Free forward flight of cicadas is investigated through high-speed photogrammetry, three-dimensional surface reconstruction and computational fluid dynamics simulations. We report two new vortices generated by the cicada's wide body. One is the thorax-generated vortex, which helps the downwash flow, indicating a new phenomenon of lift enhancement. Another is the cicada posterior body vortex, which entangles with the vortex ring composed of wing tip, trailing edge and wing root vortices. Some other vortex features include: independently developed left-and right-hand side leading edge vortex (LEV), dual-core LEV structure at the mid-wing region and nearwake two-vortex-ring structure. In the cicada forward flight, approximately 79% of the total lift is generated during the downstroke. Cicada wings experience drag in the downstroke, and generate thrust during the upstroke. Energetics study shows that the cicada in free forward flight consumes much more power in the downstroke than in the upstroke, to provide enough lift to support the weight and to overcome drag to move forward.

Cicada: a Heavy but Agile Flyer" is a fluid dynamic video submitted to Gallery of Fluid Motion in APS-DFD 2011. Comparing to other insects, cicadas can generate much higher lift to overcome their large body weight. The hidden mechanism may help in designing a Micro Air Vehicle (MAV) to carry large payloads. However, it is lack of literatures in discussing how cicadas use their wings to accomplish various flights. In this work, a high-speed photogrammetry system and 3D surface reconstruction technology are used to reveal cicada wing kinematics and deformation during a freely forward flight. The aerodynamic performance is studied using in-house immerse boundary method based Computational Fluid Dynamics(CFD) solver.