Multi-Element Winglets: Multi-Objective Optimization of Aerodynamic Shapes

Abstract

The wing tip device in this study was to mimic the wing tips of a soaring bird, featuring three smoothly blended elements. Each such multi-element winglet was integrated into a complete wing–tail–body aircraft configuration. The geometry of each of the three elements in the multi-element winglet was defined using 11 parameters, totaling 33 parameters for a complete multi-element winglet geometry. This design methodology used a three-dimensional geometry generation algorithm based on locally analytical smoothly connected surface patches, allowing for the creation of vastly diverse three-dimensional geometries with a minimal number of specified design parameters. A three-dimensional, compressible, turbulent flow, steady-state analysis was performed using a Reynolds-averaged Navier–Stokes solver on each configuration to obtain the objective function values. Each configuration was analyzed at a freestream Mach number of 0.25 and at an angle of attack of 11 deg to mimic the takeoff conditions of a passenger aircraft. Multi-objective optimization was carried out using modeFRONTIER, using a radial basis function response surface approximation coupled with a genetic algorithm. Maximizing coefficients of the lift and lift-to-drag ratio and minimizing the coefficients of drag and the magnitude of the coefficient of the moment were the four simultaneous objectives. The Pareto-optimized multi-element winglet concept demonstrated superior performance at subsonic and transonic speeds.