Flow and Wing Kinematics Measurements of a Tiny Insect in Flight

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). A computational algorithm that solves a sparsity-regularized linear inverse problem was used to extract the in-focus particles from PIV images. Additionally, two orthogonal synchronized cameras were used to implement 3D stereophotogrammetry to determine the insect’s position in the PIV measurement plane and measure 3D wing kinematics. The whitefly 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 chordwise Reynolds number of 14. We present 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, a medial spanwise flow during the fling as the wings create a V-shaped gap, and an induced vorticity during the power stroke.