Recompression shock unsteadiness in supersonic blunt-base cylinder wakes

A study of the unsteadiness in the position and angle of the recompression shock in supersonic blunt-body cylinder wakes at 0° and 10° angle-of-attack has been undertaken. The shock is visualized by planar Mie scattering, allowing the position of the shock to be determined instantaneously over a wide region of the flow. The recompression shock at 0° angle-of-attack is highly branched, with generally low values indicated for the density gradient across the shock. The shock is much more easily visualized at α=10°, with far less branching. The behavior of the angle-of-attack shock system shows significant variation with circumferential location. In the windward and lateral parts of the wake, the shock has many curved sections, which are often associated with large-scale turbulent structures. The leeward shock system is more stable and linear. The standard deviation in the shock position measured normal to the shock ranges from 10-13% of the base radius for the axisymmetric wake to 1-4% of the base radius for the angle-of-attack wake, with significant differences between the different planes of the angle-of-attack wake. Correlation analysis for the α=10° case indicates that fluctuations in the shock position tend to be correlated over relatively long streamwise distances. Analysis of the shock angle for the angle-of-attack wake shows a significant variation in the local angle of the shock, with the trends for the unsteadiness in the local shock angle paralleling those seen for the unsteadiness in the shock position.