Shock gaseous cylinder interactions: Dynamically validated initial conditions provide excellent agreement between experiments and numerical simulations to late–intermediate time

We present numerical simulations of a planar shock interacting with a two-dimensional sulfur hexafluoride $({\mathrm{SF}}_6)$ cylinder. We have excellent agreement with experiments at two Mach numbers $\text{M=1.095}$ [Jacobs, Phys. Fluids A 5, 2239 (1993)] and $\text{M=1.2}$ [Zoldi, Ph.D. thesis, SUNY Stony Brook, 2002]. This includes intermediate scale features and quantities such as bounding box dimensions of coherent structures and velocity magnitude distribution function. Our simulations use a validated viscous FLASH [ASCI FLASH Center, “FLASH User’s Guide,” University of Chicago, 2002] environment initialized with a cylinder bounded by a finite-thickness interfacial transition layer of specific shape. The shape parameters are determined through iteration, beginning with the uncertain experimental images and optimizing to obtain maximal agreement with early to intermediate time evolving structures. The visiometric approach and the vortex paradigm [Hawley and Zabusky, Phys. Rev. Lett. 63, 1241 (1989)] are essential to obtain insight into this Richtmyer–Meshkov environment. We verify our recent discovery [Zabusky and Zhang, Phys. Fluids 14, 419 (2002)] that after the primary shock-deposition of vorticity by the incident shock, a vortex bilayer of large circulation magnitude grows significantly through intermediate times. The inclusion of physical viscosity allows us to examine some aspects of pre-turbulence at late–intermediate times.