparison with the clean airfoil at an angle of attack of 10°. Instantaneous flowfield data at the 30th-second timestep is analyzed through flow visualization techniques, including streamlines, velocity contours and Q-criterion iso-surfaces. Results reveal that ice accretion significantly alters separation points, enhances flow instability, and accelerates the transition to turbulence. The study also examines friction coefficients (Cf) to pinpoint separation and reattachment locations. Furthermore, turbulent kinetic energy and Reynolds stress components are evaluated, showing increased turbulence intensity and energy dissipation due to icing.