A Particle Image Velocimetry Study of Richtmyer-Meshkov Instability in a Twice-Shocked Heavy Gas Cylinder
National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, Mianyang 621999, China
The Richtmyer-Meshkov (RM) instability in a twice-shocked heavy gas (SF6) cylinder surrounded by ambient air is experimentally studied using the particle image velocimetry (PIV) technique, and the velocity and vorticity fields as well as the circulation of the flow are quantitatively characterized. The results show that after the first shock-interface interaction, the evolution of the interface is dominated by the formation of a primary vortex pair, whose strength undergoes little change over a relatively long time; but after a reshock, for a short endwall distance, a secondary vortex pair, with its rotation opposite to the primary vortex pair, is formed whose strength is significantly weaker than that of the primary vortex pair, while, for a long endwall distance, no large scale vortex structure is formed. The circulation of the primary vortex pair decreases over time after the reshock, which suggests that the energy is being transferred from the large scale structures to the smaller ones in the flow. The circulations of the primary and secondary vortex pairs are remarkably consistent with the predictions by the theoretical models.