An Experimental Study of Flexible Membrane Wings in Flapping Flight

Abstract

An experimental study was conducted to assess the aerodynamic benefits of using flexible membrane wings for the development of flapping-wing Micro-Air-Vehicles (MAVs). The overall aerodynamic performances (i.e. time-averaged lift and thrust/drag generation) of two flexible membrane wings with different skin flexibility (i.e., a flexible nylon wing and a more flexible latex wing) were compared with those of a conventional rigid wing in order to assess the effects of skin flexibility (rigidity) of the tested wings on their aerodynamic performances for flapping flight applications. The measurement results revealed clearly that, for all the tested wings, flapping motion would bring significant aerodynamic benefits when the flapping flight is in unsteady state regime with advance ratio of the flapping flight being smaller than 1.0. The aerodynamic benefits of flapping flight were found to decay exponentially with the increasing advance ratio. Flapping motion was found to become detrimental for high speed flight applications. The skin flexibility (rigidity) of the tested wings was found to have considerable effects on their aerodynamic performances for both soaring flight and flapping flight applications: The flexible membrane wings were found to have better overall aerodynamic performance (i.e., lift-to-drag ratio) over the rigid wing for soaring flight, especially for high speed soaring flight applications. The rigid wing was found to have better lift production performance for flapping flight in general. The latex wing, which is the most flexible among the three tested wings, was found to have the best thrust generation performance for flapping flight. The less flexible nylon wing, which has the best aerodynamic performance for soaring flight applications, was found to be the worst for flapping flight applications.