Important but somewhat complicated point: flight in a 2D world is a venturi effect, and regardless of altitude, a two-dimensional airfoil remains trapped in "ground effect mode." The circulation extends outwards indefinitely, and so an instant force-pair connects the wing with the surface of the Earth.
In 2D, the airfoil circulation creates lift upon the moving airfoil, but it also creates an equal down-force against the ground. If the airfoil was flying higher, the force pattern on the ground grows wider, but the net downforce doesn't change. As a result, 2D airfoil diagrams do not describe normal flight. They describe a sort of "Flatland flight" where no net work needs be done to accelerate mass downwards. As an explanation of aircraft, they've been simplified until they cross the line into actual error.
In the 3D world we can launch a vortex downward and experience a reaction force upward. Or perhaps launch a vortex sideways (during turns.) No instant-force upon the Earth is needed. The Newtonian force-pair arises between the mass-bearing aircraft and the mass-bearing air entrained by the shed vortex. Hovering rockets have an exhaust plume, and flying airplanes have a descending vortex-pair, and both are essential to any explanation. Real world 3D flight is "vortex-shedding flight," and the explanations based on 2D airfoil diagrams leads to no end of confusion.
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Important but somewhat complicated point: flight in a 2D world is a venturi effect, and regardless of altitude, a two-dimensional airfoil remains trapped in "ground effect mode." The circulation extends outwards indefinitely, and so an instant force-pair connects the wing with the surface of the Earth.
In 2D, the airfoil circulation creates lift upon the moving airfoil, but it also creates an equal down-force against the ground. If the airfoil was flying higher, the force pattern on the ground grows wider, but the net downforce doesn't change. As a result, 2D airfoil diagrams do not describe normal flight. They describe a sort of "Flatland flight" where no net work needs be done to accelerate mass downwards. As an explanation of aircraft, they've been simplified until they cross the line into actual error.
In the 3D world we can launch a vortex downward and experience a reaction force upward. Or perhaps launch a vortex sideways (during turns.) No instant-force upon the Earth is needed. The Newtonian force-pair arises between the mass-bearing aircraft and the mass-bearing air entrained by the shed vortex. Hovering rockets have an exhaust plume, and flying airplanes have a descending vortex-pair, and both are essential to any explanation. Real world 3D flight is "vortex-shedding flight," and the explanations based on 2D airfoil diagrams leads to no end of confusion.