A quantitative study of the interaction of two Richtmyer–Meshkov-unstable gas cylinders

• Published in: Physics of fluids (1994) 2003-04, Vol.15 (4), p.986-1004
• Main Authors: Tomkins, C., Prestridge, K., Rightley, P., Marr-Lyon, M., Vorobieff, P., Benjamin, R.
• Format: Article
• Language: English
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.1555802

We experimentally investigate the evolution and interaction of two Richtmyer–Meshkov-unstable gas cylinders using concentration field visualization and particle image velocimetry. The heavy-gas ( SF 6 ) cylinders have an initial spanwise separation of S/D (where D is the cylinder diameter) and are simultaneously impacted by a planar, Mach 1.2 shock. The resulting flow morphologies are highly reproducible and highly sensitive to the initial separation, which is varied from S/D≈1.2 to 2.0. The effects of the cylinder–cylinder interaction are quantified using both visualization and high-resolution velocimetry. Vorticity fields reveal that a principal interaction effect is the weakening of the inner vortices of the system. We observe a nonlinear, threshold-type behavior of inner vortex formation around S/D=1.5. A correlation-based ensemble-averaging procedure extracts the persistent character of the unstable flow structures, and permits decomposition of the concentration fields into mean (deterministic) and fluctuating (stochastic) components.