Air-permeable hole-pattern and nose-droop control improve aerodynamic performance of primary feathers.

摘要: Primary feathers of soaring land birds have evolved into highly specialized flight characterized by morphological improvements affecting aerodynamic performance. The foremost in the cascade to bear high lift-loading with a strong bending during flight. A challenge study feather aerodynamics is understand how observed low drag and lift values Reynolds (Re) regime from 1.0 2.0E4 can be achieved. Computed micro-tomography images show that responds an increasing nose-droop profile-camber. Wind-tunnel tests conducted primary White Stork (Ciconia ciconia) at Re = 1.8E4 indicated surprisingly maximum coefficient 1.5 glide ratio nearly 10. We present evidence this due morphologic characteristics formed cristae dorsales as well air-permeable arrays along rhachis. Measurements forces open closed pores confirmed efficiency mechanism. Porous structures facilitate blow out, comparable technical blow-hole turbulators for sailplanes speed turbine-blades. From our findings, we conclude mechanism has order affect boundary layer reduce feather.