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In order to optimize the wind turbine operation in ice prone cold regions, it is important to better understand the ice accretion process and how it affects the wind turbine performance. In this paper, Computational Fluid Dynamics (CFD) based 2D and 3D numerical techniques are used to simulate the airflow/droplet behaviour and resultant ice accretion on a 300 kW wind turbine blade. The aim is to better understand the differences in the flow behaviour and resultant ice accretion between both approaches, as typically the study of ice accretion on the wind turbine blade is performed using simple 2D simulations, where the 3D effects of flow (air & droplet) are ignored, which may lead to errors in simulated ice accretion. For 2D simulations, nine sections along a 300 kW wind turbine blade are selected, whereas for 3D study, a fullscale blade is used. The obtained results show a significant difference in the ice accretion for both approaches. Higher ice growth is observed in 2D approach when compared with the full-scale 3D simulations. CFD simulations are carried out for three different icing conditions (typical, moderate and extreme), in order to estimate the extent of differences the different operating conditions can introduce on the ice accretion process in the 2D and the 3D simulations. Complex ice shapes are observed in case of extreme ice conditions, which affect the aerodynamic performance of the blade differently from typical and moderate ice conditions.

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This paper describes a study to investigate the relation between ice accretion on a rotating wind turbine blade profile (airfoil) and a reference collector (circular cylinder). This relation, known as “k‐factor,” describes the ratio of accreted ice mass on a reference collector and wind turbine blade profile. Analyses are carried out by performing a series of multiphase numerical simulations and ISO 12494‐based analytical calculations. The results show that k‐factor is not equal to constant 20, contrary to currently postulated assumption by VTT and can vary to a significant degree depending on a number of different operating and geometric parameters. These factors include the effects of blade geometry on ice accretion, droplet collision efficiency, droplet distribution spectrum, and median volume diameter under different ambient conditions pertaining to wind speed and tip speed ratios experienced by both the reference collector and wind turbine blade. The results presented in this paper provide a simplistic explanation about k‐factor variance; however, further validation is necessary, in particular when it comes to the ice accretions on different wind turbine blade profiles under different operating and geometric conditions.