An original variational formulation is developed for the inverse problem of reconstructing full-field structural displacement and pressure distribution of membrane wings subjected to steady loads from membrane strain distribution. A direct solution approach in cosimulation with fluid-dynamics solvers is also presented. Moving least squares are used to smooth and remap surface strain measurements, estimated from digital image correlation, as needed by the inverse solution meshing. The same approach is used to map the structural and fluid interface kinematics and loads during the fluid-structure cosimulation. Both the direct and the inverse analyses are validated by comparing the direct predictions and the reconstructed deformations with experimental data for prestressed rectangular membranes subjectedtostatic and unsteady loads. The load distributions reconstructed using the inverse analysis are compared with the corresponding loads obtained using the direct analysis. The inverse analysis runs on standard off-the-shelf PCs and can be implemented in real time, providing load-distribution estimates at a rate in the order of tens of data sets per second

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Flow separation followed by aerodynamic stall limits the operation of aircraft. Expanding the flight envelope of aircraft has been a goal of aerodynamicists for decades. This work presents findings from tests in the Oregon State University wind tunnel investigating the effectiveness of a passively actuated suction-surface flap on membrane wings. Experiments were conducted on a rigid plate and membrane wings with and without a pop-up flap. All wings had an aspect ratio of 2, while membrane pre-strain and Reynolds number were varied. An increase in lift at stall was observed for all testing conditions with flap deployment. The observed average increase in maximum lift varied from 5% to 15% for different test conditions. The variation in flap effectiveness is compared to membrane pre-strain, Reynolds number, and wing camber. A quadratic relationship between modelled camber and flap effectiveness is observed, and an optimal level of membrane camber is found to maximise flap effectiveness.

Thin structural components characterize a broad class of Micro-Aerial Vehicles (MAV). This work presents an original approach for the determination of transverse load distribution based on distributed strain measurements. A variational formulation is developed for the inverse problem of the reconstruction of full-field structural displacement of membrane wings subjected to static and unsteady loads. Surface strain measurements are estimated from Digital Image Correlation (DIC). Moving Least Squares are used to smooth and remap measurements as needed by the inverse solution meshing, and to map the structural and fluid interface kinematics and loads during the fluid-structure co-simulation. The inverse analysis is verified by reconstructing the deformed solution obtained with an analogous direct formulation, based on nonlinear membrane structural analysis implemented in a general-purpose multibody solver and tightly coupled in co-simulation with a CFD solver. The direct analysis is performed on a different mesh and subsequently re-sampled. Both the direct and the inverse analyses are validated by comparing the direct predictions and the reconstructed deformations with experimental data for prestressed rectangular membranes subjected to static and unsteady loads. The reconstructed load distributions are compared with the corresponding ones obtained using the direct analysis

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