applied sciences  
A Mixing Process Influenced by Wall Jet-Induced Shock Waves in Supersonic Flow  
[PERSON], [PERSON], [PERSON] and [PERSON],*  
1 Science and Technology on Scramjet Laboratory, National University of Defense Technology, Changsha 410073, China 1  
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mixing time and the influence of a compression effect [2; 3; 4], it is urgent to adopt mixing enhancement strategies to improve mixing efficiency. In order to realize mixing enhancement of supersonic flow, researchers worldwide have put forward a variety of mixing enhancement techniques, which can be divided into passive active methods. The passive mixing method perturbs the mixing layer by changing the configuration of the middle partition plate of the mixing layer or adding a disturbance device to speed up the mixing. Our previous work comprehensively reviewed passive strategies proposed by investigators to promote mixing [5]. Typical passive mixing enhancement measures include: lobe mixer [6], slope device [7], cavity [8; 9], strut [10], and so on. A fact that cannot be ignored is that due to the introduction of a passive device, the inherent defect, including non-ignorable flow loss [11], limits the wide usage of these techniques. Active mixing enhancement methods are to t external energy into the mixing layer by introducing external excitation, and mixing enhancement is achieved by the regulation of the mixing layer. Typical active mixing enhancement strategies include acoustic excitation [12], plasma magnetic fluid excitation [13], blowing and suction [14], reflux device [15], vibration device [16; 17], etc. The work conducted by [PERSON] [18] et al. indicated that in the low-speed shear layer, sinusoidal excitation can promote earlier instability of the flow, and the rolled-up K-H structures can notably increase the mixing level. Whereas, in supersonic conditions, the effect of an electromagnetic flap is negligible. Therefore, it can be concluded that the defect of both active and passive strategies calls for newer methods to realize mixing enhancement. It is worth noting that as the inherent flow structures in the confined supersonic mixing layer flow, shock waves [19] and their dynamic behaviors can significantly influence the flow evolution process. Specifically, the interaction between shock waves induced by a wedge shock generator and the mixing layer can notably affect the K-H vortex development. [PERSON] [20] obtained the first experimental visualization results and found that shock wave induced by a wedge generator contributed to mixing enhancement. [PERSON] and [PERSON] [21] used direct numerical simulation (DNS) to research the effect of shock waves on the mixing layer and found that the influence of a shock wave on the mixing layer is very local and the installation should be set as early in the upstream as possible to short the initial mixing distance. [PERSON] [22] claimed that the growth rate of the mixing layer increased slightly under the impingement of shock, but it returned to the original value within a short distance downstream.