Aerodynamic optimization design of airfoil based on CST parameterization method

Airfoil parameterization method has a very important impact on final optimization result. It has significant influence on the optimization design efficiency and result. In this paper, CST (Class function/Shape function Transformation) method is introduced to describe the airfoil shape with different geometrical parameters: direct CST, perturbed CST, and mean camber and thickness distribution CST. These parameterization methods are applied to airfoil optimization and the corresponding design results and efficiency are compared with each other. Drag minimization of a transonic airfoil is studied, by using the direct CST method, the perturbed CST method, the mean camber and thickness distribution CST method and the Hicks-Henne parameterization method for different orders. The results show that, the above four parameterization methods have nearly identical drag reduction effect but the respective computational costs are quite different. The perturbed CST and mean camber and thickness distribution CST are more efficient than the direct CST method and Hicks-Henne parameterization method with almost equivalent number of design variables. To further compare the optimization effect of the perturbed CST and mean camber and thickness distribution CST under fourth order Bernstern polynomial, lift drag ratio maximization of a wind turbine airfoil is studied. The results and their analysis show preliminarily that mean camber and thickness distribution CST appears appreciably more efficient than the perturbed CST.