Numerical Optimization of Circulation Control Airfoils

Abstract

A numerical procedure for optimizing circulation control airfoils, which consists of the coupling of an optimization scheme with a viscous-potent ial flow analysis for blowing jet, is presented. Without losing the generality of the methodology, special attention is given to optimizing the blunt trailing edge, which has a direct bearing on the jet deflection characteristics. The desired airfoil is defined by a combination of three baseline shapes: cambered ellipse, cambered ellipse with drooped trailing edge, and cambered ellipse with spiraled trailing edge. The coefficients of these shapes are used as design variables in the optimization process. Under the constraints of lift augmentation and lift-to-drag ratios, the optimal airfoils are found to lie between those of the cambered ellipse and the drooped trailing edge, toward the latter as the angle of attack increases. Results agree qualitatively with the available experimental data.