The oblique shock/vortex interaction (OSVI) is numerically investigated based on the large-eddy simulation method. A Mach interaction between separated shock and incident shock can be found when the pressure at recirculation region reaches a certain level. Based on the idea of spatial-temporal correlation, which considers the three-dimensional steady interaction as a two-dimensional unsteady problem, a qualitive analysis is conducted to explain complicated three-dimensional shock structures. The interaction can be regarded as a combination of the following events: the interaction between circular shock and normal shock, the reflection of shock wave on subsonic interface, and the interaction between secondary circular shock and other shock structures. Though the original vortex has broken down, a pair of the streamwise vortices can be observed in the downstream flow field, the formation of which is associated with the split of recirculation region. Moreover, the recirculation region is found to act as a solid body, which means that the flow angle along splitting curve can reflect the splitting speed. Three stages can be identified according to the change process of flow angle along splitting curve, which are rapid growth, linear growth and decrease stages. Inspired by the studies on shock-induced boundary layer separation, the flow filed of strong OSVI with regular interaction is modeled to predict the initial flow angle of splitting point which is the foundation of the study on other stages. The interaction type between separated shock and incident shock can also be judged according to this approach.

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Structural characteristics of the strong interaction between oblique shock wave and streamwise vortex are experimentally investigated based on the Nanoparticle-based Planar Laser Scattering (NPLS) technology. Fine structures of reorganized vortices and helical structures are first recorded in experimental visualization. For the case with the strongest shock wave, a catastrophe process occurs due to the change of breakdown type, which gives birth to abundant small-scales vortical structures. Fractal and feature analyses indicate that the turbulent mixing dramatically increases after the interaction, especially for the case with spiral breakdown.

In accordance with high-speed schlieren results, the flow instabilities in the subsonic–supersonic mixing layer with a convective Mach number of 0.19 are investigated in detail. In the incipient stage of the mixing layer, wave structures caused by the pressure gradient affect the evolution of the Kelvin–Helmholtz vortexes. The dynamic mode decomposition (DMD) analysis reveals that the pressure gradient from the subsonic side to the supersonic side promotes flow instability. At this time, the Kelvin–Helmholtz vortexes mode is found to be dominant. A high temporal resolution is proven to play an important role in the DMD analysis to capture high-frequency modes.

Supersonic boundary layer transition induced by a streamwise vortex is experimentally investigated based on the Nanoparticle-based Planar Laser Scattering (NPLS) technology, with an inflow Mach number of 2.7 and a unit Reynolds number of 8.79×106 m-1. Though the vortex is outside the boundary layer, it results in obvious difference of transition position along spanwise direction. On the up-wash side, transition to turbulence is completed in advance compared to the vortex-free case, and transition position moves more upstream as the vortex approaches the wall. Conversely, the transition process on down-wash side is inhibited. The promotion and inhibition effects on transition are found to be induced by the influence of vortex on streak density.