Turbulent Flow Over a NACA 4412 Airfoil at Angle of Attack 15 Degree

This paper presents the measured mean flow and Reynolds stresses results, obtained on the center-line plane of the airfoil, covering the boundary layers over the upper surface, the potential flow region and the wake downstream of the trailing edge, at α_a = 15°. The flying X-hot-wire probe was used to measure the U and V components of the flow field over the airfoil. An improved understanding of the physical characteristics of separation on the airfoil sections and in the region of the trailing edge is of direct value for the improvement of high lift wings for aircraft. From the study of the separation flow at angle of attack α_a = 15°, the following can be concluded: (1) An intermittent reverse flow region occurred near the trailing edge of the airfoil. A separation bubble occurred for a short period of time and was then swept away with the stream wise flow. (2) The angle of attack α_a = 15° corresponds to the position of maximum lift for a NACA 4412 airfoil section. (3) It is found that values of the Reynolds normal and shear stresses move away from the surface with downstream distance, and (4) In the wake region, relatively large values of Reynolds stresses occurred, which were related to the vertical oscillation in the lower wake.