söndag 5 augusti 2012
Unphysical Circulation Theory
The above left picture shows potential flow around a section of a circular cylinder with increasing circulation and associated lift starting from zero at top left. Lift from circulation is supposed to explain both the Magnus effect making a top-spin tennis ball curve down and the lift of a wing according to the Kutta-Zhukovsky circulation theory.
While it is true that circulation generates lift, it is not true that lift of rotating ball or a non-rotating wing comes from circulation: It is known since long that the Magnus effect is the result of unsymmetric separation, as shown in the picture to the right, and thus not from circulation. It is known from the New Theory of Flight that the lift of a wing is generated by 3d rotational separation and not from circulation around the wing section.
To understand that the left picture depicts an unphysical flow, it is enough to see that the whole flow is redirected and bent around the cylinder, with in particular the incoming flow changing direction, as if the mere rotation of the cylinder could change the flow upstream by some unknown magical effect.
The text book explanation of lift of a wing based on the incorrect unphysical Kutta-Zhukovsky circulation theory, which has dominated for a century, can now be replaced by a correct physical theory in accordance with observation, as required to make science.