Design and experimental tests of a flexible wing of high-aspect ratio for investigating flutter mechanisms

ifasd2024 Tracking Number 160

Increasing the aspect ratio of wings may have beneficial effects in terms of aerodynamics, such as a higher lift on drag ratio. However, High-Aspect-Ratio Wings (HARW) also have a natural flexibility that can make them prone to aeroelastic instabilities for specific flight conditions. Unfortunately, computing the flutter-free domains of these HARWs is tricky due to the onset of nonlinear phenomena present for high amplitudes of wing deflections. In that context, this paper presents the study of a taut-strip flexible wing model, particularly designed to experience flutter in a wind tunnel at low-to-moderate Reynolds numbers. The objective was to keep the structural complexity as low as possible, while exhibiting fluid-structure interactions typically observed for these types of wings. The choice of structural design was based on the numerical prediction coming from a low-order aeroelastic model combining beam theory and simplified aerodynamics. The choice of structural design was based on the numerical prediction coming from a linear low-order aeroelastic model combining beam theory and simplified aerodynamics. Thanks to dynamical tests in laboratory, structural parameters (inertia, stiffness, damping coefficients) were used to update the numerical model. Using this linear model, a flutter involving a coupling between the 2nd bending mode and the 1st torsion mode was expected in the velocity range of the wind tunnel. Wind tunnel tests however show an earlier flutter bifurcation involving flapwise, chordwise and torsion motions, for which the route to flutter and post-critical limit-cycle oscillations have been measured by non-contact techniques.