Super Critical Aerofoil is a wing shape for Super Sonic Aircraft.
In this aerofoil when speed decreases from Super sonic to Sub- Sonic (Because shock waves always form from Super sonic to Sub sonic flow and not vice versa) instead of Shock waves, Expansion waves form and when air goes through them, Temperature, Pressure and Density all decreases,(instead of increasing as in normal Shockwaves.) Because Air is Expanding.
Reflex Curvature is a Special Aerofoil only found in the Super Critical Aerofoil structures.
It increases the flow of Boundary layer. It is on the trailing edge and guides the airflow to flow towards wing and thereby being at the upper trailing edge of the wing, the shock waves form behind the a/c, without disturbing the boundary layer over the wing.
Super Critical Aerofoil has a flat top surface and has Camber on the bottom side of the wing.
Shock waves form when air passes from Supersonic or Transonic airflow to Sub sonic flow, below 0.8 Mach no., and not when air passes from Sub sonic to Sub sonic.
For this reason, the upper area of the wing is kept flat and therefore velocity and pressure does not change and Shock waves do not form.
Reflex Curvature is an extended Aerofoil only found on Super Critical Aerofoil to increase the flow of Boundary layer, It is on the upper Trailing edge and guides the airflow to flow towards wing and thereby being at the upper Trailing edge of the wing, the Shock waves form behind the a/c, not disturbing the Boundary layer over wing.
Note- Shock waves forms only when air passes from Trans sonic to Sub sonic flow.