BOUT++: A framework for parallel plasma fluid simulations*

A modular code for the solution of 3D fluid equations in curvilinear coordinates is presented. Aimed at simulating Edge Localised Modes (ELMs) in tokamak x-point geometry, the code is able to simulate a wide range of fluid models (magnetised and unmagnetised) involving an arbitrary number of scalar and vector fields. Time evolution is fully implicit, and 3rd-order WENO schemes are implemented for accurate capturing of shocks. Benchmarks are presented for linear and non-linear problems (the Orszag-Tang vortex) showing good agreement. Performance of the code is tested by scaling with problem size and processor number. Linear and non-linear simulations of ELMs are presented, and compared to the linear ELITE code. These initial results, show that BOUT++ recovers many of the features expected from analytic theory of peeling-ballooning modes.