Under the background of dual combustor ramjet (DCR), a numerical investigation of supersonic mixing layer was launched, focused on the mixing enhancement method of applying baffles with different geometric configurations. Large eddy simulation with high order schemes, containing a fifth-order hybrid WENO compact scheme for the convective flux and sixth-order compact one for the viscous flux, was utilized to numerically study the development of the supersonic mixing layer. The supersonic cavity flow was simulated and the cavity configuration could influence the mixing characteristics, since the impingement process of large scale structures formed inside the cavity could raise the vorticity and promote the mixing. The effect of baffle’s configurations on the mixing process was analyzed by comparing the flow properties, mixing efficiency, and total pressure loss. The baffle could induce large scale vortexes, promote the mixing layer to lose its stability easily, and then lead to the mixing efficiency enhancement. However, the baffle could increase the total pressure loss. The present investigation could provide guidance for applying new passive mixing enhancement methods for the supersonic mixing. 1. Introduction High-speed flight vehicles call for new type propulsion system and scramjet has attracted researchers’ attention to focus on this technique [1]. In order to adapt to the requirements of hypersonic vehicle at different flight Mach numbers, the dual combustor ramjet (DCR) was proposed, which was more superior to the conventional dual mode ramjet. The advantages include without fuel pretreatment, ignition and combustion stability, low Mach number launch, without mode conversion, and so on [2–4]. However, the superiority could result in complexity of the structure of engine and hence complicate internal flow and combustion characteristics. The combustion must occur quickly and requires fuel mix rapidly with oxidizer. In addition, the well mixing of fuel-rich gas from subsonic combustor with supersonic flow could achieve the advantages of DCR, and then the second combustion in supersonic combustor could proceed effectively. However, it is difficult to achieve the fully mixing of high-speed flows. Thus, the mixing enhancement measures to organize stable and efficient combustion in DCR are of importance. The research on the mechanism of mixing layer contributes to perceive the flow stability, transition from laminar to turbulent and turbulence phenomena, finding the factors affecting the mixing efficiency. Initially, the study of the mixing layer was
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