The study of tandem flapping wing aerodynamics of dragonflies in steady forward flight is presented here. CFD simulations of one forewing-hindwing pair are run using wing kinematics measured in experiments with free flying dragonflies. Wing kinematics were acquired from tests of dragonflies flying through a confined space using multiple high speed cameras, placed such that they could record the dragonfly's motion. The test results contain videos of dragonflies flying inverted as well as upright, and wing kinematics have been extracted for three inverted and two upright flights. In the inverted flights the upstroke is longer than the downstroke and the pitch angle of the forewing is lower during the downstroke than similar upright flights. Three simulations were run based on this kinematic information: one simulating upright flight, one simulating inverted flight, and one looking at the effect of changing relative downstroke duration. The simulation results indicate that the dragonflies are controlling the orientation of their wing such that they have a similar orientation relative to their velocity during the halfstroke when the wing is flapping down in the lab reference frame. In addition, decreasing relative downstroke duration increases peak and average lift, making it unclear why dragonflies use a longer downstroke than upstroke while flying upright.
展开▼
