Abstract
The coupling of passive structural response of flexible membranes with the flow over them can significantly alter the aerodynamic characteristic of simple flat-plate wings. The use of flexible wings is common throughout biological flying systems inspiring many engineers to incorporate them into small engineering flying systems. In many of these systems, the motion of the membrane serves to passively alter the flow over the wing potentially resulting in an aerodynamic benefit. In this study, the aerodynamic loads and the flow field for a rigid flat-plate wing are compared to free trailing-edge membrane wings with two different pre-tensions at a chord-based Reynolds number of approximately 50,000. The membrane was silicon rubber with a scalloped free trailing edge. The analysis presented includes load measurements from a sting balance along with velocity fields and membrane deflections from synchronized, time-resolved particle image velocimetry and digital image correlation. The load measurements demonstrate increased aerodynamic efficiency and lift, while the synchronized flow and membrane measurements show how the membrane motion serves to force the flow. This passive flow control introduced by the membranes motion alters the flows development over the wing and into the wake region demonstrating how, at least for lower angles of attack, the membranes motion drives the flow as opposed to the flow driving the membrane motion.
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Acknowledgments
The authors would like to acknowledge the support of both the Air Force Office of Scientific Research (AFOSR) through the grant FA9550-10-1-0152, under a program managed by Dr. D. Smith and the Florida Center for Advanced Aero Propulsion (FCAAP). The authors would also like to acknowledge Y. Abudaram for the developing and manufacturing the wings used in this study.
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This article is part of the collection Topics in Flow Control. Guest Editors J. P. Bonnet and L. Cattafesta.
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Timpe, A., Zhang, Z., Hubner, J. et al. Passive flow control by membrane wings for aerodynamic benefit. Exp Fluids 54, 1471 (2013). https://doi.org/10.1007/s00348-013-1471-0
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DOI: https://doi.org/10.1007/s00348-013-1471-0