# Collaborative Optimization of Aerodynamics and Wind Turbine Blades
## 1 Introduction
[PERSON] [34] developed a multi-objective optimization method for the aerodynamics and mechanics of a large-scale wind turbine blade using an evolutionary algorithm and extreme load calculation. [PERSON] et al. [35] proposed an aero-structure multi-objective optimization framework for a small wind turbine blade in which the coupling between structure and aerodynamics is considered. [PERSON] et al. [36] used a multi-objective genetic algorithm to carry out a coupled aerodynamic-structural optimization and obtained an improved distribution of both chord values and twist angle. [PERSON] et al. [37] proposed a discrete aero-structural multi-objective optimization framework for wind turbine blades in low wind speed areas. [PERSON] et al. [38] presented a coupled aero-structural multi-objective optimization method to simultaneously optimize the outer shape and the interior structural layout of a wind turbine blade. [PERSON] et al. [39] performed an aero-structural design and optimization exercise to reduce the blade mass/cost by obtaining the optimal blade chord and airfoil thickness. It is noted that in most studies on the coupled aero-structural optimization of wind turbine blades, a multi-objective optimization (MOO) strategy is preferred. Although MOO can provide a Pareto optimal solution, the collaboration between different disciplines is not comprehensively explored, especially in terms of inconsistency or conflict between disciplines. Multidisciplinary design optimization (MDO) provides an alternative to the aero-structural optimization of wind turbine blades. By establishing a hieratical optimization framework, MDO can improve optimization efficiency since parallel optimization of disciplines can be performed. Moreover, interdisciplinary inconsistency can be minimized [40]. In the field of wind turbine design, MDO has been applied to some aspects such as platforms, rotor blades, and towers. For example, [PERSON] and [PERSON] [41] defined an MDO process for a wind turbine blade to maximize aerodynamic efficiency and structural robustness. [PERSON] et al. [42] defined an MDO process that carries out a simultaneous optimization of the aerodynamic and structural characteristics of a swept wind turbine blade design. [PERSON] et al. [43] presented a design of a 100 kW bend-twist coupling blade with a monolithic MDO framework. [PERSON] et al. [44] offered an analysis of a wind turbine blade's aero-structural optimization based on an open-source MDO framework. [PERSON] et al. [45] proposed an MDO framework for an offshore wind turbine tower design. [PERSON] [46] developed an MDO framework for the aero-servo-elastic tailoring of a 20 MW wind turbine platform. [PERSON] et al. [47] used an MDO framework to perform aero-structural optimization of a wind turbine rotor using high-fidelity numerical simulation. In the study, a more comprehensive application of MDO in the aero-structural optimization of wind turbine blades is presented. A collaborative optimization (CO) framework is established to analyze the aerodynamic and structural disciplines simultaneously. The main contributions of the study include: (1) A CO framework is introduced to the design of wind turbine blades to improve optimization efficiency; (2) parameter sensitivity analysis is performed to determine the design variables in the aerodynamic and structural discipline analyses; (3) in the optimization loop, surrogate models are designed to replace the high-fidelity numerical simulation modules used for aerodynamics and structure analyses; (4) combined with a class function/shape function transformation (CST) method, parameterized modeling is carried out to obtain an airfoil design of the blade; (5) and the Isight integrated optimization platform is employed to achieve the automatic design and optimization of the wind turbine blades.