Energy harvesting and passive mitigation from flutter via rotary nonlinear energy sink

Abstract

Nonlinear Energy Sinks (NES) are passive vibration absorbers that transfer energy to a nonlinearly-attached secondary mass for passive dissipation at broad excitation ranges. Aeroelastic flutter is a potential application of NES passive control once it presents complex, self-excited, and self-sustained potentially harmful high-amplitude oscillations. When combined with a transducer mechanism, NES devices can perform simultaneous passive control and electricity generation, reusing otherwise dissipated structural energy. This work proposes an apparatus comprising a rotary Nonlinear Energy Sink coupled with an energy harvester (RNES-EH) to an aeroelastic typical section. A two-dof airfoil subjected to an unsteady aerodynamic load model is considered. A pitching hardening nonlinearity is adopted, inducing limit cycle oscillations in the post-critical response. The RNES-EH is introduced at the airfoil chord, and the aeroelastic electromechanical equations of motion are derived. Numeric characterization is performed on the basis of the behavior of the bifurcation and suppression regimes of the system for a reference device. A performance index is introduced to balance energy harvesting and vibration reduction. Parametric bifurcation analysis is carried out to determine the influence of parameter design on vibration mitigation and electricity generation. The device is reported to generate electric power without disrupting the suppression performance. Mechanically, a low-radius and high-mass device close to the leading edge and with some damping is required for optimal suppression, although performance is limited due to subcritical behavior. Optimal load resistance is determined for maximum electricity extraction. The results show that the concept is promising and viable for many aeroelastic and fluid–structure interaction problems.