Optimization of Flexible Wings with Distributed Flaps at Off-Design Conditions

Abstract

An efficient process to aerodynamically optimize transport wings while addressing static aeroelastic effects is presented. The process is used to assess the aerodynamic performance benefits of a full-span trailing-edge flap system on a generic transport aircraft at off-design conditions. To establish a proper baseline, a transport wing is first aerodynamically optimized at a midcruise flight condition. The optimized wing is then analyzed at several off-design cruise conditions. The aerodynamic optimization is repeated at these off-design conditions to determine how much performance is lost by the wing optimized solely for the midcruise condition. The full-span flap system is then adapted to maximize performance of the midcruise-optimized wing at each off-design condition. The improvement due to the trailing-edge flaps is quantified by examining the degree to which the flaps can recover the performance of a wing designed specifically for the off-design condition. To evaluate the repercussions of aeroelasticity on the effectiveness of the flap system, this entire process is performed on both a conventional stiff wing and a modern, more flexible wing. The impact of the choice of flap layout is also explored. The results indicate that the flap system allows for significant improvement in performance throughout cruise and that it can be advantageous even for wings with increased flexibility. Moreover, the flaps appear to provide a means for active wave drag reduction during flight.