The "real physics" perspective integrates these views. The wing acts as a pump, imparting momentum to the air. As the air flows past the wing, it is deflected downward (downwash). This change in the air's momentum vector requires a force, and the reaction to that force is lift. McLean argues that the pressure field is the bridge between the wing and the momentum change. The pressure difference on the wing's surface is the manifestation of the wing pushing the air down.
Potential flow (inviscid, irrotational) solves ∇^2 φ = 0 with u = ∇φ. It captures large-scale pressure distributions around streamlined shapes and produces lift in classic 2D airfoil theory (Kutta condition), but it cannot predict viscous drag (D’Alembert paradox) or boundary-layer separation. understanding aerodynamics arguing from the real physics pdf