Measurements of mixing layers and vortex structures of the strut-induced flow in a scramjet combustor with PIV and POD

The organization of the flow field in a scramjet is of great significance in achieving stable combustion in supersonic flow. Experimental investigation of the strut-induced flow in a scramjet is conducted with particle image velocimetry (PIV) measurement. The central wakes along with two outer free streams can be observed in the instantaneous velocity fields. Then the calculated vorticity shows a similar distribution with the mixing layers in the single-shot image, suggesting the mixing layers a preliminary assessment of the flow. Proper orthogonal decomposition (POD) of snapshots reveals several features beneficial for flame stabilization in the strut-induced flow, including the reverse flow, central large-scale vortex structures and the vortex structures in the mixing layers. Moreover, by comparison it is found that a significant asymmetry of strut-induced flow would compress the low-speed region and weaken the large-scale vortex structure which would present a challenge to achieve flame establishment. The research contributes to a profound understanding of strut-induced flow which may be useful for engineering design and optimization.