NREL has sponsored the development, verification, and validation of various codes for prediction of wind-turbine loads and responses.  A streamlined code was developed through a subcontract between NREL and Oregon State University.  This code, called FAST (Fatigue, Aerodynamics, structures, and Turbulence), can be used to model both two- and three- bladed, horizontal-axis wind turbines.

The FAST code models the wind turbine as a combination of rigid and flexible bodies.  For example, two-bladed, teetering-hub turbines are modeled as four rigid bodies and four flexible ones.  The rigid bodies are the earth, nacelle, hub, and optional tip brakes (point masses).  The flexible bodies include blades, tower, and drive shaft.  The model connects these bodies with several DOFs.  These include tower bending, blade bending, nacelle yaw, rotor teeter, rotor speed, and drive shaft torsional flexibility.  The flexible tower has two modes each in the fore-aft and side-to-side directions.  The flexible blades have two flapwise modes and one edgewise mode per blade.  One can turn these DOFs on or off individually in the analysis by simply setting a switch in the input data file.

FAST uses Kane's method to set up equations of motion, which are solved by numerical integration.  The implemented method makes direct use of the generalized coordinates, eliminating the need for separate constraint equations.  FAST uses the AeroDyn subroutine package developed by Windward Engineering to generate aerodynamic forces along the blade.

FAST is extensively documented in the FAST User's Guide.  Please refer to it for details on the use of the program.  Jason Jonkman is writing a detailed theory manual and we hope to publish it in 2006.

In 2002, Jason Jonkman and Marshall Buhl rewrote most of the code in modern Fortran.  Marshall Buhl merged the formerly separate executables for two- and three- bladed turbines and rewrote most of the I/O for the program.  Jason Jonkman rederived the fundamental equations and coded them using matrix manipulation routines instead of the original method of working directly with the individual elements of the matrices.  This has allowed him to easily add new degrees of freedom (DOFs).  Dr. David Laino of Windward Engineering made the changes necessary to interface the structural parts of FAST with the AeroDyn 12 aerodynamic routines.

In 2003, additional features were added to the code, including the ability to develop periodic linearized state matrices for controls design and the ability to use FAST as a preprocessor for generating MSC.ADAMS® datasets of wind turbine models.  Aeroacoustic noise prediction algorithms have also been introduced.

Additional features were added to the FAST code again in 2004.  New model features added include a lateral offset and skew angle of the rotor shaft, rotor-furling, tail-furling, tail inertia and aerodynamics, yaw control, and high-speed shaft (HSS) brake control.  An interface has been developed between FAST and a master controller implemented as a dynamic-link-library (DLL) in the style of Garrad Hassan's Bladed wind turbine software package.  An interface has also been developed between FAST and Simulink® with MATLAB®, enabling user's to implement advanced turbine controls in Simulink's convenient block diagram form.

Additional features were added to the FAST Code again in 2005.  These include new nacelle inertial measurement unit and tower strain gage outputs, upgrades to the simple variable-speed control model, and new support platform motion and loading functionality.  Despite the addition of six new platform motion degrees of freedom, the code was also better-optimized so that it runs 15% faster than previous versions (or faster, depending on the options being modeled).  Please see the section entitled "Upgrading to FAST v6.0 from v5.1" in the FAST User's Guide for detailed information on how to upgrade to the latest version of FAST.

To verify FAST, we compared it to MSC.ADAMS using several different turbine models and for many different conditions and got very good agreement.  We created test procedures that run 17 cases of FAST and plot the results of a recently changed FAST against MSC.ADAMS results and results from the previous versions of FAST and MSC.ADAMS.  We have made PDF files of the charts for 14 of the cases and they are available for viewing from our FAST verification page.  This page also includes the abstract of a paper we presented at the 23rd ASME / 42nd AIAA Wind Energy Symposium in Reno, NV, 2004.

FAST with AeroDyn was evaluated by Germanischer Lloyd WindEnergie and found suitable for "the calculation of onshore wind turbine loads for design and certification." Electronic versions of the issued certificate and report are available for viewing.

You may download the following files from our server:

• FAST Change Log (v6.01, 205 KB, 12-August-2005)

  This is a list of changes made to the code.  Look at this text file to see if we've made worthwhile changes since you received your previous version of FAST.

• FAST User's Guide (v3.01, 1.9 MB, 12-August-2005)

  This is the FAST User's Guide.  Please refer to it when trying to understand how the program works.  Because of its large size, it is not included in the archive.

  If you want to refer to this User's Guide in a report, here is a reference for you:

  Jonkman, J. M.; Buhl Jr., M. L. "FAST User's Guide," NREL/EL-500-29798. Golden, Colorado: National Renewable Energy Laboratory, 2005.

• FAST Archive (v6.01, 3.3 MB, 12-August-2005)

  This is a self-extracting archive of FAST.  It contains the FAST executable file, sourece code, sample input files, installation- verification test procedure, and change log.  It runs on all 32-bit Windows® platforms.  We created the executable file with Compaq Visual Fortran® v6.6.B.

If you want to refer to the FAST website in a report, here is a reference you can use:

NWTC Design Codes (FAST by Jason Jonkman).  http://wind.nrel.gov/designcodes/simulators/fast/.  Last modified 12-August-2005; accessed 12-August-2005.

Additional links:

• FAST Verification Page

  We did a verification study in which we compared FAST v4.31 to MSC.ADAMS.  An AIAA/ASME paper resulted from this study.  You can read the abstract of the paper here.  You can also view plots of the results of the verification tests we run whenever we release a new version of FAST.