Three-component turbulence measurements and analysis of a supersonic, axisymmetric base flow

The wake formed behind an axisymmetric body aligned with a Mach 2.49 freestream is studied experimentally using non-time-correlated stereoscopic particle image velocimetry (S-PIV), which simultaneously measures all three components of velocity in a two-dimensional plane. To obtain high-resolution data of the entire near-wake flow field, two overlapping measurement fields of view were simultaneously obtained and merged together. The quality of these data is validated using an extensive global experimental uncertainty analysis, and comparisons are drawn and discussed with previous reference laser Doppler velocimetry data of the same flow field. Turbulence statistics were derived from the S-PIV measurements, including all six independent components of the kinematic Reynolds stress tensor, as well as their isotropic and anisotropic tendencies, and fluctuating velocity triple products. These statistics revealed clear spatial trends of dominant turbulence mechanisms, including a well-defined region of fluid entrainment from the recirculation region into the shear layer near the rear stagnation point. A modified turbulent quadrant analysis method was also used, which revealed a clear organization and consistency to the turbulence structure throughout a large portion of the measured flow field.