Lift per unit span = ρ × V × Γ Where ρ is density, V is freestream velocity, and Γ is circulation.
A wing is not a "suction machine." The low pressure on top is caused by the air following a curved path. For a fluid parcel to move in a curve, there must be a net inward force (centripetal force). That force comes from a pressure difference: lower pressure toward the center of curvature. The top of the wing is the center of curvature, so pressure drops. Section 4: The Circulation Explanation (The Mathematically Honest Version) In advanced physics, we use circulation (Γ). This is not a fiction; it is a measurable quantity: the line integral of velocity around a closed loop enclosing the wing. understanding aerodynamics arguing from the real physics pdf
Moving beyond "equal transit time" and other convenient fictions. Lift per unit span = ρ × V
"What goes in must come out (at the same time)." In a steady flow, the mass flow rate (density × area × velocity) is constant along a streamtube. If a streamtube narrows, velocity must increase. This is not a theory; it is a mathematical necessity. That force comes from a pressure difference: lower
Understanding Aerodynamics: Arguing from the Real Physics
Do not settle for stories that feel good. Test every explanation against Newton’s laws and the conservation of mass. If an explanation cannot account for a flat plate flying upside-down, discard it. Real aerodynamics is not magic; it is the beautiful, inevitable consequence of a solid object moving through a fluid that must obey three simple rules. Master those rules, and you master the air.