Experimental research of the boundary layer structure at near-critical angles of attack for the classical and wavy wings

The structure of the boundary layer on the classical and wavy wings at near-critical angles of attack at the Reynolds number Re = 140,000 is studied with the use of oil-film and infrared (IR) visualization. A boundary layer with a specific structure is demonstrated to form on the wing with the wavy surface. This boundary layer is more stable to separation from the wing surface. As a result, the wing with a wavy surface has a greater critical angle of attack and a greater maximum lift coefficient. Improvement of aerodynamic characteristics of the wavy wing, as compared with the classical wing, is confirmed by balance measurements.