Characterization of Near Wake Flow Behind a Circular Cylinder in High Supersonic Flow Using High-Fidelity Simulations

This paper characterizes the near wake flow behind a circular cylinder at high speeds using transition correlations and the variation of mean shear layer reattachment length with Reynolds number. High-fidelity numerical simulations are performed at M1 = 4 for 2.1 × 10^4 ≤ Re1D ≤ 5 × 10^5 and compared with existing supersonic/hypersonic near wake experiments, and laminar theories. The results showed that the near wake remains laminar for Re1D ≲ 10^5. At higher Reynolds numbers, transition moves upstream from the far wake into the near wake region, accompanied by a reduction in reattachment length. The paper highlights possible causes of discrepancies in reattachment length between DNS simulations and experiments at similar Reynolds numbers and proposes that reattachment length can be a reliable indicator of near wake state. These findings provide a basis for understanding and interpreting near wake oscillations observed in recent investigations of Schmidt and Shepherd.