What is meant by the stagnation point of an airfoil?

• A. The point on the leading edge where airflow separates, some flowing over the top and some over the bottom.
• B. The trailing edge where the airflow reattaches.
• C. The center of pressure on the wing.
• D. The point of maximum lift on the upper surface.

Answer: (A)

The stagnation point is where the oncoming air meets the airfoil and the flow velocity relative to the surface drops to zero. At the leading edge, the air cannot occupy the solid, so it stops and then splits, with some flow continuing over the top and some over the bottom surfaces. That is exactly what this description conveys: a point on the leading edge where the airflow divides to go over both surfaces.

The trailing edge location where flow reattaches is related to flow separation and reattachment downstream, not where the velocity goes to zero at the surface. The center of pressure is the point where the resultant lift acts, a different aerodynamic concept. The point of maximum lift on the upper surface refers to a local lift distribution, not the stagnation behavior.