Song and Breuer (2007) investigated the effects of aspect ratio and the initial tension of membrane wing on aerodynamic performance in mammalian flight by means of wind tunnel tests. Experiments of flexible wings have also been carried out. He highlighted the positive impact of the airfoil flexibility, which results from a close coupling between unsteady leading edge vortex shedding and dynamic response of structure. Gordnier (2009) presented numerical analysis for the aeroelastic model of a two dimensional flexible membrane airfoil. (2007) proposed a high-order discontinuous Galerkin method to study fluid–membrane interaction on the flapping flight. Researchers have attempted to explore the flexibility of structure to gain the potential of shape adaptation for severe flow condition, and to improve aerodynamic performance (Ghommem et al., 2012, Gordnier et al., 2013). In recent years, highly coupled fluid–structure systems for MAV at low Reynolds numbers have become of great interest inspired by biological flights. However, in most of these works (Dowell and Hall, 2001, Guo and Mei, 2003), the flow was modeled by using potential theory or thin-layer flow models, which cannot describe unsteady viscous flow precisely. An excellent review for these subjects is presented in Dowell and Hall (2001)'s work. Early studies have paid much attention to modeling of flexible structure and its aeroelastic instability (Dowell and Hall, 2001, Guo and Mei, 2003), such as flutter, limit cycle oscillation, chaotic motion. The investigation of the coupling system addresses a challenge of multi-disciplinary computational techniques and fundamental understanding of unsteady aerodynamics and fluid–structure interaction.Īn extensive study has been conducted on the coupling between the fluid flow and flexible structures. Thus the aerodynamic forces upon the structure will be altered in a feedback loop. On the other hand, since the structure is a boundary of fluid domain, the flow over the structure may change or separate. The structures may undergo severe vibration and large deformation under the unsteady aerodynamic forces. During the flight, unsteady flows and the structures are coupling strongly. shell, plate, shallow arch, membrane) have been widely used in unmanned air vehicles (UAVs) and micro-air vehicles (MAVs) (Shyy et al., 2010, Shyy et al., 1999, Yu et al., 2013).
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