Streamwise Vortex Instability and Transition on the Hyper-2000 Scramjet Forebody

摘要

Despite the closely coupled multidisciplinary design of hypersonic airbreathing vehicles, the boundary-layer transition mechanisms that are important on the forebody ahead of the scramjet inlet are not well understood. Transition induced by the growth of streamwise vortices on a scramjet forebody geometry is investigated. Characteristics of the separation zone near the first compression corner are visualized with oil-flow experiments. These experiments also reveal the presence of regularly spaced streamwise vortices on the compression ramp even in the absence of controlled disturbance generators. The growth and decay of these vortices are inferred from the heat-transfer rates measured using temperature-sensitive paints. The streamwise vortices are enhanced in a controlled and repeatable manner by wrapping tapes around the leading edge. The vortices grow significantly on the second compression ramp and then decay, suggesting transition onset. The disturbance growth seems to show a systematic trend with unit Reynolds number, although this trend was not consistently seen for all cases. For some of the cases, the disturbances showed the largest growth when the roughness spacing was close to the vortex spacing seen in the oil-flow images.