Comparative study on aeroelastic characteristics of a cropped delta wing before and after vortex breakdown

Aeroelastic analysis at high angles of attack is an attractive and complicated research subject in modern aircraft design. By using the Navier-Stokes(N-S) equations coupled with structural motion equations, an aeroelastic analysis of a 70° cropped delta wing before and after vortex breakdown in the time-domain is performed in a state-space. It is shown that the unsteady fluctuation characteristics of the flow become highly obvious after the vortex breakdown, which exert a significant impact on the aeroelastic characteristics of the wing. Before the vortex breakdown, the aeroelastic instability presents itself as just a simple flutter. However, after the vortex breakdown, the aeroelastic phenomenon may be neither a simple flutter, nor a simple buffet induced by the external excitation loads on the wing, but a complex state including both flutter and buffet. As the angle of attack increases, the vortex breakdown location moves forward, and the external excitation loads due to the vortex breakdown rise. The influence of buffet thus increases, and the aeroelastic characteristics become a more obvious phenomenon involving flutter and buffet. Besides, from the analysis of the power spectra density (PSD), it is also found that the fluctuating loads on the wing rise and the frequency of the peak on the PSD decreases as the angle of attack increases.