Aeroelastic wind-tunnel test for aerodynamic uncertainty model validation

A half model of a scaled-down aircraft is designed and tested in the wind tunnel to validate the mathematical model of uncertainty for unsteady pressure coefficients in the frequency domain. In the wind-tunnel test a step-swept test was conducted to obtain the frequency response function. Then a time-domain response test was performed with turbulence excitation to identify the aircraft's on-line poles. Based on the tested frequency response function for the on-line poles the structured singular value (μ) method was applied to determine the aerodynamic uncertainty level. Finally, the widely used μ analysis method was employed to compute the worst-case flutter boundary, and the result was compared with the experimental flutter velocity. The experimental flutter velocity (30.5 m/s) is in the range of the predicted robust flutter boundary (28.5 m/s) in which parameter uncertainties were taken into account in the numerical model. Experimental results validate that the uncertainty quantification theoretical frameworks incorporating experimental data can estimate the proper aerodynamic uncertainty level and predict a safe flutter boundary. The present results suggest that the time-response validation theoretical framework is more advantageous in robust stability analysis than the one based upon the frequency response function.