Time-correlated visualizations of supersonic blunt-base cylinder wakes

Time-correlated imaging has been used to study supersonic blunt-base cylinder wakes at 0° and 10° angle-of-attack to an M=2.46 flow. Most of the evolution of the large-scale structures consists of swelling, shrinking, or rollover, with interactions between structures seeming to play a small role. While structures occasionally merge, rotational pairing events are not observed in the visualizations; this is in stark contrast to typical large-scale structure development in incompressible shear layers. A consistent difference in the structure convection velocity exists between the high-speed and low-speed sides of the shear layers in this study. End-view visualizations show that the large-scale structures have a significant circumferential velocity component in the angle-of-attack wake during and after reattachment, while the large-scale structures in the axisymmetric wake do not. The position and area of the wake core in both wakes vary on a relatively short timescale (around 20 μs) in the trailing wake. The position of the recompression shock in the windward part of the angle-of-attack wake appears to fluctuate on similar timescales, with disturbances in the shock position tending to follow the convection of large-scale structures in the adjoining shear layer.