“From Butterfly to Wind Turbine”

Abstract

The lift force and vibration performance of a wind turbine blade with a ‘butterfly skin’ (metallic version of the butterfly scale) were experimentally investigated. Attention was initially directed to this problem by observation of the complex microstructure of the butterfly scale as well as other studies indicating a higher lift on butterfly wings, covered with scales. Results indicated that the ‘butterfly skin’ of an oscillating blade (the airfoil was NACA-230) increased the lift force by a factor of 1.15, and reduced both the damping coefficients by a factor of 1.37, and the frequency by a factor of 1.1. The modification of the aerodynamic effects on the turbine blade was due to an increase of the virtual air mass, which influenced the ‘butterfly skin’. The air cavity of the skin increased the virtual air mass by a factor of 1.14. The interaction mechanism of a ‘butterfly skin’ with a flow is also described.