Abstract:

The transonic buffet is an aircraft wing oscillation arising due to the interaction between the supersonic bubble and separation layer. A sustained buffet can damage the aircraft and as a result, it must be carefully taken into account during the aircraft design. We study the buffet that appears when the angle of attack (AoA) is increased. The onset of the buffet can be explained by Hopf bifurcation. We generated simulations for different AoA using the time-accurate Reynolds-Averaged Navier–Stokes solver. The described approach applies the dynamic mode decomposition (DMD) to extract flow components responsible for the buffet onset. We applied a DMD with a sliding window to track the onset of buffeting in order to adjust to non-steady-state data during the flow transient. By comparing dominant DMD mode profiles across different AoA we identify ranges of AoA values corresponding to the no oscillation, pre-buffeting, buffeting, and post-buffeting regions. We demonstrate that the described method performs well across flight conditions and airfoil shapes.

Keywords:

Transonic buffet, Hopf bifurcation, Sliding window DMD