Large-scale structure visualization and convection velocity in 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 temporal 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. The position of the recompression shock in the windward part of the angle-of-attack wake appears to fluctuate on rapid time scales, with disturbances in the shock position tending to follow the convection of large-scale structures in the adjoining shear layer. A consistent difference in the structure convection velocity seems to exist between the high-speed and low-speed sides of the shear layers in this study. The stream selection rule is followed for both the axisymmetric and angle-of-attack wakes before reattachment, but the recompression and reattachment processes greatly influence the structure convection velocity in the axisymmetric wake. Convection velocity measurements in the 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, as expected.