Reply on RC2

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> 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.