How does camber affect on critical aoa?

Question

i am pretty clear about why a higher camber would increase Clmax, but critical aoa.

one of the resources i read the graphic shows a greater chamber near the leading edge will increase Cl at different aoa and Clmax, a greater that of trailing edge will increase both Clmax and crtical aoa.(i can't post a link due to the web, i'm in china, really sorry for that)

as far as i know camber would increase the gradient which leads to a wilder separation, that's going to make the airfoil easier stall.

but on the other hand, may be a greater camber would increase the performance of aircrafts at larger aoa? like a leading edge flap?

i have went through a lot of conversations about camber-Cl curve relations, they are basically about Clmax.

many thanks

Answer 1

In the sub-sonic realm, where most people fly, we try to avoid flow separation, which essentially is a breakdown of the low pressure area above the wing.

Starting with a flat plate, as we raise Angle of Attack, at a given velocity, for a given chord (Reynolds number), a stable area of low pressure will form over the wing. Lift will increase as we raise AoA, until the airflow gets disrupted enough to collapse the bubble. This disrupted airflow reduces lift and greatly increases drag, and is known as "stall".

Increasing the camber from a flat plate keeps the airflow "smooth" at higher angles of attack, giving much greater available Coefficient of Lift. The Davis wing is a good example of a sub-sonic airfoil optimized for maximum Clift.

Choosing degree of camber is dependent on chord and airspeed to get optimal flow (best lift to drag ratio) for a given airspeed. There is a wealth of knowledge from 120 years of aviation experience to be had at www.airfoiltools.com.

Generally, increasing camber increases stall AoA.