摘要：Transverse injection into supersonic flow after rearward-facing step combines a simple way to improve mixing and flameholding in Scramjet engines. In this essay, large-eddy simulation, NPLS, and PIV techniques are applied to study the flow characteristics of a sonic jet with different flow rates after rearward-facing step interacting with supersonic turbulent flow. Results show that since a big recirculation zone is generated by rearward-facing step before the jet, the barrel shock in the windward side is not so obviously compressed so that jet fluid enters the recirculation zone providing a flammable region for ignition and combustion stabilization. Besides, jet fluid bypassing the Mach disk comes directly into interaction with the turbulent boundary layer separated from the rearward-facing step to enhance vortices development in the further downstream. The comparisons of average boundaries abstracted from NPLS images with empirical penetration height equations show that mixing enhancement of transverse injection into supersonic flow after rearward-facing step has a close relationship with the jet to free-stream momentum. In small jet to free-stream momentum case, the mixing shear layer grows mainly in the near field of the jet, while in big jet to free-stream momentum case, the growth of the mixing shear layer could extend to the far-field wake flow zone of the transverse jet.
