Measurement of unsteady fluid dynamic forces for a mechanical dragonfly model

An experimental study of the aerodynamics of a dragonfly in hovering flight is conducted. Measurements are made on a mechanical flapping wing apparatus that simulates, in water, the Reynolds number and reduced frequency of the tandem wing configuration on a dragonfly. The length scale of the flapping wing model is four times larger than on a real dragonfly. The phase difference between the flapping motions of the fore- and hindwings is independently varied in the range 0-90 deg to examine the flow interaction between the wings when the dragonfly is in hovering flight. The time histories and time average values of the fluid dynamic forces and the rate of work show that, in hovering flight, there is only a small interaction between the flows over the fore- and hindwings. The experimental data are also compared with the predictions of a three-dimensional Navier-Stokes code; these comparisons show good agreement and, thus, also verify the fidelity of the experimental data.