OpenFAST Turbine Models

This repository contains turbine aeroservoelastic models developed for research activities at the National Renewable Energy Laboratory (NREL).

NREL researchers should refer to the internal repository at https://github.nrel.gov/NWTC/openfast-turbine-models.

Overview of Design Process

The design process involves rescaling an existing reference wind turbine (RWT) to have specified turbine characteristics and then optimizing the resulting geometry.

Software Stack

• WISDEM -- uses OpenMDAO to optimize a turbine geometry for realistic aeroelastic performance subject to appropriate system constraints; includes numerous submodels, e.g., CCBlade for blade-element momentum theory aerodynamic analysis and pyFrame3DD for structural analysis
• WEIS -- performs multi-fidelity co-design with a time-domain aeroservo[hydro]elastic solver, OpenFAST, in the loop
• OpenFAST -- individual turbine or wind-farm model (FAST.Farm); can simulate steady or turbulent inflow; structural analysis may be performed by ElastoDyn (Euler-Bernoulli beam theory) or BeamDyn (geometrically exact beam theory)
• ROSCO -- reference open-source controller that may be used in OpenFAST (specified as a "Bladed-style DLL" controller in ServoDyn); when compiled, produces a libdiscon.so controller that uses a specified DISCON.IN file

Input/Outputs

• Inputs to WISDEM include a universal geometry file (described here) in YAML format, analysis options file (described here, and a modeling options file (described here).

  • Every time WISDEM is run, a new geometry YAML file is produced.
  • WISDEM may be run without any optimizations turned on in order to access all the derived quantities of interest (a full list of outputs is found here).

• Inputs to WEIS are similar to WISDEM, including geometry, analysis options, and modeling options YAML files. Outputs include OpenFAST time-domain simulation data and necessarily include a functional OpenFAST model (that may be independently run, outside of WEIS).

Getting Started

The design process depends on the tools in the WISDEM Interface package. Users should start by installing WISDEM and WEIS (develop) in separate clean Python environments. While WEIS depends on WISDEM, the current develop branch tracks an older version of WISDEM and using the latest stable version of WISDEM is not a bad idea. In addition, WiSDEM and WEIS have different dependencies, so the package will be easier to install if conda/mamba does not need to resolve all dependencies simultaneously. The use of mamba is recommended as it is both more robust (at solving for package dependencies) and is computationally much more efficient.

The WISDEM workflow is generally as follows:

1. Identify an appropriate starting turbine geometry (e.g., an IEA RWT)
2. Update turbine geometry file with known properties (e.g., rated power, hub height, rotor speed range, ...)
3. Run design_workflow.py or submit mpi_design_workflow.slurm (appropriately modified for your high-performance computing environment) to your job scheduler
4. Run the resulting compare_TURBINENAME_designs.py, verify convergence of optimization steps and sanity check the resulting optimized turbine properties.
5. Adjust optimization parameters in design_workflow.py and re-run if needed.

Using the resulting optimized turbine geometry from WISDEM, the WEIS workflow is generally as follows -- workflow under development:

1. Run a power-curve sweep, verify that WISDEM performance can be replicated
2. Optimize the ROSCO pitch controller
3. Run additional design load cases for additional sanity checks

As a final step, designers may wish to linearize the openfast model determine eigenvalues for a detailed structural dynamics analysis.