Aerodynamic design optimization of supersonic airfoils

Firstly, the aerodynamic performance of supersonic airfoils with different geometric shapes and relative thickness is compared and analyzed. Secondly, design optimization is implemented for the polygonal airfoils of 3.5% relative thickness by combining genetic algorithm (GA) and rapid aerodynamic engineering algorithm. The design optimization process makes the polygonal airfoil approach to be a quadrilateral in shape with the maximum thickness location moving to about 60% of the chord. As the angle of attack or Mach number increases, the lower surface will become thinner, the upper surface will become thicker and the maximum thickness location will move backward slightly. Furthermore, for the biconvex airfoil of 4% relative thickness, a two-step design optimization method is used. In the first step, class and shape transformation (CST) based on B-spline basis function is used combined with wavelet decomposition to enhance the local control and fairing abilities. A surrogate model based on proper orthogonal decomposition (POD) is chosen to reduce the computational workload. The second step optimization employs the steepest decent algorithm (SDA) based on the Navier-Stokes equations to correct the errors caused by POD method and wavelet decomposition in the first step optimization. The optimized airfoil approximates to be a quadrilateral in shape, with the maximum thickness location moving to 60%-65% of the chord and lift-to-drag ratio increasing by 7%. © 2015, Press of Chinese Journal of Aeronautics. All right reserved.