engleski

Micro-fluid Dynamics via Laser- Matter Interaction: I. Vortex Filament Structures, Helical Instability, Reconnection, Merging, and Undulation

Laser-shock accelerated fluid relating to the Richtmyer-Meskhow flow environment was generated on the rippled surface of Indium target ; the supersonic oscillatory shock caused baroclinic deposition of vorticity and subsequent self-organization into vortex filaments and the family of related phenomena. Vortex filaments, characteristic of the late phase of the baroclinic vorticity evolution, appear organized into bundles ; some filaments of the bundles show helical instability, and others show reconnection ; both phenomena dominante at the laser energy density of 5J/cm^2. Vortex filaments merging, characteristic of the very late phase, accompanied by stratification of merged filaments, and undulations along the stratified sheet were observed. These self-organized (SO) structures were favorably compared with those obtained by the numerical simulation that takes into account viscosity dissipation, thermal transport..., as performed by Zabusky and the VIZILAB group. Unexpectedly, at some places of the stretched vortex sheet undulations pass into wrinkling and crumpling caused by inhomogeneous stretching and compression of the stratified sheet. This suggests the nonuniform vorticity deposition at the slow/fast interface by the irregular oscillatory shock, and the subsequent nonlinear vorticity evolution, appearing to be dominant at the higher energy density of 6J/cm^2.

laser ablation; 68.10m fluid surfaces; fluid-fluid interfaces; 47.0 fluid dynamics

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