Three Component Velocity Measurements in the Tip Vortex of a Micro-Air-Vehicle

An investigation into the characteristics of the wing tip vortex on a flexible wing micro-air-vehicle (MAV) was conducted. The Air Force Research Lab, Munitions Directorate designed a man-portable MAV with a 24" wingspan and 6" root chord to be used for battle damage assessment and reconnaissance or local surveillance. For this MAV, two prototypes have been produced. One has a rigid wing prepared from carbonfiber; the other has a flexible wing prepared from parachute-latex material attached to a carbon-fiber frame. The experiments were performed to investigate the wing displacement and wing tip vortex interaction, characterizing the differences and effects of wing displacement and the shifting and velocity of wing tip vortex between two prototypes placed in typical operating conditions. Initially, each aircraft model was mounted at the test section in the low speed wind tunnel and exposed to various angles of attack and wind conditions. An optical telescope was used to measure the wing tip displacement and a tri-axial hot-wire anemometer was used to capture the velocity profiles in the wind tunnel to characterize wing tip vortex system. The results indicate that the wing tip displacement of the flexible wing was approximately 8 times than that of the rigid wing in an unstalled condition. The data suggests that flexible wing has a denser core-distribution of velocity within the wing tip vortex and delays the angle at which separation occurs.