Vortex morphologies on reaccelerated interfaces: Visualization, quantification and modeling of one- and two-mode compressible and incompressible environments

We examine the vortex dynamics and interfacial evolution of "reacceleration " and "reshock" for single interface density-stratified fluid (Richtmyer-Me shkov) environments. In the former case, we simulate, visualize, and quanti fy the parameter range of the free falling tank laboratory experiment of J. Jacobs and C. F. Niederhaus, where the impulsive subsequent acceleration o f the interface occurs after several rolls from the initial impulsive accel eration. We interpret the rapid onset of chaotic motion in the roll-up regi on as due to the formation of intertwined close-laying layers of opposite-s igned vorticity. In the latter case, we make compressible simulations at lo w Mach number (M=1.2) and compare with incompressible simulations. We juxta pose the results and find an excellent agreement in large and intermediate size features and their magnitudes before the "reshock." At the "reshock," discrepancies arise due to highly compressible regime. The simulations were made with incompressible vorticity-based methods, vortex-in-cell (VIC) and vortex blob (VB), and compressible second-order Godunov codes. (C) 2000 Am erican Institute of Physics. [S1070-6631(00)01112-0].