Time-Resolved Micro PIV Measurements around a Freely Flying Tiny Insect

The aerodynamics of flapping flight by tiny, mm-scale insects is not well understood. These insects are thought to rely heavily on unsteady aerodynamic interactions between the wings such as the clap-and-fling maneuver to generate lift. One reason for this knowledge gap is the technical challenges arising from the minute time and length scales of tiny insects beating their wings at hundreds of Hz. Here we use a novel ultra-high speed brightfield micro PIV system to measure time-resolved (10 kHz) 2D flow fields generated by a freely flying sweetpotato whitefly (Bemisia tabaci). An orthogonally positioned and synchronized camera records wing and body kinematics and the position of the insect in the PIV camera’s measurement plane. The whitefly has wing and chord lengths of 1 mm and 0.38 mm, respectively, a wingtip speed of 0.7 m/s, a wingbeat frequency of 170 Hz, a chordwise Reynolds number of 26, and a flight speed of 70 mm/s. Flow fields show that, in the clap phase, a high speed jet of air with speeds reaching 0.5 m/s emanates downward from between the approaching wings. In the fling phase, air rushes down into the V-shaped gap between the wings and forms enhanced leading edge vortices. These flow features have not been previously measured in a freely flying tiny insect.