H314 撓みやすい羽毛の空力特性

概要

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Flight feathers are known to exhibit extreme asymmetry while primaries of flightless birds are symmetric. The present study focuses on how flexibility in feathers affects aerodynamic characteristics. The analysis, which is based on the thin airfoil theory and thin shell theory, has been done. The derived integro-differential equation was solved by the orthogonal polynomial expansion. The approximate but closed-form solution by four terms reveals the characteristics of feathers with normal shaft configuration : (1) lift is reduced by negative camber developed by deformation as well as the higher trailing edge location than the leading edge : (2) the center of pressure is almost independent of the shaft position and located closer to the mid chord than that of a flat plate. A feather will be twisted at the shaft position close to the leading edge, and hence asymmetry in flight feathers results in reduction of lift. What does this reduction merit birds? It is an open question.
日本流体力学会の論文
2001-07-31