Airfoils

Aeronautics is now a branch of technology which offers tremendous potential for growth. Aero plane structure, shape and operation are very important for an aeronautical engineer. Airfoils are the cross sectional shapes of wings. General definition is that air foils are intersections with planes parallel to the free stream and normal to the plane of the wing. In a swept-back wings system, airfoils are defined in a plane perpendicular to the quarter chord line. Some concepts of fluid mechanics are required for the better understanding of essential characteristics of airfoils. Rounded leading edge is a must for air foils with the radius of curvature sufficiently large. This avoids excessive suction. Trailing edge of airfoils must be sharp. This is to establish Kutta- Joukowski condition. Wings should be made thicker (which makes a better structural beam). This allows load carriage with less structural weight. Six series airfoils were used in early jet engines. Then came peaky airfoils. Later NASA developed a high speed airfoil, supercritical airfoil with very small curvature over much of the upper surface so that the aft-facing surface has very little vertical projected area for a considerable distance behind the crest.