Numerical Study on Turbulent Structure of Transverse Jet into Supersonic Flow

Abstract

We investigated the three-dimensional turbulent structure of a transverse air jet injected into a Mach 1.9 supersonic crossflow and evaluated the jet mixing state using a large-eddy simulation (LES). A grid sensitivity study and detailed comparisons with acetone planer laser-induced fluorescence data validated our LES. The LES results reproduced the injectant mixing field, not only in the averaged distribution of the injectant concentration, but also in the large-scale turbulent features. Large-scale vortices in the windward side of the jet plume caused large protrusions of injectant and were the main cause of the turbulent diffusion of injectant toward the crossflow in the near-field. The windward large-scale vortex structure consisted of a string of hairpin-like vortices meandering along the jet trajectory. The head of these hairpin vortices tilted toward the upstream and upward directions. The instantaneous combustible injectant mass flux was evaluated by assuming the injectant air to be ethylene. A large amount of combustible injectant existed inside the large-scale protrusions induced by the windward large-scale vortex structure. The combustible injectant mass flow rate passing through the cross-section has substantial fluctuations over time, mainly due to the intermittent appearance of the windward largescale vortices.