Tunnel Noise Effects on Hypersonic Cylinder-Induced Transitional Shock-Wave/Boundary-Layer Interactions

Abstract

Experiments were conducted on a cylinder-induced shock-wave/boundary-layer interaction (SBLI) at Mach 6. The state of the interaction was brought through transition using a combination of boundary-layer trips and Reynolds number sweeps. The unit Reynolds number was varied over a range of 2 to 8 million per meter (M/m). The Actively Controlled Expansion wind-tunnel nozzle boundary layers transitioned near , which resulted in a threefold increase in the freestream disturbances. Trends related to SBLI properties (including the size of the separation region, peak surface heating, and surface pressure fluctuation spectra) correlated with the freestream disturbance signature. Separation distances on the centerline were bounded by laminar and turbulent conditions at and , respectively. The shape and extent of the separation region exhibited sensitivity to the transition process over a unit Reynolds number range of 3 to . Heat transfer from the reattachment shock was monitored for untripped and tripped configurations. The former demonstrated a near-linear relationship between heat transfer coefficient and unit Reynolds number, whereas the transitional SBLI configuration revealed a sudden rise in heat transfer coefficient that mirrored that of the freestream disturbances near . PCB® and Kulite® pressure transducers measured increased surface pressure fluctuations near for all model configurations, with the cylinder exciting a 40 kHz instability that led to SBLI transition for the tripped configuration.