# Collaborative Optimization of Aerodynamics and Wind Turbine Blades
## 1 Introduction  
Wind energy has become one of the most important renewable energy sources owing to its unique advantages including a clean, free, renewable resource in the form of wind, the economic value it brings, and the low costs of maintenance. In addition to windmills, wind turbines are the main wind devices used to convert the kinetic energy of wind into electricity. In general, two primary types of wind turbines are in use: horizontal-axis wind turbines (HAWTs) and vertical-axis wind turbines (VAWTs). Comparatively, HAWTs are the most commonly used type since this type of wind turbine offers greater efficiency in generating electricity. A typical HAWT possesses two or three blades that often resemble aircraft propellers in appearance. As a major part of HAWTs, the blade plays an important role in the overall operation of the wind turbine, being crucial to the turbine's efficiency and performance. A well-designed wind turbine blade can significantly increase energy production whilelowering maintenance and operating expenses. From the viewpoint of system engineering, designing wind turbine blades is a complicated procedure. Starting from specific needs such as power output and operating circumstances, designing wind turbine blades involves multiple domains such as aerodynamics, materials, structure, noise, and cost. Aerodynamics and structure are the main focus. In the optimization of aerodynamic performance, the airfoil and the aerodynamic shape of the blade are the main focus. Representative airfoils include the NACA 4-digital and 6-digital family [1; 2], the NREL-S family [3], the Ris \(\phi\) family [4], the DU family [5], and the FFA-W family [6]. Combined with design optimization, these airfoils are modified to achieve better aerodynamic performance. For example, [PERSON] and [PERSON] [7] obtained optimized airfoils by using a Kriging approximation model, in which the lift-to-drag ratio is increased by 81% compared with the original airfoil. Combined with numerical simulation, the approximation model-based optimization of wind turbine airfoils is confirmed [8]. Taking the maximum power coefficient as the objective and combining this with an airfoil noise prediction mode, [PERSON] et al. [9] obtained a new airfoil with a higher power efficiency and better aerodynamic performance. [PERSON] et al. [10] developed the NPU-WA airfoil family characterized by high lift under high Reynolds numbers. Combining a Hicks-Henne-type function and a multi-island genetic algorithm, [PERSON] [11] increased the lift-to-drag ratio of an airfoil by 15%. [PERSON] [12] developed the CQU-L airfoil family using Theodorsen theory and a B-spine curve-based integrated design method. [PERSON] et al. [13] studied the influence of different modification methods of the airfoil trailing edge on aerodynamic performance and proposed a trailing edge symmetrical thickening method. [PERSON] et al. [14] presented the optimization design of an airfoil based on a Bezier curve and bend function. Results show that under certain attack angles, the lift-to-drag ratio is increased by 29.8%. [PERSON] et al. [15] applied the differential evolution optimization technique to obtain optimal airfoils at various wind potentials. In addition to the airfoil, the aerodynamic shape of the blade exerts an important influence on wind turbine efficiency. Classic design methods of the aerodynamic shape of blades include the [PERSON] method [16] and the Wilson method [17]. Novel blade shapes can be obtained by either the Glauert or Wilson method. Afterward, the designs can be improved by means of optimization design. For example, based on the [PERSON] method and lifting line theory, [PERSON] et al. [18] developed a simplified model that reveals a potential for predicting improved and higher rotor performances. Based on [PERSON]'s blade element momentum theory, [PERSON] and [PERSON] [19] presented an iterative approach to optimizing the coefficient of power, the coefficient of lift, and the wind drag of a wind turbine rotor.