Bio-Inspired Gust Alleviation Based on Center-of-Percussion

Abstract

Recent experiments suggest that the European barn owl (Tyto alba) exploits alignment between the center of lift and the center of percussion on its wing to initially reject gusts. In flight, this morphological feature allows the owl's wing to passively deflect upwards and transfer no reaction force to its body for several milliseconds before the onset of active control. Accordingly, lift due to a sudden gust force is initially passively rejected. Herein, we investigate if this morphological adaptation may be of utility in engineered flight by testing how hinged wings with differing centers of percussion transmit forces. Four models are tested (three hinged, one rigid) with varying centers of percussion but a common center of lift. The results from the wind tunnel tests indicate a favorable relationship between center of percussion and center of lift. It was found that the model with the center of percussion closest to the center of lift had the initial reaction forces on the body in response to a gust reduced by 80.89%. Unsteady and quasisteady theoretical models are also developed with good agreement with experimental findings.