## 1 Introduction  
Wind energy is one of the most widely used renewable energy sources and is favored by various countries because of its green and clean characteristics [1]. Due to the high air density and abundance of wind energy resources in cold regions, the installed capacity of wind turbines is 10% higher than that in other regions [2, 3]. However, due to the lower temperatures, the blades are prone to ice accumulation [4]. Once the blades of a wind turbine freeze, it will lead to a series of safety problems, such as increasing the noise and load, and even breaking the blades in severe cases [5, 6]. In recent years, many research results have been achieved in regard to the icing characteristics of wind turbine blades and changes in aerodynamic characteristics. In terms of blade icing characteristics, [PERSON] et al. conducted icing tests on a horizontal-axis wind turbine with a diameter of 1.05 m and found that most of the open ice accumulated at both the leading edge and the tip of the blades [7]. [PERSON] et al. investigated the impacts of different liquid water contents, incoming wind speeds, etc., on the icing of NACA0012 airfoils and obtained different icing shapes under different icing parameters [8]. [PERSON] and [PERSON] et al. selected NREL Phase VI as the test condition to study the influence of different parameters on icing distribution on a blade. The results showed that the greater the wind speed and the lower the temperature, the greater the influence on blade icing [9, 10]. [PERSON] et al. monitored ice formation on small wind turbines and evaluated the ice formation strength. It was shown that the ice geometries were similar to those of large wind turbines but with a significant increase in ice-forming intensity [11]. [PERSON] and [PERSON] et al. quantified ice distribution on horizontal-axis wind turbine blades and found that the ice thickness on the blades increased rapidly from the blade root to the blade middle, and then increasedslowly from the blade middle to the blade tip [12; 13]. [PERSON] et al. investigated the icing characteristics of offshore wind turbine blades by simulation. It was shown that an increase in liquid water content and medium volume diameter led to an increase in the amount of ice formed on the blade surface, while an increase in medium volume diameter expanded the surface adhesion of ice on the blade [14]. [PERSON] et al. conducted a numerical study of ice accumulation in a 5 MW wind turbine blade profile and found a streamlined ice shape at low temperatures and an angular shape at higher temperatures [15]. [PERSON] et al. found that blade airfoil symmetry affects ice accumulation, with more streamlined ice shapes observed along the leading edge for symmetrical airfoils compared with asymmetrical airfoils, by numerically simulating two symmetrical (NACA 0006 and 0012) and two asymmetrical airfoils (NACA 23012 and N-22) [16]. [PERSON] et al. selected NACA 0018 airfoils as their research subject and carried out icing tests with different TSRs under crime ice conditions. It was shown that when the TSR was less than 1, ice covered the entire blade surface and grew by layers. When the TSR was greater than 1, the ice layer was concentrated near the leading edge [17]. [PERSON] et al. investigated the blade of NACA7715 airfoils in a wind tunnel and showed that the icing area and the icing rate depend on the angle of attack and the wind speed and determined the relationship between them [18]. In terms of aerodynamic characteristics, [PERSON] et al. numerically simulated a static icing blade and calculated the power coefficients of a wind turbine before and after icing for different tip speed ratios. The results showed that the power coefficient decreased with an increase in the tip speed ratio [19]. [PERSON] et al. investigated changes in wind turbine aerodynamic performance during dynamic icing.