Characteristics of a central bleed jet in supersonic axisymmetric base flow

The near-wake flow structure of a supersonic axisymmetric base flow with base bleed is investigated in detail using acetone planar laser-induced fluorescence. Global side-view and end-view images are analyzed to detect unstirred bleed fluid, which has been found to persist from the bleed orifice through reattachment (i.e., rear stagnation point). The characteristic size, shape, and location of the bleed fluid pockets are studied. This enables a comparison of the bleed jet structure for three different cases of mass flow rate of bleed fluid. In addition, the average location of the forward stagnation point and the primary and secondary recirculation regions are linked to the distributions of several statistics. The similarities and differences between two suboptimal bleed rate cases identify possible optimal locations for the central bleed jet to be directed. A stabilizing effect caused by increasing bleed rate is documented in many of the statistical quantities. Agreement between side-view and end-view image analysis confirms the ability of the processing technique to distinguish the unstirred bleed fluid in all images.