Vortex Ring Formation Following Shock Wave Diffraction in Low-Pressure Environments

Compressible vortex rings have been widely investigated for decades under ambient atmospheric conditions, and understanding this transient phenomenon is important for improving the thrust vector and avoiding surface impingement and contamination. However, how the vortex ring behaves in a reduced pressure environment remains unknown. This work provides schlieren imaging and pressure measurement results of the vortex ring when the environmental pressure is lower than 1 atm. The basic structure of the compressible vortex ring in low-pressure environments has been captured. The reduced environmental pressure will degenerate the internal flow structure, including the shock wave, the CRVRs, and the vortices due to the Kelvin–Helmholtz instability, which is consistent with the conclusion of previous numerical work. The vortex ring is confirmed to exist when the environmental pressure is approximately 1.0 kPa.