fowt-force-gen 0.1.0

A package to use OpenFAST to simulate a floating wind turbine at a certain location

FOWT Force Gen

The entirety of this package is designed to generate force demands and platform motions for a floating offshore wind turbine (FOWT) modeled in a particular location, then export these data to MAT files. These MAT files are formatted in a particular way to be readable by MATLAB code used in my other GitHub repository, Rel-Opt. This package relies on NOAA's National Buoy Data Center for wind and wave resources, and uses NREL's OpenFAST software to generate the FOWT response.

Aspects of this package provide broader use that isn't reliant on Rel-Opt. Different parts of this package are capable of:

• Gathering wind and wave data at specific geographic coordinates
• Quickly generated OpenFAST files, either in isolation or in bulk
• Generating a MoorDyn file with proper platform rigid body modes and frequencies for a water depth
• Parsing OUTB files from previous OpenFAST simulations

Installation

Requirements

Python 3.6 or higher, with the standard library and the following modules:

• numpy
• scipy
• pandas
• beautifulsoup4
• requests
• windrose
• lxml

To use the full functionality of the software, the following are also required (examples are included that do not require these programs):

• OpenFAST v2.3.0 or higher
• TurbSim
  • This is included in the OpenFAST repository, but must be compiled independently

An internet connection is also required to access the National Buoy Data Center website.

Install via pip

This package can be downloaded from PyPI and installed using:

$ pip install fowt_force_gen

Setup

After installation, the full file paths to the OpenFAST and TurbSim executables must be specified in the fast_file_path.txt and turbsim_file_path.txt files, respectively, located in the fowt_force_gen root directory (this path can be found from command line using pip show fowt_force_gen).

Running the Program

Note: if testing this package without OpenFAST/TurbSim installed, skip down to Examples without OpenFAST or TurbSim.

To run the entire program sequence (including OpenFAST and TurbSim), the following information needs to be provided:

• Latitude/longitude in decimal degrees
• Platform type (currently only works with the OC4-DeepCwind platform, though functionality with the OC3-Hywind platform is in development)
• Root of the filename desired for the output MAT and CSV files.

Due to dependencies on included data files, this package must be run from the root directory as specified by pip show fowt_force_gen. Directory-agnostic operation will be included in a forthcoming release.

For example, for a OC4-DeepCwind site located at 40° 6' N, 125°, at the command line at the package root directory, type

$ python -m fowt_force_gen.fowt_force_gen --latitude 40.1N --longitude 125W --platform OC4 --fileroot Site1

The package will generate:

• Site1_bin_probabilities.csv in the current directory, indicating the probability of wind coming at each speed and direction

• Two sets of MAT files of format Reliability_Results_Site1_##mps_##deg_Climate#.mat and Surge_Site1_##mps_##deg_Climate#.mat, located in a force_gen folder within the current directory.

  • The sections of the filenames indicated by ## symbols preceding mps and deg indicate the wind speed (in m/s) and direction (clockwise starting from north), respectively, and the # symbol proceeding Climate indicates the wave climate specified. Wave climates can be specified based on user input after the monthly wave data is displayed:

  

Examples without OpenFAST or TurbSim

Due to the length of time it takes OpenFAST to run, it is recommended to run these examples that do not require OpenFAST or TurbSim. Again, these examples must be run from the package root directory as specified by pip show fowt_force_gen.

Example 1: pre_fast

This command generates all needed OpenFAST and TurbSim input files for the given geographic coordinates. The mooring system tuning step (which requires OpenFAST as well) is skipped; a pre-tuned MoorDyn file is used instead. This is effectively the entire procedure to setup for the main OpenFAST operation (as the name suggests).

To analyze an offshore site with the OC4-DeepCwind platform off the northern California coast (using NOAA Station 46014 as the reference), type

$ python -m fowt_force_gen.pre_fast -lat 39N -lon 124W -pf OC4 -fr _ -ex 1

After a few moments, monthly wave data will be displayed on the console, with user input prompts to split the analysis into multiple wave climates based on the data. If "no" is selected at the prompt, a different wave climate will be made for each month (this will result in a LOT of created files and is not recommended unless intentional—answer "yes" and make 1 or 2 custom wave climates for now).

The generated OpenFAST and TurbSim files will be created in the force_gen and turbsim_files directories, respectively. An example1_bin_probabilities.csv will be created in the root directory as well.

General use: fowt_force_gen.pre_fast can be run with the tuning step included by removing the -ex 1 argument and specifying a file root for the -fr argument. Note that this step requires OpenFAST and TurbSim.

Example 2: post_fast

This command generates the MAT files from a set of OpenFAST output files, generated after the main OpenFAST operation would ordinarily finish. A small set of the output files generated from running Example 1 in OpenFAST is included in this package as an example. At the command line, type

$ python -m fowt_force_gen.post_fast -dir example_files/post-fast

The generated MAT files will be created in the force_gen directory.

General use: Any directory can be specified for the -dir parameter as long as the directory contains at least one .outb file and three .MD.Line#.out files, all with the same filename.

Example 3: buoy

This command finds the nearest NOAA buoy to the entered coordinates, and optionally saves recently archived wind, wave, and current data to text files in the root directory.

For example, if broadly searching for data in the Gulf of Mexico (centered at about 25°N, 90°W), type

python -m fowt_force_gen.buoy -lat 25 -lon -90 -r 5000 -w

This will identify the nearest buoy via the command prompt (NOAA Station 42001 at time of writing, though this may changed due to buoy drift or new installations). Including the -w parameter writes up to three text files, one each for archived metocean, wind, and current data, though fewer may be written if data is unavailable (for Station 42001, all three are generated).

General use: The -r can be changed to any value between 1 and 9999 for smaller or larger scale searches (it can also be excluded, with 1000km as the default). Removing the -w parameter will still give the nearest buoy number in the command prompt.

Example 4: filegen

This command generates a new OpenFAST or TurbSim input file from an existing file, while changing the specified OpenFAST/TurbSim parameters within the file. This is useful for scripting, when batches of input files must be made over a range of modeling conditions.

For an existing OpenFAST input file located at %root%/example_files/example4.dat, type

python -m fowt_force_gen.filegen --input example_files/example4.dat --output example4_new.dat --param GenDOF False --numparam BlPitch 1 90 2 45 3 30

To generate a new file named example4_new.dat with GenDOF changed to False, BlPitch(1) changed to 90, BlPitch(2) changed to 45, and BlPitch(3) changed to 30 (note: changing the blade pitch like this for an actual simulation is a bad idea).

General use: filegen can be used for any .fst, .dat, or .inp file in the typical OpenFAST format. Since the MoorDyn module uses a different file format, add a -md argument to the command call if modifying a MoorDyn .dat file.

License

MIT License

Copyright (c) 2020 Software Development for Engineering Research

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.