Nautilus: Robust, positivity and divergence preserving code for multi-fluid, multi-species electromagnetics and plasma physics applications

In this paper we will present algorithms implemented in Nautilus, a new code for the solution of a wide variety of plasma and neutral fluid equations. Nautilus can simulate fully and weakly ionized flows and has been applied to fast magnetohydrodynamics (MHD) devices like Z-pinches and dense-plasma focuses, chemically reacting hypersonic flows and plasma jet propagation and merging for the creation of high energy-density states in the laboratory. We present details of new positivity preserving fluid algorithms as well as collocated Maxwell equation solvers that preserve divergence and work on general geometries. Current state of Nautilus is described and future directions outlined.