Confinement and Heat-Release Effects on the Mixing Region Development in a Scramjet

This paper presents a numerical investigation of mixing in supersonic flows using the hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation. Three configurations are comparatively studied to investigate the effects of confinement and heat release on the mixing: a nonreacting case without confinement, a nonreacting case with confinement, and a reacting case with confinement. First, the mixing region area is quantified and its development is characterized. Subsequently, the deformation and rotation of fluid are analyzed to illustrate the impacts of shocks and combustion on the mixing region development. The transport of vorticity is further discussed to explore the driving mechanism of mixing in different cases. The results show that the impingement of oblique shocks on the mixing region reduces its area due to compression but enhances the subsequent mixing by promoting vorticity via the dilatation and baroclinic torque effects. This leads to a wavelike pattern for the development of the mixing region. Heat release expands the mixing region and decreases vorticity in the upstream, where high heat-release rates are observed. Downstream, combustion products mix with air, and only weak heat release takes place. In that region, the baroclinic torque effect becomes dominant and results in higher vorticity as compared to the nonreacting case.