On airfoil research and development: history, current status, and future directions

Airfoils, which are the cross-section profiles of aircraft wings and tails, missile fins, helicopter rotor blades, and wind turbine propellers, play a particularly important role in determining the aerodynamic and overall performance. Since the invention of the first aircraft in the early 20th century, each breakthrough in airfoil research has dramatically promoted the upgrading of a better-performance aircraft. A large number of airfoil families, such as RAE, DVL, NACA, and TsAGI, either for general purpose or for particular types of aircrafts flying at different speed regimes, as well as airfoil families dedicated to helicopter rotors, propeller blades, and wing-turbine blades have been developed. In the 21^st century, high-fidelity numerical simulations, multi-objective multi-constraint optimization, flow instability analysis theory and transition prediction methods, and experimental testing techniques have been advanced progressively, which places a sound base for the development of new-generation airfoils. This article focuses on reviewing the recent progress on airfoil research after a brief review of over 100 years’ history of airfoil research and development. Future challenges as well as research directions are presented as the outcome of this review. With the strong need of developing future aircrafts and other aerodynamics-related equipments, a general trend of developing new-generation airfoils is to achieve better multidisciplinary performance when flying at wider speed ranges, larger airspace and multi-physics enviroments or intelligent morphing, which presents great challenges for numerical simulations, design optimization, and experimental validations.