Received: 10 May 2022 – Discussion started: 23 May 2022
Abstract. Ice accretion on wind turbine blades causes both a change in the shape of its sections and an increase in surface roughness. This leads to degraded aerodynamic performances and lower power output. A high-fidelity multi-step method is here presented and applied to simulate a 3-hour rime icing event on the NREL 5 MW wind turbine blade. Five sections belonging to the outer half of the blade were considered. Independent time steps were applied to each blade section to obtain detailed ice shapes. The effect of roughness on airfoil performance was included in CFD simulations using an equivalent sand-grain approach. The aerodynamic coefficients of the iced sections were computed considering different roughness heights and extensions. The power curve before and after the icing event was computed according to the Design Load Case 1.1 of the International Electrotechnical Commission. In the icing event under analysis, the decrease in power output strongly depended on wind speed and, in fact, tip-speed ratio. Regarding the different roughness heights and extensions along the blade, power losses were qualitatively similar, but significantly different in magnitude, despite the presence of well-developed ice shapes.
Ice roughness deteriorates wind turbine aerodynamics. We have shown that this also occurs when complex ice shapes are present, as long as a large portion of the blade is frozen and roughness elements are high enough. Such features are typical of icing events on wind turbines. However, current icing simulation tools cannot capture them. Thus, future research on the topic should focus on correctly computing both the wet region of the blade and the roughness height.
Ice roughness deteriorates wind turbine aerodynamics. We have shown that this also occurs when...
