Effect of Nonlinear Energy Sink on Aeroelasticity of High Aspect Ratio Wings

Abstract In this paper, the effectiveness of nonlinear energy sinks on enhancing aeroelastic stability and post-instability response of aircraft wings is investigated. The wing has two degrees of freedom in bending and torsion, and is modelled using a 3rd-order nonlinear beam model. A Nonlinear Energy Sink (NES) absorber is embedded inside the wing. The NES mass is connected to the wing spar through a linear damper and nonlinear spring with a cubic stiffness nonlinearity. The wing aerodynamic loads are simulated using a quasi-steady model with a cubic stall nonlinearity. The coupled aeroelastic equations for the wing and damper are discretized using Galerkin’s method. The coupled aeroelastic equations are then transformed to state space and integrated numerically to resolve the bending and torsional response of the wing. The impact of the NES on the flutter response of the wing is then investigated across a range of flow speeds pre- and post-flutter. The results demonstrate that the NES is most effective in reducing the Limit Cycle Oscillation (LCO) amplitude when in the immediate post-flutter region. This effectiveness decreases as the flow speed increases with it, dropping from 33% at 195 ft/s to just 3% at 220 ft/s. The performance of the NES is compared to a linear tuned mass damper with the results indicating the nonlinear device is more effective across the whole range of flow speeds.