.______     ______    __    __  .___________.
|   _  \   /  __  \  |  |  |  | |           |  _     _
|  |_)  | |  |  |  | |  |  |  | `---|  |----`_| |_ _| |_
|   _  <  |  |  |  | |  |  |  |     |  |    |_   _|_   _|
|  |_)  | |  `--'  | |  `--'  |     |  |      |_|   |_|
|______/   \______/   \______/      |__|

BOUT++ is a framework for writing fluid and plasma simulations in curvilinear geometry. It is intended to be quite modular, with a variety of numerical methods and time-integration solvers available. BOUT++ is primarily designed and tested with reduced plasma fluid models in mind, but it can evolve any number of equations, with equations appearing in a readable form.

For example, the following set of equations for magnetohydrodynamics (MHD):

can be written simply as:

ddt(rho) = -V_dot_Grad(v, rho) - rho*Div(v);
ddt(p)   = -V_dot_Grad(v, p) - g*p*Div(v);
ddt(v)   = -V_dot_Grad(v, v) + (cross(Curl(B),B) - Grad(p))/rho;
ddt(B)   = Curl(cross(v,B));

The full code for this example can be found in the orszag-tang example.

Jointly developed by University of York (UK), LLNL, CCFE, DCU, DTU, and other international partners. See the Git logs for author details.

Homepage found at http://boutproject.github.io/

• Requirements
• Usage and installation
• Terms of use
• Contributing
• License

BOUT++ needs the following:

• A C++20 compiler
• MPI
• NetCDF

BOUT++ has the following optional dependencies:

• FFTW3 (strongly recommended!)
• SUNDIALS: CVODE, IDA, ARKODE
• PETSc
• ADIOS2
• SLEPc
• LAPACK
• OpenMP
• Score-p (for performance diagnostics)

Please see the users manual.

BOUT++ is released under the LGPL, but since BOUT++ is a scientific code we also ask that you show professional courtesy when using this code:

1. Since you are benefiting from work on BOUT++, we ask that you submit any improvements you make to the code to us by submitting a pull request to this repository
2. If you use BOUT++ results in a paper or professional publication, we ask that you send your results to one of the BOUT++ authors first so that we can check them. It is understood that in most cases if one or more of the BOUT++ team are involved in preparing results then they should appear as co-authors.
3. If you use BOUT++ in your work, please help ensure that all the authors get the credit they deserve by citing BOUT++, preferably using the DOI of the version you used. See the file CITATION.cff for details. In addition, you may also cite either of the two main papers: B. Dudson et al, Comp. Phys. Comm. 2009, and B. Dudson et al, Phys. of Plasmas 2016

You can convert the CITATION.cff file into a Bibtex file as follows:

pip3 install --user cffconvert
cffconvert -if CITATION.cff -f bibtex -of CITATION.bib

See CONTRIBUTING.md and the manual page

Copyright 2010-2026 BOUT++ contributors

BOUT++ is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

BOUT++ is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

A copy of the LGPL license is in LICENSE. Since this is based on (and refers to) the GPL, this is included in LICENSE.GPL.

BOUT++ links by default with some GPL licensed libraries. Thus if you compile BOUT++ with any of them, BOUT++ will automatically be licensed as GPL. Thus if you want to use BOUT++ with GPL non-compatible code, make sure to compile without GPLed code.