Aerodynamic Optimization of Next-Generation High-Lift Configurations in Commercial Aircraft

Abstract

High-lift devices are key aerodynamic devices that provide commercial aeroplanes with adequate lift at low speed (when taking off and landing) to not only guarantee safety but also make operations efficient. Conventional mechanisms, such as slats, Krueger and Fowler flaps, though efficient have high drag penalty and produce unwanted noise in the air and therefore affect the fuel economy, environmental sustainability and noise conformity of the community. As the international regulations are tightening and the move towards aviation that is more greener, next-generation high-lift systems are forced to be designed in a way that ensures their desired aerodynamic performance not simply should render them less intrusion into the acoustic environment but also should be able to integrate easily with advanced wing architectures like natural laminar-flow wings and morphing wings. The presented paper builds and tests a complete aerodynamic optimization model that unites the high-fidelity calculation fluid dynamics (CFD) simulations, surrogate based multi-objective optimization, and the experiment supporting a wind-tunnel test. It is a systematic investigation of the design space of hybrid high-lift designs, including leading-edge Krueger-slat designs and morphing trailing-edge flaps, in order to trade-off the competing aims of maximising the lift augmentation, decreasing the drag penalty, and lowering the noise emission. Adjoin-based solvers and Pareto-front analysis are used in the optimization process to determine the trade-offs between aerodynamic efficiency and acoustic performance and reduced-order surrogate models are used to speed up convergence. Scaled wind-tunnel testing is used to confirm the computational results and to check that optimized configurations result in an increase in the lift-to-drag ratio of up to 12% on takeoff and of 6 dB reduction of the noise levels compared to conventional Fowler flap systems. Flow visualisation also shows that delayed separation and easier reattachment were found in the improved designs, which made them more useful to improve the performance of low speeds without negatively affecting the cruise efficiency. The findings demonstrate the potential of hybrid morphing high-lift architectures in assisting future sustainable commercial aircraft to provide a scalable approach which can lead to future generation of airframe design and help significantly in fuel savings, reduction of emissions and in observing the change in the current noise regulations.