Experimental Analysis and Modeling of Limit Cycles in a Dynamic Wind-Tunnel Rig

Large-a mplitude self-sustaining periodic oscillations have been observed in an unforced pitch-axis single-degreeof-freedom dynamic wind-tunnel rig. These limit-cycle oscillations and the associated bifurcations are caused by a erodynamic phenomena and have been studied by constructing experimental bifurcation diagrams, where a system parameter (horizontal tailplane deection) is varied quasi statically and the steady-state response of the system recorded. An innovative strategy based on these bifurcation diagrams is then used to identify a mathematicalmodel of the rig aerodynamics over a wide operating region. Good agreement is shown between numerical simulations of the theoretical model and experimental time histories over a large range of angle-of-attack and tailplane deections.