Chatwood Labs Releases Open-Source BOUT++ Grid Generator

Chatwood Labs has released an open-source axisymmetric tokamak grid generator for BOUT++ 5.x, marking the first public tooling release from the company’s internal simulation stack.

The release follows the completion of initial reduced-order validation studies and the move into higher-dimensional MHD modelling. As Chatwood Labs expanded into BOUT++-based workflows, the need for robust, well-documented grid generation tooling became increasingly clear. Rather than keeping that capability internal, the company has chosen to publish it as part of its broader commitment to transparent technical development.

The generator produces axisymmetric tokamak geometry grids directly compatible with BOUT++ 5.x environments. It supports both circular cross-sections and shaped equilibria through elongation (κ) and triangularity (δ) parameters, covering configurations from simple reference cases through to ITER-scale shaped plasmas.

The tool computes coordinate mappings, full metric tensor components, the Jacobian, magnetic geometry, and field-aligned shift angles. It also provides three curvature modes: exact numerical differentiation using Christoffel symbols, a fast large-aspect-ratio analytic approximation, and a disabled mode for cases where curvature terms are not required.

Version 1.2.0-Public ships with three example configurations: a circular reference tokamak for verification and algorithm testing, an ITER-inspired shaped geometry with κ = 1.7 and δ = 0.33, and an extreme shaping stress-test case with κ = 2.2 and δ = 0.5 designed to push solver stability and metric calculation robustness near the limits of the geometry model.

The grid generator is released under the MIT Licence and is now available through the Chatwood Labs GitHub repository. A companion grid diagnostics and validation utility is planned as a separate public release, extending the company’s open tooling around geometry verification and simulation readiness.

Based in Greater Manchester, Chatwood Labs is building its research programme around simulation, control architecture, and staged technical validation, with open technical tooling forming part of that effort.