The flow features of Transverse Jets In Supersonic Crossflow

Abstract

The aim of this paper is to present an experimental investigation of Transverse Jets In Supersonic Crossflow (TJISC) using flow visualization. Air, argon, and helium sonic under-expanded jets transversely injected into a Mach 3 supersonic crossflow through a turbulent boundary layer were visualized using both a conventional z-type and a focusing high-speed schlieren. The jet-to-crossflow momentum flux ratios J for the air cases were 1.17-3.85, and J were 1.21-3.89 for the argon and helium cases. The instantaneous schlieren images reveal quasi-periodically shedding vortices generated in the shear layer owing to the Kelvin-Helmholtz (K-H) instability. These images demonstrate an unsteady interaction generated between the shear layer vortices and the adjacent shock structures via compression waves. This interaction results in a time-varying deformation of the λ shock. A series of moving shocks propagating along the shear layer near the bow shock are identified in the helium TJISC. These moving shocks are generated as the convection velocity of the helium fluid in the convective frame is supersonic with respect to the surrounding flow. The penetration depth of the TJISC is identified based on the time-dependent instantaneous schlieren image series. These moving shocks lead to discontinuous pressure distributions, interact with the bow shock, and enhance the unsteadiness of the flow field. The crossflow parameters (pressure, velocity, temperature, momentum) downstream of the moving shocks are altered consequently. The penetration depth of the helium TJISC is slightly increased compare with the air and argon cases due to the altered effective momentum flux ratio induced by these additional moving shocks.