Micro-PIV Measurements of a Tiny Insect Performing Clap and Fling

Tiny sub-millimeter insects in flight use the clap and fling mechanism to generate lift, but the aerodynamics of this mechanism are not well understood owing to the small spatial and fast temporal scales involved and the difficulty of experimentally observing the flow around the insect’s wings. To examine tiny insect flight, we implemented a novel ultra-high speed brightfield micro PIV system to measure time-resolved (10 kHz) flows generated by a freely flying sweet potato whitefly (Bemisia tabaci). An orthogonally placed and time synchronized camera was used to implement 3D stereophotogrammetry that was calibrated via direct linear transformation to determine the insect’s position in the PIV measurement plane, provide flow visualization, and measure body and wing kinematics. The whitefly, which has two pairs of high aspect ratio wings, has a body length of 0.8 mm, forewing length of 0.9 mm, hindwing length of 0.75 mm, stroke amplitude of 123^○, beat frequency of 150 Hz, and a chordwise Reynolds number of 14. We present time-resolved flow fields of the clap and fling, which reveals a downwards jet ejected from between the wings with flow speeds up to 400 mm/s during clap and a medial spanwise flow during the fling as the wings create a V-shaped gap.