Abstract
Several species of birds have been known to invert in flight to lose altitude — a behavior known as whiffling. When the bird flies inverted, the flight feathers twist open to create gaps in the trailing edge of the wing, decreasing the lift produced by the wing. Gaps along the trailing edge of an aircraft wing were inspired by the feather rotation mechanism during whiffling, and asymmetrically applying these gaps on only one side of the wing produces a rolling moment due to the lift differential across the full wing. Previous experimental data and analytical estimates showed that whiffling-inspired gapped wings can produce a larger rolling moment coefficient than a conventional aileron, for a fraction of the actuation work. In the current work, we perform a computational study using Siemens STAR-CCM+ to estimate the work required to actuate nine gaps along the trailing edge of a whiffling-inspired wing and compare it to that of a representative aileron configuration. We show that the results of the simulation agree well with the prior experimental results. The results indicated that the work on the entire gap area may be higher than the work to deflect an aileron, however, the analytically estimated work on a smaller, more realistic, area corresponding to a gap cover was substantially lower than the work to deflect an aileron. These results provide evidence that sliding gaps that open in the plane of a wing require less work than deflecting an aileron into the flow for rolling moment coefficients above 0.0139. This computational validation is the first step in determining if smart materials can be used for this type of wing morphing. In all, the whiffling-inspired gapped wings could provide a far more energy-efficient method of roll control for energy-constrained fixed-wing uncrewed aerial vehicles than conventional ailerons, particularly at higher rolling moment coefficients.
