Wing tip vortex structure behind an airfoil with flaps at the tip

In this work, the wing tip vortex structure behind a NACA 0015 airfoil with and without small flaps was studied using a Partical Image Velocimetry (PIV) system. The experiment was carried out in a low speed wind tunnel with a test section of 0.5 m × 0.5 m. The Reynolds number (Re), defined by the chord length of the wing (C), was 8.1×104. The angle of attack was fixed at 10°. The PIV measurements were made from 0 to 2C, measured from the trailing edge of the model. The dihedral angle of three flaps was −15°, 0° and 15°, respectively. Compared with the clean airfoil, the one with three flaps significantly changed the wing tip vortex structure, the vorticity and the core of the wing tip vortex. The occurrence of three flaps decreased the gradient of pressure on the two sides of the wing tip, which depressed wing tip vortex formation to some extent. Vortices shed from three flaps influence the evolution of the wingtip vortex generated by the base airfoil. The interaction of those vortices resulted in a weakening of the wing tip vortex.