Unsteady Airfoil Design Optimization with Application to Dynamic Stall

This proposal seeks to develop a practical and economical design tool, first in two dimensions, and subsequently in three-dimensions, for optimizing helicopter rotor configurations for dynamic stall alleviation. The approach will consist of defining a target unsteady load pro file for a pitching airfoil in two dimensions or three dimensional rotor con figuration and modifying the shape of the airfoil/rotor blades in a manner which minimizes the difference between the computed and target load distribution. The effective solution of this optimization problem requires that the sensitivities of the objective with respect to the shape design parameters be available, and these are to be computed by solving the corresponding time-dependent adjoint problem. Although adjoint methods have been developed extensively for fixed-wing steady-state optimization problems, the practical extension of these techniques to time dependent problems has been limited due to computational cost and complexity. The use of adjoint methods for time-dependent dynamic stall alleviation would represent a significant advance in the state-of-the-art of rotorcraft design methodologies and enable the development of more advanced rotor configurations with associated performance benefits.