Countless arguments between highly intelligent people have been waged (on this very site in fact) as to exactly how lift can be explained in an experimentally and mathematically rigorous way. Taking the potential flow approximation and invoking the experimentally-observed Kutta condition provides a fairly accurate model. A majority of explanations for the Kutta condition involve Nature avoiding the infinite velocities implied by potential flow around a corner of zero radius. This, however, is where the problem arises. No man-made object has a zero radius of curvature. We cannot manufacture perfectly sharp corners in the same way that we cannot manufacture perfectly straight edges; all real objects have a nonzero radius of curvature. Thus, no potential flow would actually require an infinite velocity to properly flow around it. By this reasoning, claiming that Nature "enforces the Kutta condition to avoid infinite velocities" has to be false, because infinite velocities are not needed to flow around any real geometry. Moreover, we know that the Kutta Condition is actually not upheld for very low Reynolds numbers (see here and below). Is there a better explanation for the Kutta Condition than this spurious reference to infinite velocities? I know the potential flow model is just an approximation, but why does a real viscous flow force the rear stagnation point to the trailing edge?
From the MIT 16.100 Lecture Notes:
Hele-Shaw Flow Around an Airfoil (note that the rear stagnation point is not at the trailing edge):
A video of the above experiment can be seen here.