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-Meshkov) environments. In the former case, we simulate, visualize, and quantify the parameter range of the free falling tank laboratory experiment of J. Jacobs and C. F. Niederhaus, where the impulsive subsequent acceleration of the interface occurs after several rolls from the initial impulsive acceleration. We interpret the rapid onset of chaotic motion in the roll-up region as due to the formation of intertwined close-laying layers of opposite-signed vorticity. In the latter case, we make compressible simulations at low Mach number (M=1.2) and compare with incompressible simulations. We juxtapose 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 American Institute of Physics. [S1070-6631(00)01112-0].