Aeroelastic Interactions of a Supercritical Aerofoil in the Presence of Transonic Shock Buffet

摘要

Within a small region of flight conditions in a transonic flow, shock-wave/boundary-layer interactions give rise to large amplitude, self-sustained shock oscillations that are detrimental to both platform handling quality and structural fatigue life. In this study, the aeroelastic interactions between this transonic buffet instability and a spring suspended supercritical aerofoil are investigated by means of Reynolds-averaged Navier-Stokes simulation. The computational method is validated against static aerofoil data, from which single degree-of-freedom pitching and heaving simulations are performed for a range of sectional mass ratios. The results show that with a decrease in mass ratio, the structural and aerodynamic responses are amplified. This amplification is particularly pertinent to the pitching aerofoil at low sectional masses, where bifurcation in the aeroelastic system yields a topological change in buffeting flow field. Additionally, with structural eigenfrequencies in close proximity to the frequency of shock oscillation, sychronisation of the buffeting and structural modes occurs. This so called lock-in phenomenon has been previously identified and provides a mechanism for Limit Cycle Oscillations in aircraft structures. From this study, it is suggested that in a spring suspended aerofoil system, the onset of such lock-in phenomena is not heavily influenced by the sectional mass ratio, but rather, critically dependent on the relative structural and aerodynamic frequencies.