Combining Viscoelastic Damping and Nonlinearities to Widen the Operational Speed Range of Flutter Energy Harvesting Available to Purchase

We propose using viscoelastic damping with combined hardening and free-play structural nonlinearities to enhance energy harvesting performance and control vibration in a pitch and plunge airfoil with piezoelectric transduction. Numerical simulations are performed by directly integrating the equation of motion in the time domain under unsteady aerodynamic load. In addition, a fractional derivative model efficiently accounts for the behavior of the viscoelastic material. This study analyzes the effect of each structural nonlinearity and identifies a good condition for harvesting in terms of cut-in speed and operational speed range. For this condition, the viscoelastic damper in pitch can further reduce the cut-in speed by 13%, slightly increase the harvested power, and help reduce the dynamical complexity of the system response. In turn, the viscoelastic damper in the plunge degree-of-freedom can control the vibration amplitude at postcritical flow speeds, increasing the operational speed range up to 28% and the power up to two orders of magnitude in some cases. Viscoelastic damping maintains a favorable harvesting condition for temperature variations from $10∘C$ to $35∘C$⁠.