Study of magnetohydrodynamic effects for the richtmyer-meshkov instability

Abstract

This work presents experimental and computational studies of the Richtmyer-Meshkov (RM) instability with Magnetohydrodynamic (MHD) effects. The experimental work does not consider the instability or its growth, but rather developes an atmospheric plasma jet for use in future magnetohydrodynamic experiments. The operating conditions of the torch are explored to optimize the ionized length of the plasma jet by varying the voltage-current characteristics and the gas low rates. Probe, spectral, and visual diagnostics are also developed in an effort to characterize the plasma. The probe diagnostics were unsuccessful but discussions are included to help improve the technique. The visual Mie-Scattering like technique is able to capture qualitative images of the plasma flow field and are ready for use in future hydrodynamic experiments where the qualitative growth is of interest. Simulations utilized the hydrocode FLAG, developed at Los Alamos National Laboratory, are performed on a 2D shock cylinder plasma-air interface where MHD effects work to remove vorticity from the interface and suppress RM growth. To study this magnetic field orientation, magnetic field strength, and incident Mach number are all varied in this study. It was found that the orientation of the magnetic fi eld relative to the shock wave direction causes different morphology and can effect the amount of observable RM suppression. Similarly, increasing the magnetic field strength reduces the effects of the baroclinic vorticity, responsible for RM growth, by generating strong MHD waves which carry the vorticity away from the interface quicker. Increasing the Mach number can also cause varying qualitative effects, with greater Mach numbers showing greater interfacial compression. But comparing the MHD RM to the RM instability at a single Mach number still shows suppresion of the instability. Finally a 3D cylindrical interface is simulated using the hydrocode ARES. These simulations compare the cylindrical Richtmyer-Meshkov to two cases of the MHD-RM instability; one with a parallel and one with a perpendicular magnetic fi eld of 500 Guass. As per literature, the magnetic cases exhibit suppression through decreased enstrophy, vorticity, and mixedness with respect to time in addition to the clear morphological differences.