Aerodynamic interactions of two airfoils in unsteady motion (Q5946874)

The flight of dragonflies and damselflies, which have two pairs of interfering wings, is obviously superior to that of other larger insects. They are capable of fast take-off, long-time hovering and quick manoeuvre. Scientists have always been fascinated by their flight. Here the authors study unsteady flow interactions between two airfoils that perform a simple but typical motion. In this motion, the two airfoils parallelly move forward and down with the same constant velocity and angle of attack after an initial start. This motion is representative of the downstroke motion of the wing sections for a dragonfly beating its wings in phase (parallel stroking). Dragonflies use parallel stroking for high-lift situations such as rapid accelerations, take-off and hovering (in these modes of flight, forces used for weight support or acceleration are produced mainly by the downstroke). Moreover, this motion is relatively simple. Therefore, it is chosen as the first step in this study of the unsteady flow interactions between the dragonfly fore- and hindwings. A numerical solution of Navier-Stokes equations using moving overset grids is employed in the study.