The effect of structural characteristics on frequency lock-in in transonic buffeting flows

Transonic buffet is a phenomenon that substantially limits the flight envelope of commercial aircraft. The oscillation of the shock wave on the wing surface leads to strong alternating loads. Given particular structural characteristics, fluid-structural coupling can occur (buffeting) and result in severe structural damage. As numerical work has shown, the structural parameters can hereby have a significant effect on the onset of shock oscillations as well as on the typology of the fluid-structure interaction (classical structural excitation, modal veering and frequency lock-in). This work experimentally investigates the those findings on an elastic wing model based on the supercritical OAT15A airfoil by varying the structural mass ratios from 284 to 322 and the pitch-to-clean-buffet frequency ratios from 0.9 to 1.6 at a Mach number of 0.74. The experimental results confirm the numerical findings regarding the effect of natural pitch frequency on the oscillation amplitude, whereas a more substantial effect of the mass ratio on the resulting pitching amplitude has been observed.