Surrogate-based optimization for airfoil trailing-edge noise reduction using morphed trailing-edge shapes

The purpose of this research is to find the optimal shape with lowest trailing-edge noise level. In the present paper, the airfoil geometry is morphed using the parametric airfoil design tool, which performs a paraemetersization with a baseline airfoil and a number of design parameters. In particular, a total of three design parameters are employed to change the trailing-edge shape: the starting point of trailing edge region, a boat-tail angle, and the measurement position of the boat-tail angle. The XFOIL is used to predict the aerodynamic performance and the input parameters for an empirical wall-pressure spectrum model. A predictive method that combines the empirical wall-pressure spectrum model with a diffraction model is used for the numerical analysis of airfoil trailing-edge noise. A design optimization framework using the Kriging surrogate model and the Genetic algorithm is developed, which is used to find the optimum solution for airfoil geometry that minimize the trailing-edge noise and simultaneously improve the aerodynamic performance. The optimized results are validated using the numerical method. It is found that the total trailing-edge noise level of optimized airfoil is significantly reduced, and the lift-to-drag ratio is improved in comparison with the baseline NACA0012 airfoil.