Mechanism of longitudinal magnetic field suppressed Richtmyer-Meshkov instability

Abstract

Based on the ideal magneto-hydro-dynamic equations (MHD) and adopting the CTU (Corner Transport Upwind) + CT (Constrained Transport) algorithm, the Richtmyer-Meshkov (RM) instability of the Gaussian distribution R22 gas column generated by the interaction of a planar shock wave with the gas column in the presence of magnetic field is investigated numerically. The numerical results show that the evolution of shock wave structure and interface instability during the interaction between shock wave and gas column are consistent with the experimental results of Haas and Sturtevant (Hass J F, Sturtevant B 1987 <i>J. Fluid Mech</i>. <b>181</b> 41) in the absence of a magnetic field. In the presence of a longitudinal magnetic field, the evolution of the shock structures is almost unaffected, while the density interface appears very smooth and interfacial vortex sequences vanish, which is a clear indication of the RMI suppresion. Moreover, as the shock wave impinges on the interface, the magnetic field lines refract on the interface, resulting in the generation of magnetic field gradient in the flow field, which is not consistent with the scenario in the above case. As a result, a stronger magnetic tension is produced on the inner and outer vorticity layer. Simultaneously, the magnetic tension produces a moment on the interface fluid, which is opposite to the rolling direction of the velocity shear. Therefore, the interface instability and the main vortex rolling-up are effectively suppressed. In addition, the non-uniform distribution of magnetic tensions along the interface changes the aggregation degree of the magnetic lines, amplifying the magnetic strength, and finally enhancing the suppression effect of the magnetic field on the interface instability.