Numerical simulations of ice accretion on wind turbine blades: are performance losses due to ice shape or surface roughness?

Abstract

Abstract. Ice accretion on wind turbine blades causes both a change in the shape of its sections and an increase in surface roughness. These lead to degraded aerodynamic performances and lower power output. Here, a high-fidelity multi-step method is presented and applied to simulate a 3 h rime icing event on the National Renewable Energy Laboratory 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 roughness effect on airfoil performance was included in computational fluid dynamics simulations using an equivalent sand-grain approach. The aerodynamic coefficients of the iced sections were computed considering two different roughness heights and extensions along the blade surface. 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 well-developed ice shapes. It was found that extended roughness regions in the chordwise direction of the blade can become as detrimental as the ice shape itself.

Towards blade-resolved ice accretion simulations of flexible blades using mixed-fidelity models

“…Thus, to finely solve ice accretion on each section a different time step ∆t ice can be used in the multi-step approach according to the radial position. Caccia and Guardone [5] have previously presented and applied this idea to a wind turbine rotor. The time step for multi-step accretion along the blade can be estimated using the non-dimensional ice accumulation parameter A c :…”

“…Indeed, ice detection systems can use the measurement of the evolution of the system eigenfrequencies [3,4]. In this context, the problem of fluid-structure interaction (FSI) adds to a complex multi-physics and coupled problem involving aerodynamics, particle-laden flows, heat transfer, and geometries changing 2 over time, leading to uncertain aerodynamic degradation of the rotor [5]. However, it is possible to reduce the complexity of the problem.…”

“…However, it is possible to reduce the complexity of the problem. Ice accretion can be either estimated with empirical correlations without considering the actual shape of the blade or simulated with a quasi-3D, quasi-steady approach relying on low-fidelity aerodynamic models such as the blade element momentum (BEM) theory, using their boundary conditions to solve the flow field around different blade sections [5]. The model proved reliable on wind turbines in simplified conditions when compared to full-3D simulations, considering a steady, uniform inflow and no yaw misalignment [6].…”

Ice Shape Convergence in Multi-Step Ice Accretion Simulations over Straight Wings

“…As shown in Fig. 1a, this results in an auto-amplifying phenomenon [8,9], which can hinder the stability of the multi-step procedure or lead to non-physical ice shape predictions.…”

A Wind Tunnel Test of the Anti-Icing Properties of MoS2/ZnO Hydrophobic Nano-Coatings for Wind Turbine Blades

“…However, as global climate change has intensified and extreme climates have become more frequent, wind turbines in these regions are at risk of blade icing, which reduces their aerodynamic performance and power generation efficiency. Blade icing also affects the safe operation of the system and increases maintenance costs [6][7][8]. Therefore, preventing or reducing blade surface icing on wind turbines has become a serious challenge in many engineering fields.…”