Study of a Hypersonic Far Wake Using Laser Diagnostics

In this study, acetone molecular tagging velocimetry (MTV) was employed to measure velocity in the far wake of both a free-flight and strut-mounted sphere in the Mach 7 wind tunnel facility at the University of Texas at San Antonio. The far wake, defined here as the region beginning approximately two body diameters downstream of the sphere, was characterized using MTV to obtain a two-dimensional velocity field and velocity fluctuations. For the free-flight case, the 2D velocity map showed turbulent structures forming after the neck of the inner far wake, where velocities were measured to be ~100 m/s. Outside the inner turbulent wake velocities increased to ~600 m/s. For the strut-mounted case, all profiles converged to a velocity of 470 m/s, corresponding to a shock observed in the schlieren images, likely originating from the SWBLI formed between the model and the strut. Additionally, planar laser scattering (PLS) of condensed carbon dioxide particles was used to visualize the wake structures in the spanwise direction of the spherical model in free-flight. Spanwise PLS effectively showed cold flow regions where the bow shock is formed in the outer wake, as well as hot flow regions within the inner wake.