Formation, structure, and development of near-field wing tip vortices

Abstract

The current experimental study investigates the details of the formation, structure, and development of wing tip vortices that are generated by an aerofoil of NACA0012 profile having a rectangular planform of 151 mm chord using the particle image velocimetry technique. Experiments have been carried out at different angles of attack, which affect the vortex strength, vortex size, tangential velocity, and vorticity distribution along the downstream stations at chord lengths ranging from x/ c = 0.1 to 1.6, at a fixed free-stream velocity of 212 mm/s corresponding to the Reynolds number, Rec = 32 000 based on the chord length. The radius of the vortex core is found to vary approximately between 5 and 7.5 per cent of the chord length of the wing. The results show that the flow around the tip is dominated by the structures of multiple vortices. The maximum normalized tangential velocity increases with increasing angle of attack. The peak magnitude of the tangential velocity is ∼15 per cent of the free-stream velocity for an angle of attack of α = 4°, whereas it is ∼40 per cent of the free-stream velocity for α = 12°.