Kutta–Joukowski theorem
The Kutta–Joukowski theorem is a fundamental theorem in aerodynamics that relates the lift per unit span of an airfoil (and any two-dimensional body, including circular cylinders) translating in a uniform fluid at constant speed to the circulation of the velocity field, under conditions where the flow in the body-fixed frame is steady and unseparated. The theorem relates the lift generated by an airfoil to the speed of the airfoil through the fluid, the density of the fluid and the circulation around the airfoil.