Experimental bifurcation analysis of a wing profile

The prediction of flutter instabilities is very critical in aeroelstic wing design, as it limits the aircraft operational envelope. Aeroelastic structures that have nonlinear characteristics, as in highly flexible wings, can exhibit limit cycle oscillations in the vicinity of the flutter boundary. However, comprehensive characterization of these nonlinear oscillations can be challenging without a well established nonlinear mathematical or numerical model. In the present paper,control-based continuation (CBC) technique is used to characterize the nonlinear oscillatory dynamics of a physical aeroelastic system undergoing pre and post flutter oscillations, without the use of a mathematical model. The aeroelastic system was represented by a two-dimensional wing with pitch and heave degrees of freedom, tested in the low turbulence wind tunnel of the University of Bristol. The aim of this research is to demonstrate the capability of the CBC technique to trace unstable periodic behavior through stabilizing unstable limit cycle oscillations. The results allowed to produce a full bifurcation diagram for a fluttering wing profile, despite the noisy turbulent flow environment of the wind tunnel.