The vortex-lift waverider presents great potentiality in the design of wide-speed-range hypersonic vehicles. However, its constrained lift characteristics, resulting from vortex breakdown at low-speed, high-angle-of-attack (AOA) conditions, restrict its capability for horizontal takeoff and landing. To address this problem, the lift enhancement mechanism during pitching oscillation under low-speed high-AOA conditions is investigated in this study using the delayed detached eddy simulation (DDES) method. First, the static lift characteristic of the vortex-lift waverider is discussed. A lift concave region is observed at Formula: see text AOA in the static lift line because of the leading-edge vortex breakdown. Subsequently, the numerical simulations of pitching oscillations are performed. The results reveal that the pitching oscillation can delay the vortex breakdown due to the hysteresis characteristics, which remarkably improves the lift at elevated AOA. Furthermore, the lift characteristic during pitching oscillation at varying reduced frequencies is also investigated. As the reduced frequency increases, the hysteresis of vortices is enhanced, and the suppression effect of the pitching oscillation on vortex breakdown becomes more pronounced. Meanwhile, the maximum lift within the oscillation period increases synchronously. In case the reduced frequency is greater than 0.18, the maximum lift within the oscillation period tends to be stable, increasing by 19% compared to the static case.
Qu et al. (Sun,) studied this question.