Shape optimization of rotorcraft airfoils using a genetic algorithm

In this work, a genetic algorithm was implemented to perform an airfoil shape optimization with constraints applied to the airfoil cross-sectional area and pitching-moment coefficient. Constraints are enforced through the use of an augmented Lagrange penalty function. The design variables are formed through a class shape transformation approach with orthogonal, polynomial basis modes. The use of an orthogonal basis provides decreased levels of multicollinearity in higher-order design spaces, while still maintaining the completeness of lower-order spaces. The optimization methodology is demonstrated on the tip airfoil of a UH-60A baseline rotor. The design trade-offs of a new tip airfoil are investigated where the optimized tip section shows improvements in forward-flight performance in exchange for a small reduction in the rotor's stall margin.