Application of High-Speed Acetone-PLIF to a Supersonic Jet in Hypersonic Crossflow

High-speed acetone planar laser-induced fluorescence (PLIF) was applied to an underexpanded, supersonic jet transversely injected from a flat plate into a hypersonic air crossflow. The experiments were conducted in the UTSA Mach 7.2 Ludwieg tube wind tunnel with a freestream unit Reynolds number of 37 ×10^6 m-1. The supersonic nozzle had a design Mach number of approximately 3 and jet fluid was comprised of nitrogen (N2) seeded with acetone vapor. The jet was characterized through visualization of the Mach disk height in quiescent conditions using schlieren visualization. Schlieren visualization was also used to characterize the flat plate without jet injection. PLIF was used to visualize the development of coherent structures in the jet-in-crossflow shear layer with acquisition rates of 10 kHz and 200 kHz. The 10 kHz case provided high signal-to-noise ratio (SNR) images of the shear layer morphology, while the 200 kHz case allowed time-resolved visualization of dynamics including shear layer roll-up and barrel shock oscillations. Large coherent structures visualized in the shear layer using PLIF are compared to the deformations of the bow shock and barrel shock observed in the schlieren imagery.