To fix the ideas, let's consider an airfoil instead of a generic shape.
As far as I understand, the separation of the boundary layer takes place after there is a region of reversal flow on the suction side of the airfoil.
In the other hand, I can find that the separation point is different from the point of reversal flow.
For me, this raises a question if it is possible to have a separation point on the suction side of the airfoil without having any reversal flow point? in other words, is it possible for the boundary layer to separate be it laminar or turbulent without having first a region of reversal flow? or maybe is the flow reversal a necessary condition for the boundary layer to separate?
Could you please provide me a pointer?