I've read in many places that centre of lift is about quarter chord of the wing and that post-stall lift (the part developed on lower surface) has centre midchord. The later makes sense; the pressure is distributed more or less uniformly (or at least symmetrically) on the lower surface. But what determines the centre of pressure on the upper surface?
The streamlines normally look like this:
and the pressure field like this:
But I've never seen explanation why the pressure should be lowest in the forward part (though it's the trailing edge that actually drives the circulation). Or can it only be explained by numeric calculation of the pressure and velocity field?
Also is it possible to describe (at least approximately) how this depends on the shape of the airfoil (like just flat plate or supercritical airfoil with the thickest point further aft) or is it again only possible by numeric calculation?