AMR Simulations of the Magneto-hydrodynamic Richtmyer-Meshkov Instability.

By: Dr. Ravi Samtaney

In the past two decades the Richtmyer-Meshkov (RM) instability has become the subject of extensive experimental, theoretical and computational research due to it's importance in technological applications such as inertial confinement fusion, as well as astrophysical phenomena such as supernovae collapse. In this talk we will present recent results from nonlinear simulations of the RM instability in the presence of a magnetic field.

The seminar will be divided into two segments. In the first segment, we will present numerical evidence that the growth of the RM instability is suppressed in the presence of a magnetic field. This is due to a bifurcation which occurs during the refraction of the incident shock on the density interface. The result is that baroclinically generated vorticity is transported away from the interface to a pair of slow magnetosonic shocks. Consequently, the density interface is devoid of vorticity and it's growth and associated mixing is completely suppressed. The second segment of the talk will focus on the development of an adaptive mesh refinement (AMR) code for MHD. The code is developed using the AMR framework, CHOMBO developed at LBNL. AMR provides an effective mechanism for obtaining high spatial resolution where required thereby leading to efficient computations. The numerical method consists of an explicit "unsplit" algorithm coupled with the 8-wave upwinding method to solve the MHD equations written in strong conservation form. The solenoidal property of the magnetic field is achieved via projection which is solved on the hierarchical AMR meshes using a multi-grid technique.