Near wake of a blunt body at hypersonic speeds

An experimental investigation was conducted to determine the characteristics of the near wake of a blunt body in hypersonic flow. Base-pressure and body-surface pressure measurements are combined with hot-wire and pitot-pressure data to describe the free shear layer, the base-flow region, the recompression zone, and the initial development of a laminar wake. It is found that the postulate of thin shear layers is valid for Reynolds numbers greater than about 104, if the Mach number Me external to the shear layer is not large. Detailed measurements with a steady-state hot-wire behind a two-dimensiona l circular cylinder indicate that the maximum pressure rise occurs downstream of the stagnation point formed by the merging shear layers. The hot-wire measurements are corroborated by base-pressure data obtained with cylinders and wedges. Comparison between the experimental and theoretical results points out the importance of the base-flow temperature and the initial shear-layer profile in determining the observable characteristics of the near wake.