Experimental analysis and modelling of limit cycles in a dynamic wind tunnel rig

Large-amplitude self-sustaining periodic oscillations have been observed in an unforced pitch-axis single-degree-of- freedom dynamic wind-tunnel rig. These limit-cycle oscillations and the associated bifurcations are caused by aerodynamic phenomena and have been studied by constructing experimental bifurcation diagrams, where a system parameter (horizontal tailplane deflection) 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 mathematical model of the rig aerodynamics over a wide operating region. Good agreement is shown between numerical simulations of the theoreticalmodeland experimental time histories over a large range of angle-of-attackand tailplane deflections.