BOUT++: a framework for parallel plasma fluid simulations

TL;DR

BOUT++ is a modular, parallel simulation framework for 3D plasma fluid models in complex geometries, demonstrating accurate, scalable, and dissipationless ELM simulations in tokamak edge physics.

Contribution

This paper introduces BOUT++, a flexible, high-performance code capable of simulating a wide range of plasma fluid models in various geometries, including the first dissipationless ELM simulations.

Findings

Good agreement with benchmark problems like the Orszag-Tang vortex.

Efficient scaling to thousands of processors.

First dissipationless initial-value ELM simulations.

Abstract

A new modular code called BOUT++ is presented, which simulates 3D fluid equations in curvilinear coordinates. Although 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, in a wide range of geometries. Time evolution is fully implicit, and 3rd-order WENO schemes are implemented. 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, showing efficient scaling to thousands of processors. Linear initial-value simulations of ELMs using reduced ideal MHD are presented, and the results compared to the ELITE linear MHD eigenvalue code. The resulting mode-structures and growth-rate are found to be in good agreement (BOUT++ = 0.245, ELITE = 0.239). To our knowledge, this is the first time dissipationless, initial-value simulations of ELMs have been successfully demonstrated.