편대비행 두루미의 에너지 절감 메커니즘

Abstract

A flapping flight mechanism of a Red-crowned crane (Grus japonensis) in migration was estimated using a two-jointed arm model having an unsteady aerodynamic performance. Inverse drag forces were generated and lift forces were enhanced during downstroke. A pair of flapping advantage vortices (FAV) was generated alternatively in the wake. The first fully developed FAV was developed around 6.6 m from the wing tip of the crane ahead. The width of FAV, corresponding to the wing tip spacing was about 0.62 m in the spanwise section. A crane behind saved about 18.5% of energy by using the induced power caused by FAV in V-formation and by changing wing morphology. Phase difference of flapping between the crane ahead and behind was estimated to be around 68.14° to use aerodynamic benefit caused by FAV. Our results can be applied to engineering flying devices.