Aeroelastic responses of elastically suspended airfoil systems in transonic buffeting flows

Navier-Stokes simulations are performed to determine the responses of a single-degree-of-freedom pitch airfoil system, as well as those of a two-degree-of-freedom pitch-and-heave system, in buffeting flows. The buffeting flow exhibits shock-wave oscillations of a unique frequency that occurs for some combinations of mean flow angle of attack and transonic Mach numbers. It was found that frequency lock-in may occur, when the frequency of the elastic system is close to the buffet frequency, and the amplitude of the elastic oscillation is above some threshold. Following frequency lock-in, the system response rapidly increases until reaching a limit-cycle oscillation. Synchronization of the transonic aerodynamic buffet phenomenon and the structural elastic modes provides a physical mechanism that leads to a limit-cycle oscillation, as observed in the current computational study.