Experimental Characterization of Lift on a Rigid Flapping Wing

Abstract

Measurements of aerodynamic forces over flapping wings are challenging due to unsteady flowfields and rapidly changing structural loads. This represents an important limitation to the aerodynamic data currently available to researchers working on the aerodynamics of bioinspired flapping wings. This paper proposes the use of pressure-based instrumentation for flapping-wing testing and documents the comparison of two experimental methods to measure the aerodynamic lift generated during the stroke of a rigid flapping wing. The first approach uses a force transducer to measure the forces in air and vacuum, and the second approach uses pressure measurements taken on the surfaces of the wing. The results from both methods are used to validate each other and provide experimental data for a test case with easily simulated conditions. This paper describes the design of the test hardware required, including a custom flap stand, flap mechanics, and instrumented wing construction techniques. A series of flap tests were conducted with pressures measured only in air and force measurements taken both in air and in a vacuum. The data are evaluated with respect to noise, repeatability, and expected scaling trends. The pressure sensor and force transducer measurement strategies are compared based on their accuracy and flexibility.