Читать книгу Flight Theory and Aerodynamics - Joseph R. Badick - Страница 94

Leonardo da Vinci stated the cardinal principle of wind tunnel testing nearly 400 years before the Wright brothers achieved powered flight. Near the beginning of the sixteenth century, da Vinci said: the action of the medium upon a body is the same whether the body moves in a quiescent medium, or whether the particles of the medium impinge with the same velocity upon the quiescent body. This principle allows us to consider only relative motion of the airfoil and the air surrounding it. We may use such terms as “airfoil passing through the air” and “air passing over the airfoil” interchangeably.