An improved methodology for airfoil shape optimization using surrogate based design optimization

This paper describes a Surrogate Based Design Optimization (SBDO) technique for airfoil shape optimization. The airfoil shape is parameterized in terms of B-Splines whose control points are used as design variables. Constraints are imposed on Maximum Camber and Thickness-to-Chord ratio of the airfoil. Optimum Latin Hypercube sampling is used to evaluate max. Lift/Drag (L/D) ratio for candidate airfoils, using XFOIL, an open-source aerodynamic analysis program. Using Kriging, a surrogate surface is created to obtain an approximate value of L/D for any set of design variables. Efficient global optimization algorithm is used to arrive at the optimum shape of airfoil for maximizing L/D at a specific angle of attack. The methodology resulted in profiles with 20% to 30% higher L/D than two baseline airfoils viz., Wortmann FX74 mod and Selig 1210, with several orders of magnitude lesser calls to XFOIL, as compared to a previous study, using teaching-learning based optimization technique.