Structural Dynamic Analysis of a Flexible Wing Through Distributed Bleed Flow Control

Controlled flow-structure interactions on a flexible 3-D wing model are employed to induce desired adaptive aeroelastic characteristics. The coupling between regulated aerodynamic loads and aeroelastic properties is explored using controlled distributed bleed actuation that is effected by the pressure differences between the model's pressure and suction surfaces. Wind tunnel experiments are conducted to evaluate the transient response of the wing to controlled load perturbations when bleed ports are opened and closed according to a square-wave schedule. The recorded displacements are employed for the estimation of natural frequencies and damping ratios associated with the first fundamental modes, which are estimated by estimating the logarithmic decrement during transients. Furthermore, periodic excitation to the wing is investigated when the bleed actuation is applied for fundamental periods of actuation that are below, at, or above the first fundamental bending mode and the aeroelastic properties obtained from the transient response are compared with those corresponding to the time-stationary response in the absence and presence of actuation. The present investigations enable estimation of the apparent, bleed-induced changes in the wing's characteristic stiffness, damping, and natural frequency, which provide insights into the aeroelastic performance of the wing with bleed.