Airfoil Optimization Based on an Evolution Strategy with Respect to Aeroelasticity

Numerical simulations are presented in order to test airfoil optimization criteria from the aeroelastic point of view. Based on an Evolution Strategy, airfoil-shape point optimization has been performed as a lift constrained drag minimization at a given Mach/Reynolds number combination for transonic flow. Additional to the drag minimization, the propagation time of pressure disturbances from the trailing edge to the leading edge above the suction side of the airfoil has been minimized. It could be shown that this minimization influences the unsteady flow field around the airfoil positively. In particular, the phase lag of the lift response to a harmonic pitch motion of the optimized airfoil is reduced compared with the value observed at the initial airfoil. Flutter calculations indicate that this change in the unsteady airloads reduces the collapse of the flutter boundary at transonic flow conditions well known as transonic dip.