Base-bleed experiments with a cylindrical afterbody in supersonic flow

The effect of base bleed on the near-wake flowfield of a cylindrical afterbody in a Mach 2.5 flow with a unit Reynolds number of 45 X 10⁶ m^-1 has been investigated. This study is aimed at better understanding the complex fluid-dynamic interactions occurring in the near wake due to base bleed and is motivated by the lack of detailed velocity and turbulence data in this flowfield. The experimental techniques used include static pressure measurements along the afterbody and the base plane, schlieren and shadowgraph photography, and centerline traverses in the near wake using two-component laser Doppler velocimetry. Results indicate relatively uniform radial pressure profiles across the base plane. With increasing bleed flow rate, the average base pressure is found to increase initially, attain a peak value near an injection parameter of I = 0.0148, and then decrease with further increase in I. The optimum bleed condition near I = 0.0148 is also characterized by a weak corner expansion, a minimum value of the free-shear-layer angle, and the near-disappearance of the recirculation region (reverse velocity) along the centerline of the near wake.