The origin of lift revisited: I. A complete physical theory

We revisit the theoretical basis and underlying physical mechanisms of the most fun-damental problem in flight science-the origin of lift, confined to the simplest but most fundamental case for incompressible and steady flow past a two-dimensional airfoil with sharp trailing edge. After a review on the conceptual and theoretical evolution of the lift problem, we discuss the key issues including the critical role of viscosity in lift generation, the causal origin of vorticity in the airfoil circulation, and the detailed transient process by which the airfoil gains its circulation (to be reported in a companion paper as Part II of this work). A complete physical theory of lift generation is thereby constructed. ? 2015, American Institute of Aeronautics and Astronautics, Inc.EI1-1