Time/Frequency Analysis of the Flutter of the Flexible HSCT Semispan Model

Time/frequency analysis of fluctuations measured by pressure taps and strain gages in the experimental studies of the Flexible Semispan Model of High Speed Civil Transport wing configuration is performed. The interest is in determining the coupling between the aerodynamic loadings and structural motions that lead to the hard flutter conditions and loss of the model. The results show that, away from the hard flutter point, the aerodynamic loadings at all pressure taps near the wing tip and the structural motions contained the same frequency components. On the other hand, in the flow conditions leading to the hard flutter, the frequency content of the pressure fluctuations near the leading and trailing edges varied significantly. This lead to contribution over two frequency ranges to the structural motions. The ratio of these ranges was near 2 to 1 which suggests the possibility of nonlinear structural coupling.