OpenFAST is a wind turbine simulation tool which builds on FAST v8. It was created with the goal of being a community model developed and used by research laboratories, academia, and industry. It is managed by a dedicated team at the National Renewable Energy Lab. Our objective is to ensure that OpenFAST is sustainable software that is well tested and well documented. If you'd like to contribute, see the Developer Documentation and any open GitHub issues with the Help Wanted tag.

OpenFAST is under active development.

The transition from FAST v8 to OpenFAST v0.1.0 represents the effort to better support an open-source developer community around FAST-based aero-hydro-servo- elastic engineering models of wind-turbines and wind-plants. OpenFAST is the next generation of FAST analysis tools. More information is available in the transition notes.

FAST v8 is a computer-aided engineering tool for simulating the coupled dynamic response of wind turbines. FAST joins aerodynamics models, hydrodynamics models for offshore structures, control and electrical system (servo) dynamics models, and structural (elastic) dynamics models to enable coupled nonlinear aero- hydro-servo-elastic simulation in the time domain. The FAST tool enables the analysis of a range of wind turbine configurations, including two- or three-blade horizontal-axis rotor, pitch or stall regulation, rigid or teetering hub, upwind or downwind rotor, and lattice or tubular tower. The wind turbine can be modeled on land or offshore on fixed-bottom or floating substructures. FAST is based on advanced engineering models derived from fundamental laws, but with appropriate simplifications and assumptions, and supplemented where applicable with computational solutions and test data.

The aerodynamic models use wind-inflow data and solve for the rotor-wake effects and blade-element aerodynamic loads, including dynamic stall. The hydrodynamics models simulate the regular or irregular incident waves and currents and solve for the hydrostatic, radiation, diffraction, and viscous loads on the offshore substructure. The control and electrical system models simulate the controller logic, sensors, and actuators of the blade-pitch, generator-torque, nacelle-yaw, and other control devices, as well as the generator and power-converter components of the electrical drive. The structural-dynamics models apply the control and electrical system reactions, apply the aerodynamic and hydrodynamic loads, adds gravitational loads, and simulate the elasticity of the rotor, drivetrain, and support structure. Coupling between all models is achieved through a modular interface and coupler.

The full documentation is available at http://openfast.readthedocs.io/.

This documentation is stored and maintained alongside the source code. It is compiled into HTML with Sphinx and is tied to a particular version of OpenFAST. Readthedocs hosts the following versions of the documentation:

• latest - The latest commit on the master branch
• stable - Corresponds to the last tagged release
• dev - The latest commit on the dev branch

These can be toggled with the v: latest button in the lower left corner of the docs site.

OpenFAST is hosted entirely on GitHub so you are in the right place! The repository is structured with two branches following the "git-flow" convention:

• master
• dev

The master branch is stable, well tested, and represents the most up to date released version of OpenFAST. The latest commit on master contains a tag with version info and brief release notes. The tag history can be obtained with the git tag command and viewed in more detail on GitHub Releases. For general use, the master branch is highly recommended.

The dev branch is generally stable and tested, but not static. It contains new features, bug fixes, and documentation updates that have not been compiled into a production release. Before proceeding with new development, it is recommended to explore the dev branch. This branch is updated regularly through pull requests, so be sure to git fetch often and check outstanding pull requests.

For those not familiar with git and GitHub, there are many resources:

• https://guides.github.com
• https://try.github.io
• https://help.github.com/categories/bootcamp/
• https://desktop.github.com/
• http://nvie.com/posts/a-successful-git-branching-model/

Details for compiling compiling, using, and developing OpenFAST on Unix-based and Windows machines are available at readthedocs.

Please use GitHub Issues to:

• ask usage questions
• report bugs
• request code enhancements

For other questions regarding OpenFAST, please contact Mike Sprague.

Users and developers may also be interested in the NREL National Wind Technology Center (NWTC) phpBB Forum.

OpenFAST is maintained and developed by researchers and software engineers at the National Renewable Energy Laboratory (NREL), with support from the US Department of Energy's Wind Energy Technology Office. NREL gratefully acknowledges development contributions from the following organizations:

• Envision Energy USA, Ltd
• Brigham Young University
• Intel® Parallel Computing Center (IPCC)