Characteristics of enhanced mixing induced by plate jet actuation in supersonic flow

Abstract

The fast and efficient mixing of fuel and oxidizers under supersonic conditions is of great importance for improving the performance of scramjet engines. The mixing process in the inner flow of a scramjet combustor is heavily inhibited by compressibility effects. In this paper, the novel strategy of plate jet actuation is proposed, and its effects on mixing augmentation are analyzed by employing numerical programs developed in-house. The fine vortex structures induced by the plate jet actuation are well captured, and the dynamic behaviors of newly observed T-shaped structures are analyzed in detail. It is found that in plate jet actuation flow, Kelvin–Helmholtz (K–H) vortices induced by K–H instability coexist with T-shaped structures induced by jet actuation instability. The interaction of adjacent T-shaped structures leads to the distortion and breakup of large-scale structures, which can obviously improve the interfaces of upper and lower streams. The distribution of the turbulence intensity along the streamwise direction suggests that with the introduction of plate jet actuation, more intense fluctuations occur in the flow. The growth process of mixing layer thickness indicates that with plate jet actuation, a sharp increase in mixing thickness can be achieved in the near flow field. The results of structural topology analysis show that upper plate jet actuation can produce structures with larger sizes, and the distortion and penetration process of these structures can entrain more upper and lower streams into the mixing region. It is suggested that the present proposed strategy is a good candidate for mixing enhancement with the application of scramjet combustors.