Impact of frictional structural nonlinearity in the presence of negative aerodynamic damping

The focus of this paper is on providing a first validation of the possible role of friction as a stabilization mechanism in post-flutter limit cycle oscillations (LCO). To this end, four structural lumped mass models exhibiting both friction and a negative dashpot modeling the unstable aerodynamics were considered and their response computed by numerical simulation, through an exact formulation, and by the harmonic balance method. Continuous slip and stick slip LCO motions were indeed obtained in a broad range of negative damping ratios thereby demonstrating the stabilization potential of friction. A detailed analysis of the LCO responses in the time and frequency domains was performed to provide a more in depth phenomenological perspective. Finally, a comparison of the prediction strategies validated the use of both the exact formulation and the harmonic balance method for this class of problems.