Abstract
Wing of bird is a sophisticated organ for flying in various conditions. One typical example is a primary feather that is supposed to attenuate the wing tip vortex and thus contribute to reduce the induced drag. Although its great availability for the flight, the elasticity of feather causes the problem of flutter due to the coupling of the aerodynamic and the elastic forces. Interestingly, flutters are hardly observed in the primary feathers of flying birds. The reflection in the primary feather is supposed to be the key factor of flutter inhibition. The wind tunnel tests with feather models composed of various types of reflection confirmed that the reflection effectively inhibited the flutter generation.
