Nonlinear flap for passive flutter control of bidimensional wing

A solution for passive aeroelastic control is presented and tested experimentally on a bidimensional wing setup. The solution consists of a flap integrated in the wing which acts as a secondary mass damper and absorbs energy when aeroelastic instability is encountered. This device is passive, which makes it safe in emergency cases and adds little mass to the system in the fundamental case presented in this paper. If installed on actual aircraft wings, the flap-NES would not substitute but coexist with classic active control methods, adding virtually zero mass to the existing system. Using a flap placed in the airflow enables the control system to benefit from aerodynamic damping with a behavior dependent on wind speed. The device can either have a linear or nonlinear stiffness. It is shown that both options absorb energy from the main system, that is, the wing. The flap acts as a TMD (tuned mass damper) in the linear case and as an NES (nonlinear energy sink) in the nonlinear case. The nonlinear solution not only absorbs more energy at given wind speed but it also is a more suited solution as the damper follows the wind speed dependent frequencies due to its nonlinear feature. In this work, the flap-TMD and the flap-NES are tested experimentally on a bidimensional wing which presents classic flutter.