The above pictures from von Karman's Aerodynamics (1954) compares the lift coefficient for different angles of attack (left) and pressure distribution around a NACA 4412 airfoil, between Kutta-Zhukovsky circulation theory of lift and experimental values.
We see that the theoretical lift coefficient is too big and does not include the drop at stall at 16 degrees, and that the high pressure at the trailing edge from theory is not observed in experiments.
Von Karmann comments on p 46:
- The pictures show that the usefulness of the theory is restricted to a limited range of angles of attack, comprising relatively small angles, positive and negative. Beyond this range the measured values falls far below the values predicted by the theory.