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

Large-amplitudeself-sustaining periodic oscillationshavebeen observed in an unforced pitch-axis single-degreeof-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� ection) is varied quasi statically and the steady-state response of the system recorded. An innovative strategy based on these bifurcation diagramsis then used to identify amathematical 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� ections.