Supersonic base flow experiments in the near-wake of a cylindrical afterbody

The near-wake of a circular cylinder aligned with a uniform Mach 2.5 flow has been experimentally investigated in a wind tunnel designed solely for this purpose. Mean static pressure measurements were used to assess the radial dependence of the base pressure and the mean pressure field approaching separation. In addition, two-component laser Doppler velocimeter (LDV) measurements were obtained throughout the near-wake including the large separated region downstream of the base. The primary objective of the research was to gain a better understanding of the complex fluid dynamic processes found in supersonic base flowfields including separation, shear layer development, reattachment along the axis of symmetry, and subsequent development of the wake. Results indicate relatively large reverse velocities and uniform turbulence intensity levels in the separated region. The separated shear layer is characterized by high turbulence levels with a strong peak in the inner, subsonic region which eventually decays through reattachment as the wake develops. A global maximum in turbulent kinetic energy and Reynolds shear stress is found upstream of the reattachment point which is in contrast to data from the reattachment of a supersonic shear layer onto a solid wall.