The two are not competing explanations but partners in a unified, coherent picture.
This is the "penalty" for creating lift. It occurs because the pressure difference at the wingtips causes air to curl into wingtip vortices , which consumes energy.
Moving away from the surface, the velocity increases until it matches the free-stream speed. This thin region of slowed-down air is called the . The Kutta Condition
Bernoulli's principle is valid, but only when we remove the "equal transit time" restriction. The wing forces air to bend around its upper surface. To follow this curved path, air must speed up. understanding aerodynamics arguing from the real physics pdf
Fluids have a natural tendency to follow a nearby contour due to viscous forces skinning the fluid to the solid boundary.
True aerodynamic lift is a holistic phenomenon governed by three immutable pillars of classical mechanics: Newton’s laws of motion, the conservation of mass (continuity), and the conservation of energy (Bernoulli's principle). They do not compete; they describe the exact same physical process from different perspectives. Flow Deflection and Newton's Third Law
For this to happen, the airflow must follow the contour of the wing. This behavior is heavily influenced by the Coandă effect, which is the physical tendency of a fluid jet to stay attached to a convex surface. Because air has viscosity (internal friction), it sticks to the upper surface of the wing and is deflected downward. Conservation of Momentum The two are not competing explanations but partners
Why argue from real physics?
Air molecules directly touching the wing surface stick to it completely, creating a "no-slip condition." This thin layer of slow-moving, sheared fluid is the boundary layer. Viscosity within this layer transfers kinetic energy between the wing and the free stream air. The Kutta Condition
Air does not simply shoot straight off a wing; it clings to the surface. This tendency of a fluid jet to stay attached to a convex surface is known as the . It occurs because the ambient air pressure pushes the moving fluid stream down against the surface. Moving away from the surface, the velocity increases
McLean’s central thesis revolves around the concept of "coupling." In incompressible flow, the pressure and velocity fields are inextricably linked. The "real physics" argument posits that the aerodynamic flow field is a solution to a global problem, governed by Newton’s laws and the continuity equation.
Aerodynamics studies how gases (usually air) move around bodies and how those flows produce forces and transport momentum, heat, and mass. Real aerodynamics roots predictions in conservation of mass, momentum, and energy applied to a continuum description of fluids, plus constitutive relations (e.g., Newtonian viscous stress, Fourier heat conduction) and appropriate boundary and initial conditions.