High-Fidelity Flutter Prediction of Aspect Ratio 13.5 Flexible Wing Wind Tunnel Model

This paper presents a high-fidelity computational approach for flutter prediction of an aspect ratio 13.5 Common Research Model wind tunnel model tested in the NASA Langley Research Center Transonic Dynamics Tunnel. A computationally efficient approach is proposed using a multi-sine, multi-mode, frequency-shifted bowed square wave train excitation to efficiently excite multiple structural dynamic modes over a wide frequency range with a single unsteady Reynolds-averaged Navier-Stokes computational fluid dynamics simulation in FUN3D. The generalized aerodynamic forces are extracted as a function of the reduced frequency. Reduced-order modeling is performed via Roger's rational function approximation to obtain a frequency-domain approximation of the generalized aerodynamic forces computed by FUN3D. By converting the frequency-domain approximation into a time-domain state-space realization, an eigenvalue analysis is conducted to compute the frequencies and damping ratios as functions of the tunnel dynamic pressure. The predicted flutter boundary is used as a guide to determine an allowable test envelope for the ensuing flutter suppression control experiment. This method aims to provide a more efficient and accurate prediction of flutter characteristics by capturing complex mode interactions. The predicted flutter boundary is compared to that predicted by NASTRAN flutter solution. Comparison of the flutter prediction to limited wind tunnel test data at Mach 0.65 is made to validate the flutter solution.